Re: [Emc-users] 3 phase power
On 12 November 2011 04:27, Dave e...@dc9.tzo.com wrote: On 11/11/2011 11:29 AM, andy pugh wrote: What would be illegal in the UK? Thinking about it, not what I said, I think. I think the regulations I was thinking of (part P) only apply to fixed installations, and we can still do anything we like at the other side of a plug. Also Part P might only apply to domestic installations. And even then you can have it inspected by Building Control, except they typically have no system to do that. So, I might well be completely wrong, as I have no idea what the rules are about tinkering with three-phase equipment. -- atp The idea that there is no such thing as objective truth is, quite simply, wrong. -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
Brian, if you use two legs of your incoming mains for a single phase supply, you will have two hot wires in these appliances plus an uncommon voltage. Using one hot leg plus neutral you will have a much safer supply with an usual voltage (for the US). Two hot legs means all switches must be double pole, and you have a 100% chance to die if you should accicentally touch parts of the circuit instead of 50%. Here in Germany, all electrical supply, home and industry, is done with three phase current plus neutral. For single phase use, like for apartments, the three phases are split up and each apartment or room gets one hot leg plus neutral (plus protective earth). Motor supplies may be built without a neutral wire because the windings can be switched in star or delta (triangle) way without needing a neutral wire in either case. If you need power for single phase devices, say, a control box or control computer, a transformer can be used to generate the usual 120 volts (US). The disadvantage is that these transformers have limited power capacity whereas a direct single mains supply has (almost) no limitations. The voltage between the outer legs is equal to: voltage between one leg and neutral times square root of three (about 1.7). If you want to do yourself something good make the investment into a fourth wire for neutral and you will be on the safe side at the least cost. In Germany (and most european countries, i think), any electrician installing a three phase supply without neutral and protective earth would be kicked out of business by law for life time instantly. Peter Blodow Brian May schrieb: Yes everything at our shop is wired off 3 phase. But our box has a nuetral. So it goes from leg to nuetral. However my machine only has 4 lines - the 3 legs of power and an earth ground. So i guess my question is do i need the nuetral? Sent from my iPod On Nov 10, 2011, at 8:59 PM, Eric Keller eekel...@psu.edu wrote: the lights and most outlets here at work are single phase wired off of 3 phase. On Thu, Nov 10, 2011 at 9:50 PM, Brian May bri...@diezorlich.com wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks Brian Sent from my iPod -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
On 11 November 2011 09:25, Peter Blodow p.blo...@dreki.de wrote: In Germany (and most european countries, i think), any electrician installing a three phase supply without neutral and protective earth would be kicked out of business by law for life time instantly. 3P + E outlets are perfectly OK in the UK. As has been hinted at elsewhere in the thread, it depends what the single-phase power is for. If it is to power DC supplies and equipment with internal PSUs like monitors, as long as universal input (120VAC-240VAC) devices are chosen, it should be no problem. -- atp The idea that there is no such thing as objective truth is, quite simply, wrong. -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
Sent from my iPod On Nov 10, 2011, at 10:30 PM, Dave e...@dc9.tzo.com wrote: Usually bigger 3 phase machines being fed with 480 volts or so will only have the 3 phases run to the machine without a neutral wire. The reason being that Line to Neutral on a 480 volt system is 277 volts and that is not very useful for anything other than lighting. To get 120 VAC, two of the phases will be tapped (480 volts) and that will be run to a step down transformer. One the secondary side of the transformer, one leg of the transformer will be declared the hot line, and the other leg will be declared the neutral. The neutral will be bonded to the ground close to the transformer. The hot line is fused.That will establish a proper 120 VAC circuit off the 3 phase input power. What is meant by bonded to the ground? Does that mean connecting the nuetral leg of the transformer to the ground? If so, why use the transformer at all when i can just go from a leg to ground? You could run a separate single phase feed into the existing 3 phase power panel, but then you would have power being fed into one panel from two different sources and that gets tricky from a safety standpoint. I try and avoid doing that whenever possible. Generally when you pull the disconnect switch on a machine panel you want to kill all power in the panel for safety. A lot of machine builders are now avoiding 120 volt power system in their machines entirely. They do that by using DC power supplies that can accept high voltage input power directly. You can buy 3 phase input power supplies that will accept up to 600 VAC and produce 24 VDC. Most of the big power supply makers sell them. Dave On 11/10/2011 10:27 PM, Brian May wrote: Ok that makes sense. Just out of curiosity, How do other machines do it. Our other cnc machines only have the 3 lines and earth ground running into them... Sent from my iPod On Nov 10, 2011, at 9:01 PM, Brian Mihulkabmihu...@hulkster.net wrote: On 11/10/2011 08:50 PM, Brian May wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks Brian Sent from my iPod -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users If its 3 phase 208, one leg to any other leg will give you 208. You have to have the neutral to get 120 from any leg. You should get 120 from any leg to ground but it wouldn't be up to code. Brian -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
On 11 November 2011 12:11, Brian May bri...@diezorlich.com wrote: What is meant by bonded to the ground? Does that mean connecting the nuetral leg of the transformer to the ground? If so, why use the transformer at all when i can just go from a leg to ground? Because that merely establishes a reference voltage for one leg of the transformer secondary, but does not cause any current to flow in the ground wire. (current flow is round the loop of the transformer secondary, and the input power currents are in the 3-phase power conductors, not the earth) -- atp The idea that there is no such thing as objective truth is, quite simply, wrong. -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
-Original Message- From: Brian May [mailto:bri...@diezorlich.com] Sent: Friday, November 11, 2011 7:12 AM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] 3 phase power snip What is meant by bonded to the ground? Does that mean connecting the nuetral leg of the transformer to the ground? If so, why use the transformer at all when i can just go from a leg to ground? Using the safety ground as a path for the return current instead of using a neutral is not safe because, if the connection between the machine and the safety ground should be loose or fail, then the entire frame of the machine will become electrically hot with respect to the naturally occuring grounded objects nearby. It is also a violation of electrical code and will result in failed safety inspections and rejection of insurance claims if problems are traced to using safety ground as a neutral substitute. Steve Stallings -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
On 11/11/2011 7:11 AM, Brian May wrote: What is meant by bonded to the ground? Does that mean connecting the nuetral leg of the transformer to the ground? If so, why use the transformer at all when i can just go from a leg to ground? If the 3 phase service is fed from a delta connected transformer there may not be a neutral... That was very common in older plants. Now most newer plants use delta-wye transformers so there is a neutral connection at the center of the wye and that point is bonded or connected to ground at the tranformer. At that point a real ground is also established via ground rods. You asked how do more 3 phase machines derive 120 VAC from a 3 phase input, so I was trying to answer that question. If you look at the bus duct systems used in most plants in the US, most of them only have 3 bus bars - no neutral is available. A protective/safety ground wire is assumed. Protective ground connections are always made to machines. Generally the first stop for a protective ground in a power or control cabinet is ground bus bar mounted in the corner of the steel cabinet. And the steel cabinet is normally connected to the machine frame. The protective/safety ground is never used to transmit power. Using it for a power return path is a huge no-no.If you need a neutral, you need to run another wire otherwise you are defeating the purpose of the protective/safety ground. why use the transformer at all when i can just go from a leg to ground? If you think about that statement for a moment; you will realize that you just suggested that you connect the power hot line to the frame of the machine via the load. A very bad idea. Dave -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
On 11/11/2011 9:37 AM, Dave wrote: On 11/11/2011 7:11 AM, Brian May wrote: What is meant by bonded to the ground? Does that mean connecting the nuetral leg of the transformer to the ground? If so, why use the transformer at all when i can just go from a leg to ground? If the 3 phase service is fed from a delta connected transformer there may not be a neutral... That was very common in older plants. Now most newer plants use delta-wye transformers so there is a neutral connection at the center of the wye and that point is bonded or connected to ground at the tranformer. At that point a real ground is also established via ground rods. You asked how do more 3 phase machines derive 120 VAC from a 3 phase input, so I was trying to answer that question. If you look at the bus duct systems used in most plants in the US, most of them only have 3 bus bars - no neutral is available. A protective/safety ground wire is assumed. Protective ground connections are always made to machines. Generally the first stop for a protective ground in a power or control cabinet is ground bus bar mounted in the corner of the steel cabinet. And the steel cabinet is normally connected to the machine frame. The protective/safety ground is never used to transmit power. Using it for a power return path is a huge no-no.If you need a neutral, you need to run another wire otherwise you are defeating the purpose of the protective/safety ground. why use the transformer at all when i can just go from a leg to ground? If you think about that statement for a moment; you will realize that you just suggested that you connect the power hot line to the frame of the machine via the load. A very bad idea. Dave When you put a transformer in a cabinet to create a 120 VAC power source then you have a separately derived system. It is harder to understand why you need to do this, than to just do it. The wiring is very simple. You just need to do it correctly. Here is a web article that points to section 250 in the NEC (National Electric Code) . http://www.mikeholt.com/technical.php?id=grounding/unformatted/Separatesystemstype=utitle=Separately%20Derived%20Systems%20%5BTransformers,%20Generators,%20etc.%5D%20%284-10-2K%29 Even more on neutral to ground bonding.. http://www.iaei.org/magazine/2005/07/grounding-separately-derived-systems/ See the connections between the neutral and the ground on the secondary side of the transformer? It is really that simple. Dave -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
Brian, looking at your questions I get the feeling that you are a bloody beginner as far as power electricity is concerned. I get the scares imagining what you could possibly do to yourself and others, experimenting with your mains supply. It would be much safer for you and would calm my nerves (and apoparently other's, too) if you'd call a local electrician to wire the basic supply of your machinery or what you have. It's worth your life's value. Please get yourself some sound advice! This is not electronics where a fault only results in a burned up transistor or so. To make it clear: grounding is the up and down of electrical power application. Imagine only a little high resistance insulation fault in the primary of your local high voltage transfomer - if the secondary would not be grounded in some way, in this case you could easily experience 10 or 20 kV on your home outlet In case the secondary is ground referenced by connecting the center tap of the secondary windings to ground, this fault might not even be noticed! Floating potentials are a highly dangerous thing, never leave any circuit unreferenced to ground! Peter Blodow Brian May schrieb: Sent from my iPod On Nov 10, 2011, at 10:30 PM, Dave e...@dc9.tzo.com wrote: Usually bigger 3 phase machines being fed with 480 volts or so will only have the 3 phases run to the machine without a neutral wire. The reason being that Line to Neutral on a 480 volt system is 277 volts and that is not very useful for anything other than lighting. To get 120 VAC, two of the phases will be tapped (480 volts) and that will be run to a step down transformer. One the secondary side of the transformer, one leg of the transformer will be declared the hot line, and the other leg will be declared the neutral. The neutral will be bonded to the ground close to the transformer. The hot line is fused.That will establish a proper 120 VAC circuit off the 3 phase input power. What is meant by bonded to the ground? Does that mean connecting the nuetral leg of the transformer to the ground? If so, why use the transformer at all when i can just go from a leg to ground? You could run a separate single phase feed into the existing 3 phase power panel, but then you would have power being fed into one panel from two different sources and that gets tricky from a safety standpoint. I try and avoid doing that whenever possible. Generally when you pull the disconnect switch on a machine panel you want to kill all power in the panel for safety. A lot of machine builders are now avoiding 120 volt power system in their machines entirely. They do that by using DC power supplies that can accept high voltage input power directly. You can buy 3 phase input power supplies that will accept up to 600 VAC and produce 24 VDC. Most of the big power supply makers sell them. Dave On 11/10/2011 10:27 PM, Brian May wrote: Ok that makes sense. Just out of curiosity, How do other machines do it. Our other cnc machines only have the 3 lines and earth ground running into them... Sent from my iPod On Nov 10, 2011, at 9:01 PM, Brian Mihulkabmihu...@hulkster.net wrote: On 11/10/2011 08:50 PM, Brian May wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks Brian Sent from my iPod -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users If its 3 phase 208, one leg to any other leg will give you 208. You have to have the neutral to get 120 from any leg. You should get 120 from any leg to ground but it wouldn't be up to code. Brian -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1
Re: [Emc-users] 3 phase power
Andy, hereabouts, you can't even buy outlets or plugs with only 4 leads. Also, I wouldn't know where to buy a 4 lead power cable. It's 3 or 5. Another thing (but don't tell Brian): in case your motor, 3 phase connected, is wired in wye (star), you have a virtual zero, the common central tap of the windings. If your motor is fairly large, a few kW, you can easily use this for a small single phase supply, say an electronic controller, a work light, a soldering iron or so, without unbalancing the motor. The voltage will depend a little on the momentary load of the motor. I use this when making oscilloscope measurements on VFD's where the 3 phase output is floating and no neutral lead is provided. To test the VFD I only connect a little idling 150 W three phase motor to its output. Peter Blodow andy pugh schrieb: On 11 November 2011 09:25, Peter Blodow p.blo...@dreki.de wrote: In Germany (and most european countries, i think), any electrician installing a three phase supply without neutral and protective earth would be kicked out of business by law for life time instantly. 3P + E outlets are perfectly OK in the UK. As has been hinted at elsewhere in the thread, it depends what the single-phase power is for. If it is to power DC supplies and equipment with internal PSUs like monitors, as long as universal input (120VAC-240VAC) devices are chosen, it should be no problem. -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
On Fri, Nov 11, 2011 at 10:01 AM, Peter Blodow p.blo...@dreki.de wrote: Brian, looking at your questions I get the feeling that you are a bloody beginner as far as power electricity is concerned. I get the scares imagining what you could possibly do to yourself and others, experimenting with your mains supply. It would be much safer for you and would calm my nerves (and apoparently other's, too) if you'd call a local electrician to wire the basic supply of your machinery or what you have. It's worth your life's value. Please get yourself some sound advice! This is not electronics where a fault only results in a burned up transistor or so. I am asking questions to get sound advice. Yes I am a beginner at power electronics. That is why I am asking the question. I am reading what I can and asking different people before I do anything. I am in no hurry and not planning to wire anything until I understand what I am doing. Currently I just have the 3 phase power to the VFD and the rest from an extension cord in the wall. It works, but I would like to improve the design. I have to learn somehow and will probably ask beginner questions So far people have given me further links to read and different things to search on google to understand better. To make it clear: grounding is the up and down of electrical power application. Imagine only a little high resistance insulation fault in the primary of your local high voltage transfomer - if the secondary would not be grounded in some way, in this case you could easily experience 10 or 20 kV on your home outlet In case the secondary is ground referenced by connecting the center tap of the secondary windings to ground, this fault might not even be noticed! Floating potentials are a highly dangerous thing, never leave any circuit unreferenced to ground! Peter Blodow Brian May schrieb: Sent from my iPod On Nov 10, 2011, at 10:30 PM, Dave e...@dc9.tzo.com wrote: Usually bigger 3 phase machines being fed with 480 volts or so will only have the 3 phases run to the machine without a neutral wire. The reason being that Line to Neutral on a 480 volt system is 277 volts and that is not very useful for anything other than lighting. To get 120 VAC, two of the phases will be tapped (480 volts) and that will be run to a step down transformer. One the secondary side of the transformer, one leg of the transformer will be declared the hot line, and the other leg will be declared the neutral. The neutral will be bonded to the ground close to the transformer. The hot line is fused.That will establish a proper 120 VAC circuit off the 3 phase input power. What is meant by bonded to the ground? Does that mean connecting the nuetral leg of the transformer to the ground? If so, why use the transformer at all when i can just go from a leg to ground? You could run a separate single phase feed into the existing 3 phase power panel, but then you would have power being fed into one panel from two different sources and that gets tricky from a safety standpoint. I try and avoid doing that whenever possible. Generally when you pull the disconnect switch on a machine panel you want to kill all power in the panel for safety. A lot of machine builders are now avoiding 120 volt power system in their machines entirely. They do that by using DC power supplies that can accept high voltage input power directly. You can buy 3 phase input power supplies that will accept up to 600 VAC and produce 24 VDC. Most of the big power supply makers sell them. Dave On 11/10/2011 10:27 PM, Brian May wrote: Ok that makes sense. Just out of curiosity, How do other machines do it. Our other cnc machines only have the 3 lines and earth ground running into them... Sent from my iPod On Nov 10, 2011, at 9:01 PM, Brian Mihulkabmihu...@hulkster.net wrote: On 11/10/2011 08:50 PM, Brian May wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks Brian Sent from my iPod -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users If its 3 phase 208, one leg to
Re: [Emc-users] 3 phase power
On 11 November 2011 16:13, Peter Blodow p.blo...@dreki.de wrote: hereabouts, you can't even buy outlets or plugs with only 4 leads. That seems a bit strange. What do you connect the neutral to, if there is no external star point on a motor. for example? A typical VFD, for example, has nowhere to connect that extra wire. Do you leave it dangling? Do you need to fuse it? (To prove they exist: http://www.tlc-direct.co.uk/Main_Index/Plugs_and_Sockets_Industrial_Index/Plugs_and_Sockets_Ind_415v/index.html#Red_415v_16_Amp_4_Pin ) -- atp The idea that there is no such thing as objective truth is, quite simply, wrong. -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
On 11 November 2011 16:22, Brian May bri...@do-precision.com wrote: Yes I am a beginner at power electronics. That is why I am asking the question. I am reading what I can and asking different people before I do anything. I am in no hurry and not planning to wire anything until I understand what I am doing That would be illegal in the UK. Just one of many laws I flout on a regular basis. -- atp The idea that there is no such thing as objective truth is, quite simply, wrong. -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
Brian, power electrics is not a subject to learn by reading a few books. It's a craft. In order to get a licence here in Germany, you have to be an apprentice for three years and a fellow (? Geselle in German) for another few years. After this and only if you have delivered a master piece to the chamber and passed their master's test, you have the chance to get licenced so you are allowed to wire houses and electrical appliances in your own responsibility without supervision, and even so, any house supply must be inspected first by the local supervisiors of the power supply companies before placing in the main fuses into their sockets. Do you think you will get all this knowledge from reading a few books? Even if you get your gadgets running somehow, do you know what gauge wires to use, how large the safety distances from high potential parts have to be, how to measure ground and insulation resistances, which safety switches to use and how to set them correctly, what thermal precautions to take in a crowded power cabinet? From here, I can't give you reading hints because I din't know the US literature. Over here, I would search for text books for professional schools. These schools teach all apprentices aside from their practical work once a week. They give them theoretical and legal information to back up their practical skills with sound knowledge. I remember using such a book when I was in my (US) high school electricity class way back in the sixties. Please don't play with your life and get yourself assistance from a specialist! Peter Blodow Brian May schrieb: Yes I am a beginner at power electronics. That is why I am asking the question. I am reading what I can and asking different people before I do anything. I am in no hurry and not planning to wire anything until I understand what I am doing. Currently I just have the 3 phase power to the VFD and the rest from an extension cord in the wall. It works, but I would like to improve the design. I have to learn somehow and will probably ask beginner questions So far people have given me further links to read and different things to search on google to understand better. To make it clear: grounding is the up and down of electrical power application. Imagine only a little high resistance insulation fault in the primary of your local high voltage transfomer - if the secondary would not be grounded in some way, in this case you could easily experience 10 or 20 kV on your home outlet In case the secondary is ground referenced by connecting the center tap of the secondary windings to ground, this fault might not even be noticed! Floating potentials are a highly dangerous thing, never leave any circuit unreferenced to ground! Peter Blodow -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
On Friday, November 11, 2011 11:28:02 AM Peter Blodow did opine: Brian, looking at your questions I get the feeling that you are a bloody beginner as far as power electricity is concerned. I get the scares imagining what you could possibly do to yourself and others, experimenting with your mains supply. It would be much safer for you and would calm my nerves (and apoparently other's, too) if you'd call a local electrician to wire the basic supply of your machinery or what you have. It's worth your life's value. Please get yourself some sound advice! This is not electronics where a fault only results in a burned up transistor or so. I've been following this thread, debating if I should jump in, but now that Peter has said it, I concur heartily with his advice. Its easy enough to be crispy critter'd around mains power, I've damned near done it to myself at least 3 times in my work around tv stations where we may be the local power companies largest customer. 2nd degree burns on both arms the at the instant bare chest, will take ALL the starch out of you for a few days, and likely lay you up with the shingles for a month or more. Been there, done that, it will totally redefine your personal pain threshold, upwards. No one needs that but somehow I kicked loose and survived. Simply put Brian, if you need to ask these questions, then get a licensed pro who is intimately familiar with the local codes and let him do it. We aren't there and in some cases in this thread are trying to be helpful with inadequate information and almost zero knowledge of local codes. Old buildings with grandfathered in electrical supplies can be legal, and lethal. To make it clear: grounding is the up and down of electrical power application. Imagine only a little high resistance insulation fault in the primary of your local high voltage transfomer - if the secondary would not be grounded in some way, in this case you could easily experience 10 or 20 kV on your home outlet In case the secondary is ground referenced by connecting the center tap of the secondary windings to ground, this fault might not even be noticed! Floating potentials are a highly dangerous thing, never leave any circuit unreferenced to ground! Peter Blodow Brian May schrieb: Sent from my iPod On Nov 10, 2011, at 10:30 PM, Dave e...@dc9.tzo.com wrote: Usually bigger 3 phase machines being fed with 480 volts or so will only have the 3 phases run to the machine without a neutral wire. The reason being that Line to Neutral on a 480 volt system is 277 volts and that is not very useful for anything other than lighting. To get 120 VAC, two of the phases will be tapped (480 volts) and that will be run to a step down transformer. One the secondary side of the transformer, one leg of the transformer will be declared the hot line, and the other leg will be declared the neutral. The neutral will be bonded to the ground close to the transformer. The hot line is fused.That will establish a proper 120 VAC circuit off the 3 phase input power. What is meant by bonded to the ground? Does that mean connecting the nuetral leg of the transformer to the ground? If so, why use the transformer at all when i can just go from a leg to ground? You could run a separate single phase feed into the existing 3 phase power panel, but then you would have power being fed into one panel from two different sources and that gets tricky from a safety standpoint. I try and avoid doing that whenever possible. Generally when you pull the disconnect switch on a machine panel you want to kill all power in the panel for safety. A lot of machine builders are now avoiding 120 volt power system in their machines entirely. They do that by using DC power supplies that can accept high voltage input power directly. You can buy 3 phase input power supplies that will accept up to 600 VAC and produce 24 VDC. Most of the big power supply makers sell them. Dave On 11/10/2011 10:27 PM, Brian May wrote: Ok that makes sense. Just out of curiosity, How do other machines do it. Our other cnc machines only have the 3 lines and earth ground running into them... Sent from my iPod On Nov 10, 2011, at 9:01 PM, Brian Mihulkabmihu...@hulkster.net wrote: On 11/10/2011 08:50 PM, Brian May wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks
Re: [Emc-users] 3 phase power
Yes, you are probably right, I will look for a local professional guy to come and get things going. At least I have an idea of what is happening... Thanks for the advice On Fri, Nov 11, 2011 at 10:54 AM, gene heskett ghesk...@wdtv.com wrote: On Friday, November 11, 2011 11:28:02 AM Peter Blodow did opine: Brian, looking at your questions I get the feeling that you are a bloody beginner as far as power electricity is concerned. I get the scares imagining what you could possibly do to yourself and others, experimenting with your mains supply. It would be much safer for you and would calm my nerves (and apoparently other's, too) if you'd call a local electrician to wire the basic supply of your machinery or what you have. It's worth your life's value. Please get yourself some sound advice! This is not electronics where a fault only results in a burned up transistor or so. I've been following this thread, debating if I should jump in, but now that Peter has said it, I concur heartily with his advice. Its easy enough to be crispy critter'd around mains power, I've damned near done it to myself at least 3 times in my work around tv stations where we may be the local power companies largest customer. 2nd degree burns on both arms the at the instant bare chest, will take ALL the starch out of you for a few days, and likely lay you up with the shingles for a month or more. Been there, done that, it will totally redefine your personal pain threshold, upwards. No one needs that but somehow I kicked loose and survived. Simply put Brian, if you need to ask these questions, then get a licensed pro who is intimately familiar with the local codes and let him do it. We aren't there and in some cases in this thread are trying to be helpful with inadequate information and almost zero knowledge of local codes. Old buildings with grandfathered in electrical supplies can be legal, and lethal. To make it clear: grounding is the up and down of electrical power application. Imagine only a little high resistance insulation fault in the primary of your local high voltage transfomer - if the secondary would not be grounded in some way, in this case you could easily experience 10 or 20 kV on your home outlet In case the secondary is ground referenced by connecting the center tap of the secondary windings to ground, this fault might not even be noticed! Floating potentials are a highly dangerous thing, never leave any circuit unreferenced to ground! Peter Blodow Brian May schrieb: Sent from my iPod On Nov 10, 2011, at 10:30 PM, Dave e...@dc9.tzo.com wrote: Usually bigger 3 phase machines being fed with 480 volts or so will only have the 3 phases run to the machine without a neutral wire. The reason being that Line to Neutral on a 480 volt system is 277 volts and that is not very useful for anything other than lighting. To get 120 VAC, two of the phases will be tapped (480 volts) and that will be run to a step down transformer. One the secondary side of the transformer, one leg of the transformer will be declared the hot line, and the other leg will be declared the neutral. The neutral will be bonded to the ground close to the transformer. The hot line is fused.That will establish a proper 120 VAC circuit off the 3 phase input power. What is meant by bonded to the ground? Does that mean connecting the nuetral leg of the transformer to the ground? If so, why use the transformer at all when i can just go from a leg to ground? You could run a separate single phase feed into the existing 3 phase power panel, but then you would have power being fed into one panel from two different sources and that gets tricky from a safety standpoint. I try and avoid doing that whenever possible. Generally when you pull the disconnect switch on a machine panel you want to kill all power in the panel for safety. A lot of machine builders are now avoiding 120 volt power system in their machines entirely. They do that by using DC power supplies that can accept high voltage input power directly. You can buy 3 phase input power supplies that will accept up to 600 VAC and produce 24 VDC. Most of the big power supply makers sell them. Dave On 11/10/2011 10:27 PM, Brian May wrote: Ok that makes sense. Just out of curiosity, How do other machines do it. Our other cnc machines only have the 3 lines and earth ground running into them... Sent from my iPod On Nov 10, 2011, at 9:01 PM, Brian Mihulkabmihu...@hulkster.net wrote: On 11/10/2011 08:50 PM, Brian May wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and
Re: [Emc-users] 3 phase power
andy pugh schrieb: On 11 November 2011 16:13, Peter Blodow p.blo...@dreki.de wrote: hereabouts, you can't even buy outlets or plugs with only 4 leads. That seems a bit strange. What do you connect the neutral to, if there is no external star point on a motor. for example? When you bolt an outlet to a wall you can't possibly know what the next guy will connect to it later. A typical VFD, for example, has nowhere to connect that extra wire. Do you leave it dangling? Do you need to fuse it? If the VFD (primary side) or any other device has no terminal for the neutral, just leave it. Neutral is never, never, never fused because it would not be selective and mean a danger if devices powered by other circuits are using the same neutral return lead. I killed a lot of LAN power plug adapters some years ago when the neutral wire came loose in the power distribution cabinet. In this case, devices will be connected in series between two phases, and if one is a 2 kW heater and the other a 5 W DC plug, guess which one will get the overvoltage... (To prove they exist: http://www.tlc-direct.co.uk/Main_Index/Plugs_and_Sockets_Industrial_Index/Plugs_and_Sockets_Ind_415v/index.html#Red_415v_16_Amp_4_Pin ) I believe it. In England, there exist also things like haunted castles in the moor, white ghosts at midnight, unremovable blood stains on the carpet and Maggie Thatcher :-)) Look at this: http://de.wikipedia.org/wiki/IEC_60309 for standard industrial outlets and plugs and you will know what I mean. Peter Blodow Peter Bloow -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
Very good idea! And if you want to learn something, this guy will be the right one to ask your questions to. He will know local regulations and hopefuly tell you what is doing, just ask a few holes in his stomach, as we say. Gene, you made some experience the hard way (no envy), which I didn't have in just this manner, but I can remember e few instances where I found myself on the floor, too, without knowing why I laid down... Peter Brian May schrieb: Yes, you are probably right, I will look for a local professional guy to come and get things going. At least I have an idea of what is happening... Thanks for the advice On Fri, Nov 11, 2011 at 10:54 AM, gene heskett ghesk...@wdtv.com wrote: On Friday, November 11, 2011 11:28:02 AM Peter Blodow did opine: Brian, looking at your questions I get the feeling that you are a bloody beginner as far as power electricity is concerned. I get the scares imagining what you could possibly do to yourself and others, experimenting with your mains supply. It would be much safer for you and would calm my nerves (and apoparently other's, too) if you'd call a local electrician to wire the basic supply of your machinery or what you have. It's worth your life's value. Please get yourself some sound advice! This is not electronics where a fault only results in a burned up transistor or so. I've been following this thread, debating if I should jump in, but now that Peter has said it, I concur heartily with his advice. Its easy enough to be crispy critter'd around mains power, I've damned near done it to myself at least 3 times in my work around tv stations where we may be the local power companies largest customer. 2nd degree burns on both arms the at the instant bare chest, will take ALL the starch out of you for a few days, and likely lay you up with the shingles for a month or more. Been there, done that, it will totally redefine your personal pain threshold, upwards. No one needs that but somehow I kicked loose and survived. Simply put Brian, if you need to ask these questions, then get a licensed pro who is intimately familiar with the local codes and let him do it. We aren't there and in some cases in this thread are trying to be helpful with inadequate information and almost zero knowledge of local codes. Old buildings with grandfathered in electrical supplies can be legal, and lethal. To make it clear: grounding is the up and down of electrical power application. Imagine only a little high resistance insulation fault in the primary of your local high voltage transfomer - if the secondary would not be grounded in some way, in this case you could easily experience 10 or 20 kV on your home outlet In case the secondary is ground referenced by connecting the center tap of the secondary windings to ground, this fault might not even be noticed! Floating potentials are a highly dangerous thing, never leave any circuit unreferenced to ground! Peter Blodow Brian May schrieb: Sent from my iPod On Nov 10, 2011, at 10:30 PM, Dave e...@dc9.tzo.com wrote: Usually bigger 3 phase machines being fed with 480 volts or so will only have the 3 phases run to the machine without a neutral wire. The reason being that Line to Neutral on a 480 volt system is 277 volts and that is not very useful for anything other than lighting. To get 120 VAC, two of the phases will be tapped (480 volts) and that will be run to a step down transformer. One the secondary side of the transformer, one leg of the transformer will be declared the hot line, and the other leg will be declared the neutral. The neutral will be bonded to the ground close to the transformer. The hot line is fused.That will establish a proper 120 VAC circuit off the 3 phase input power. What is meant by bonded to the ground? Does that mean connecting the nuetral leg of the transformer to the ground? If so, why use the transformer at all when i can just go from a leg to ground? You could run a separate single phase feed into the existing 3 phase power panel, but then you would have power being fed into one panel from two different sources and that gets tricky from a safety standpoint. I try and avoid doing that whenever possible. Generally when you pull the disconnect switch on a machine panel you want to kill all power in the panel for safety. A lot of machine builders are now avoiding 120 volt power system in their machines entirely. They do that by using DC power supplies that can accept high voltage input power directly. You can buy 3 phase input power supplies that will accept up to 600 VAC and produce 24 VDC. Most of the big power supply makers sell them. Dave On 11/10/2011 10:27 PM, Brian May wrote: Ok that makes sense. Just out of curiosity, How do other machines do it. Our other cnc machines only have the 3 lines and earth ground
Re: [Emc-users] 3 phase power
andy pugh wrote: On 11 November 2011 09:25, Peter Blodow p.blo...@dreki.de wrote: In Germany (and most european countries, i think), any electrician installing a three phase supply without neutral and protective earth would be kicked out of business by law for life time instantly. The US has a VARIETY of 3-phase systems. The 120/208 Wye system is intended for office building and apartment buildings, and you get 208 3-phase for larger loads like elevators and air conditioning, and 120 normal lamps, computers, appliances, etc. A problem is 240 V appliances may not run well on 208. For shops, industrial buildings and such, they often have 120/208 for the office space and 240 Delta for the shop. There are 3 ways to do Delta. There is balanced Delta, where each hot wire has the same voltage to ground. A neutral is not provided by the mains transformer, as it is a fully-floating Delta winding. They provide a small balance transformer, and if it draws any significant current it trips the whole transformer off-line with a ground fault indication. There are two OTHER systems still seen, but generally not installed anymore. There is corner-grounded-delta, where one of the hots is grounded. This gives you 240 V between any of the mains, and is often implemented with only two single phase transformers, so it is often called open delta. One advantage is you get to use residential 2-pole breakers. Another older system that has an extra advantage is center-grounded-delta, where one center-tapped residential transformer is used. This transformer gives you 120/240 V single phase power for office and computer items. A second single phase transformer forms an open delta system, for the 3-phase loads. In this system, no phase wire is neutral, and the system is unbalanced relative to ground. The motors don't care, of course, as long as all the hot-hot voltages are the same. Our building at work has 408 delta, 240 delta, and 120/208 delta, and the breaker panels fill an entire wall of the utility room. (Mostly the 480 breakers, they are really big.) -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
On Friday, November 11, 2011 11:58:11 AM andy pugh did opine: On 11 November 2011 16:22, Brian May bri...@do-precision.com wrote: Yes I am a beginner at power electronics. That is why I am asking the question. I am reading what I can and asking different people before I do anything. I am in no hurry and not planning to wire anything until I understand what I am doing That would be illegal in the UK. Depends on which side of the metering you are on here in the states, Andy. Local municipal/state codes _may_ preempt your doing it yourself, but when I installed a 200 amp service, the puny 1974 style service for the house originally installed became a sub-circuit, I found that the load side of the meter didn't need to be inspected before the new drop was hooked up. So the house wiring, while it has had some additions by me (and the central air installer) is relatively untouched, which simplified the breaker lineup in the 200 amp box quite a bit. Just one of many laws I flout on a regular basis. As have I, but common sense is one I don't flout, at least very often. I can recall that I once had a Phillips double insulated scope hooked across a 10 ohm resistor in the screen circuit of a 4CX5000A in the visual driver side of a GE TF4 transmitter, with a piece of spaghetti over the probe lead as the interlocked door closed on it. That made the scope hot by about 1500 volts so I stood on a plastic stool to operate the scope and take my measurements, which proved that the tube was largely finished, not because of poor cathode emission, but a warped screen grid, it was no longer in the electronic shadow of the control grid and was drawing around 2 amps at sync tip power level while drawing a text book upper end of 18 milliamps as indicated on the screen current meter. I have since learned that you may as well call for a new one if the meter goes above 5 milliamps, the end is nigh on that tube. Sometimes you can tune to increase the loading and keep it running till the new one arrives, mostly you will be down to 75% power in another 2 weeks as that level of peak current draw is pretty self destructive to what is left. Yup, I'm also one of those fools who goes where angels won't. Why, at 77, I am still among us is a puzzle. I don't recommend it for a millisecond. Please, folks, do not use me for an example. :( Cheers, Gene -- There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order. -Ed Howdershelt (Author) My web page: http://coyoteden.dyndns-free.com:85/gene He who despairs over an event is a coward, but he who holds hopes for the human condition is a fool. -- Albert Camus -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
On Friday, November 11, 2011 12:38:29 PM Peter Blodow did opine: Very good idea! And if you want to learn something, this guy will be the right one to ask your questions to. He will know local regulations and hopefuly tell you what is doing, just ask a few holes in his stomach, as we say. Gene, you made some experience the hard way (no envy), which I didn't have in just this manner, but I can remember e few instances where I found myself on the floor, too, without knowing why I laid down... Peter In my case I was already laying on the hot terminals of a 240 volt, 3 phase autoformer trying to reach a small part I had dropped from fatigue as I had been about it then for about 14 hours. To get loose I had to do some fancy kicking with my legs, and my arms flew up, lacerating the backs of both hands on parts above. It was hot and I was extremely sweaty which of course just made that much better a connection. I had 2 choices, I could lay there and let it finish me, or kick to try and get loose, and I actually took a couple of seconds to think about it. I had leaned over it to see if I could retrieve a washer that was part of the shorting arrangement on the back door of the rectifier cabinet of a TF3-AL GE. Which I had to rebuild due to a driver power failure that did not take down the finals high voltage. The operator on duty didn't note it still said 7300 on the meter and was opening doors to see where the problem might be, and of course all hell broke loose when he opened the rectifier cabinet door, the undervoltage trip in the AK2-25 breaker didn't trip it, and he tried to reclose the door. We wound up replacing the finals plate transformer, 4000 lbs of it, and all the primary wire clear to the substation pole, but never did fix the holes burned in a 14 gage steel cabinet, about 4 days off the air all told including an on-site redesign of that undervoltage trip to make it dead reliable. The circuit breaker feeding the autorformer was only a 400 amp breaker. And thanks to grandfathering, the next fuse was a 15 amp in the 7200 volt feed of each phase on the substation pole. There was no entrance breaker in that building, built in about 1956, long before there was an N.E.C. manual. Serviced by 4 pieces of 750 mcm alu. That was the first time it was replaced, but they did a bad crimp and we had to replace it clear into the building when that crimp went to hell about 10 years later. Those fuses have been cleared so many times they won't clear anymore, the holders themselves are so conductive from exploded fuse wire. Last time parts caught fire dripped into the dry grass under the pole had to be stamped out as we never had more than about 1200 gallons of roof runoff water in the cistern. Its still hot, but only because the 509' tower still needs lights. The operator on duty at the time was in the shitter and claimed he saw the lights flicker but had no idea I was the short circuit. It made him feel bad that he wasn't there to help. Since I outweighed that older Vietnam vet by about 100 lbs at the time, I doubt he could have helped much anyway. He was one of my charity cases, no HR dept would ever have hired him, and now gone from the big C with a month to go before he could have filed for early SS. He had brain enough to do the job and actually understood me when I talked technical, but was a physical wreck from Nam wounds, and slowly turning into an alky. I had to chew him out about drinking on the job early on, but did not have a problem again till the last year when it was obvious to all that his time was running out, and that he needed it for pain killer. He had a ball on his back near the spinal cord about the size of a grapefruit, but wouldn't go get it checked out at the local VA hospital because he was also taking care of his long time live in GF whose kidneys had failed and that was, in his mind, more important. I can be a hard ass, but I couldn't fire him as long as the logs were taken care of. I gave him 15 years of employment he likely would not have otherwise had. He had another talent too, he was a relatively busy drummer in Nashville for a while after the V.N. war, backing some of the big names at the time and could still do a damned good job on Jerry Wood's drum set, another story I might tell some time. A walk down memory lane... [overdue snip] Cheers, Gene -- There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order. -Ed Howdershelt (Author) My web page: http://coyoteden.dyndns-free.com:85/gene Engineering meets art in the parking lot and things explode. -- Garry Peterson, about Survival Research Labs -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list
Re: [Emc-users] 3 phase power
On 11/11/2011 03:25 AM, Peter Blodow wrote: Brian, Here in Germany, all electrical supply, home and industry, is done with three phase current plus neutral. For single phase use, like for apartments, the three phases are split up and each apartment or room gets one hot leg plus neutral (plus protective earth). Interesting - you are saying that all homes in Germany have 3phase power? That would mean 3 transformers instead of one - an expensive way to go for the utility company. There is some savings in distribution losses with 3 phase - and in the USA some homes are now getting 3 phase for air-conditioning and a lower rate. The thing that changes this is now inverters have dropped greatly in cost. There is little reason to pay for a 3-phase service install for a one man shop. (Newer Air-conditioners may have an inverter to increase efficiency ) The error of using safety-ground as a neutral is a common error (the most common?) - once current is flowing over the conductor, there is always a voltage drop and then a ground potential is no longer a ground potential. The rule is: Never use safety-ground as a neutral and never use a neutral as a safety-ground. Safety grounds should never have current flowing unless there is something faulty. The number of power connectors around the world is staggering. historically, most countries set up their own standard so some local company would have a cartel to produce the plugs and sockets. Some of the connectors are close enough in size that they will plug into other standards creating dangerous situations. It is also important to note that color codes for power circuits varies by county; sometimes in dangerous ways! I have a bit of this written up at: http://wiki.xtronics.com/index.php/Wire-Gauge_Ampacity#Why_was_.27hot.27_Black_in_House_Wiring.3F There is a second article related to grounding here: http://wiki.xtronics.com/index.php/Lightning_Failures_in_Transducers Karl Schmidt EMail k...@xtronics.com Transtronics, Inc. WEB http://xtronics.com 3209 West 9th Street Ph (785) 841-3089 Lawrence, KS 66049 FAX (785) 841-0434 When angry, count to four; when very angry, swear. -- Mark Twain -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
Hello Karl, the general installation for small houses, like one family buildings or small shops, if made new or repaired, is a 3 phase four lead underground cable, fused with 50 A where it enters the building, coming up from the ground at the edge of the houses wall. In our case, rather typical I think, it's a four times 70 sq. mm alu cable with double PVC insulation. From the main fuses, a four times 25 sq. mm copper cable continues to the current counter. After that, current is fused with three 35 A fuses. Then things split up into three copper strips for the single phase circuits. Each circuit, going to the rooms, is equipped with a 16 A breaker. The tripping characteristics are from very fast (magnetic breaker) for the living rooms, medium for the kitchen and lag for my machinery (mainly thermal breaker). For the welding shop and the outdoor circuits I use 25 A slow blow wire fuses. In our house, being rather large, I have installed 6 sub-distribution cabinets in order to keep the single phase wires and cables at reasonable length. The neutral lead of the incoming ground cable is grounded at the village transformer station together with the center of the secondary windings of the trafo. It's primary is connected in delta so there is no grounding on the high voltage side. Inside the house, lead #4 is connected by a 16 sq. mm copper to the main water pipe, but since the incoming public water supply is now a plastic pipe I doubt that there is much use... After the current measuring device, the neutral is split up into the neutral lead system going to the single phase circuits and the protective ground system, both going throughout the house. This separation must happen as soon the leads become smaller than 10 sq. mm copper, i.e., right before the separation of the single phase circuits. With heavier wires, they may serve both purposes in one. The transformers at the station are three phase transformers, three coils on a three leg iron core. There is only one trafo necessary for one supply line, e.g., one street. This is all a very simple and straightforward system. At the trafo station there is also a circuit breaker to interrupt all phases in case one of them fails, in order to avoid unsymmetrical supply with a danger of burning up three phase motors. A three leg trafo costs about 30% or so more than a single phase trafo, but can carry 70% more energy, which is the reason for this system. Even In little houses and small apartments, all apartments will have a three phase supply because the electric kitchen stoves, usually being the largest consumer, are connected three phase in order to distribute power to the lines, hereby avoiding unsymmetries. These tend to be cancelled out by statistic distribution, looking over a large number of houses. This system is, of course, not so true for old buildings, but after WW II there weren't so many buildings left around in Germany, so we had the chance of new technologies with new installations. When we had bought our house in the seventies, I found remainders of the old installation in the attic: 6 A at 220V AC, single phase. That made it 1300 Watts at maximum, and now I have almost 100 kW available... Peter Blodow Karl Schmidt schrieb: On 11/11/2011 03:25 AM, Peter Blodow wrote: Brian, Here in Germany, all electrical supply, home and industry, is done with three phase current plus neutral. For single phase use, like for apartments, the three phases are split up and each apartment or room gets one hot leg plus neutral (plus protective earth). Interesting - you are saying that all homes in Germany have 3phase power? That would mean 3 transformers instead of one - an expensive way to go for the utility company. There is some savings in distribution losses with 3 phase - and in the USA some homes are now getting 3 phase for air-conditioning and a lower rate. The thing that changes this is now inverters have dropped greatly in cost. There is little reason to pay for a 3-phase service install for a one man shop. (Newer Air-conditioners may have an inverter to increase efficiency ) The error of using safety-ground as a neutral is a common error (the most common?) - once current is flowing over the conductor, there is always a voltage drop and then a ground potential is no longer a ground potential. The rule is: Never use safety-ground as a neutral and never use a neutral as a safety-ground. Safety grounds should never have current flowing unless there is something faulty. The number of power connectors around the world is staggering. historically, most countries set up their own standard so some local company would have a cartel to produce the plugs and sockets. Some of the connectors are close enough in size that they will plug into other standards creating dangerous situations. It is also important to note that color codes for power circuits
Re: [Emc-users] 3 phase power
On Friday, November 11, 2011 05:18:26 PM Peter Blodow did opine: Hello Karl, the general installation for small houses, like one family buildings or small shops, if made new or repaired, is a 3 phase four lead underground cable, fused with 50 A where it enters the building, coming up from the ground at the edge of the houses wall. In our case, rather typical I think, it's a four times 70 sq. mm alu cable with double PVC insulation. From the main fuses, a four times 25 sq. mm copper cable continues to the current counter. After that, current is fused with three 35 A fuses. Then things split up into three copper strips for the single phase circuits. Each circuit, going to the rooms, is equipped with a 16 A breaker. The tripping characteristics are from very fast (magnetic breaker) for the living rooms, medium for the kitchen and lag for my machinery (mainly thermal breaker). For the welding shop and the outdoor circuits I use 25 A slow blow wire fuses. In our house, being rather large, I have installed 6 sub-distribution cabinets in order to keep the single phase wires and cables at reasonable length. The neutral lead of the incoming ground cable is grounded at the village transformer station together with the center of the secondary windings of the trafo. It's primary is connected in delta so there is no grounding on the high voltage side. Inside the house, lead #4 is connected by a 16 sq. mm copper to the main water pipe, but since the incoming public water supply is now a plastic pipe I doubt that there is much use... You need to fix that Peter. I'd take it back to the entrance, drive 2 ground rods adjacent to the foundation that are 2 meters apart, and tie the neutral to both with the same size wire they used for the water pipe connection that is no longer there. Run separate wires to each rod so that it is y'd to each rod at the neutral wire. That will stop 90% of a local lightning strike. After the current measuring device, the neutral is split up into the neutral lead system going to the single phase circuits and the protective ground system, both going throughout the house. This separation must happen as soon the leads become smaller than 10 sq. mm copper, i.e., right before the separation of the single phase circuits. With heavier wires, they may serve both purposes in one. The transformers at the station are three phase transformers, three coils on a three leg iron core. There is only one trafo necessary for one supply line, e.g., one street. This is all a very simple and straightforward system. At the trafo station there is also a circuit breaker to interrupt all phases in case one of them fails, in order to avoid unsymmetrical supply with a danger of burning up three phase motors. A three leg trafo costs about 30% or so more than a single phase trafo, but can carry 70% more energy, which is the reason for this system. Even In little houses and small apartments, all apartments will have a three phase supply because the electric kitchen stoves, usually being the largest consumer, are connected three phase in order to distribute power to the lines, hereby avoiding unsymmetries. These tend to be cancelled out by statistic distribution, looking over a large number of houses. This system is, of course, not so true for old buildings, but after WW II there weren't so many buildings left around in Germany, so we had the chance of new technologies with new installations. When we had bought our house in the seventies, I found remainders of the old installation in the attic: 6 A at 220V AC, single phase. That made it 1300 Watts at maximum, and now I have almost 100 kW available... Compared to my 50.8kw with that 200 amp 254 volt balanced single phase feed, that rather nice. Peter Blodow Karl Schmidt schrieb: On 11/11/2011 03:25 AM, Peter Blodow wrote: Brian, Here in Germany, all electrical supply, home and industry, is done with three phase current plus neutral. For single phase use, like for apartments, the three phases are split up and each apartment or room gets one hot leg plus neutral (plus protective earth). Interesting - you are saying that all homes in Germany have 3phase power? That would mean 3 transformers instead of one - an expensive way to go for the utility company. There is some savings in distribution losses with 3 phase - and in the USA some homes are now getting 3 phase for air-conditioning and a lower rate. The thing that changes this is now inverters have dropped greatly in cost. There is little reason to pay for a 3-phase service install for a one man shop. (Newer Air-conditioners may have an inverter to increase efficiency ) The error of using safety-ground as a neutral is a common error (the most common?) - once current is flowing over the conductor, there is always a voltage drop and then a ground potential is no longer a ground potential. The rule is:
Re: [Emc-users] 3 phase power
On 11/11/2011 11:29 AM, andy pugh wrote: That would be illegal in the UK. Just one of many laws I flout on a regular basis. What would be illegal in the UK? Dave -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
Brian, If you work at some industrial facility or know someone who does, try and find an industrial electrician to help you out. Oftentimes they will not be a licensed electrician as they are not a contractor. They may, or may not have a journeyman's card, depending on their background. You do not want a guy that wires houses even if he is licensed, as he will likely know almost nothing about machine wiring. Dave On 11/11/2011 12:04 PM, Brian May wrote: Yes, you are probably right, I will look for a local professional guy to come and get things going. At least I have an idea of what is happening... Thanks for the advice On Fri, Nov 11, 2011 at 10:54 AM, gene heskettghesk...@wdtv.com wrote: On Friday, November 11, 2011 11:28:02 AM Peter Blodow did opine: Brian, looking at your questions I get the feeling that you are a bloody beginner as far as power electricity is concerned. I get the scares imagining what you could possibly do to yourself and others, experimenting with your mains supply. It would be much safer for you and would calm my nerves (and apoparently other's, too) if you'd call a local electrician to wire the basic supply of your machinery or what you have. It's worth your life's value. Please get yourself some sound advice! This is not electronics where a fault only results in a burned up transistor or so. I've been following this thread, debating if I should jump in, but now that Peter has said it, I concur heartily with his advice. Its easy enough to be crispy critter'd around mains power, I've damned near done it to myself at least 3 times in my work around tv stations where we may be the local power companies largest customer. 2nd degree burns on both arms the at the instant bare chest, will take ALL the starch out of you for a few days, and likely lay you up with the shingles for a month or more. Been there, done that, it will totally redefine your personal pain threshold, upwards. No one needs that but somehow I kicked loose and survived. Simply put Brian, if you need to ask these questions, then get a licensed pro who is intimately familiar with the local codes and let him do it. We aren't there and in some cases in this thread are trying to be helpful with inadequate information and almost zero knowledge of local codes. Old buildings with grandfathered in electrical supplies can be legal, and lethal. To make it clear: grounding is the up and down of electrical power application. Imagine only a little high resistance insulation fault in the primary of your local high voltage transfomer - if the secondary would not be grounded in some way, in this case you could easily experience 10 or 20 kV on your home outlet In case the secondary is ground referenced by connecting the center tap of the secondary windings to ground, this fault might not even be noticed! Floating potentials are a highly dangerous thing, never leave any circuit unreferenced to ground! Peter Blodow Brian May schrieb: Sent from my iPod On Nov 10, 2011, at 10:30 PM, Davee...@dc9.tzo.com wrote: Usually bigger 3 phase machines being fed with 480 volts or so will only have the 3 phases run to the machine without a neutral wire. The reason being that Line to Neutral on a 480 volt system is 277 volts and that is not very useful for anything other than lighting. To get 120 VAC, two of the phases will be tapped (480 volts) and that will be run to a step down transformer. One the secondary side of the transformer, one leg of the transformer will be declared the hot line, and the other leg will be declared the neutral. The neutral will be bonded to the ground close to the transformer. The hot line is fused.That will establish a proper 120 VAC circuit off the 3 phase input power. What is meant by bonded to the ground? Does that mean connecting the nuetral leg of the transformer to the ground? If so, why use the transformer at all when i can just go from a leg to ground? You could run a separate single phase feed into the existing 3 phase power panel, but then you would have power being fed into one panel from two different sources and that gets tricky from a safety standpoint. I try and avoid doing that whenever possible. Generally when you pull the disconnect switch on a machine panel you want to kill all power in the panel for safety. A lot of machine builders are now avoiding 120 volt power system in their machines entirely. They do that by using DC power supplies that can accept high voltage input power directly. You can buy 3 phase input power supplies that will accept up to 600 VAC and produce 24 VDC. Most of the big power supply makers sell them. Dave On 11/10/2011 10:27 PM, Brian May wrote: Ok that makes sense. Just out of curiosity, How do other machines do it. Our other cnc machines only have the 3 lines and
[Emc-users] 3 phase power
This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks Brian Sent from my iPod -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
the lights and most outlets here at work are single phase wired off of 3 phase. On Thu, Nov 10, 2011 at 9:50 PM, Brian May bri...@diezorlich.com wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks Brian Sent from my iPod -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
Yes everything at our shop is wired off 3 phase. But our box has a nuetral. So it goes from leg to nuetral. However my machine only has 4 lines - the 3 legs of power and an earth ground. So i guess my question is do i need the nuetral? Sent from my iPod On Nov 10, 2011, at 8:59 PM, Eric Keller eekel...@psu.edu wrote: the lights and most outlets here at work are single phase wired off of 3 phase. On Thu, Nov 10, 2011 at 9:50 PM, Brian May bri...@diezorlich.com wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks Brian Sent from my iPod -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
On 11/10/2011 06:50 PM, Brian May wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Check the voltage with a meter. Chances are the only voltage you'll find line-to-line is 208V, or possibly 240. You could use a step-down transformer, but it may be cheaper to run another line. There will possibly be 120V between the line and earth, but earth isn't a current-carrying leg and can't be used. Karl -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
On 11/10/2011 08:50 PM, Brian May wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks Brian Sent from my iPod -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users If its 3 phase 208, one leg to any other leg will give you 208. You have to have the neutral to get 120 from any leg. You should get 120 from any leg to ground but it wouldn't be up to code. Brian -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
Ok that makes sense. Just out of curiosity, How do other machines do it. Our other cnc machines only have the 3 lines and earth ground running into them... Sent from my iPod On Nov 10, 2011, at 9:01 PM, Brian Mihulka bmihu...@hulkster.net wrote: On 11/10/2011 08:50 PM, Brian May wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks Brian Sent from my iPod -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users If its 3 phase 208, one leg to any other leg will give you 208. You have to have the neutral to get 120 from any leg. You should get 120 from any leg to ground but it wouldn't be up to code. Brian -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
You need a transformer to step it down,that is how most machines do it. this will be a cleaner set up rather than 3ph and a 1ph line coming in. From: Brian May bri...@diezorlich.com To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Sent: Thursday, November 10, 2011 9:27 PM Subject: Re: [Emc-users] 3 phase power Ok that makes sense. Just out of curiosity, How do other machines do it. Our other cnc machines only have the 3 lines and earth ground running into them... Sent from my iPod On Nov 10, 2011, at 9:01 PM, Brian Mihulka bmihu...@hulkster.net wrote: On 11/10/2011 08:50 PM, Brian May wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks Brian Sent from my iPod -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users If its 3 phase 208, one leg to any other leg will give you 208. You have to have the neutral to get 120 from any leg. You should get 120 from any leg to ground but it wouldn't be up to code. Brian -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] 3 phase power
Usually bigger 3 phase machines being fed with 480 volts or so will only have the 3 phases run to the machine without a neutral wire. The reason being that Line to Neutral on a 480 volt system is 277 volts and that is not very useful for anything other than lighting. To get 120 VAC, two of the phases will be tapped (480 volts) and that will be run to a step down transformer. One the secondary side of the transformer, one leg of the transformer will be declared the hot line, and the other leg will be declared the neutral. The neutral will be bonded to the ground close to the transformer. The hot line is fused.That will establish a proper 120 VAC circuit off the 3 phase input power. You could run a separate single phase feed into the existing 3 phase power panel, but then you would have power being fed into one panel from two different sources and that gets tricky from a safety standpoint. I try and avoid doing that whenever possible. Generally when you pull the disconnect switch on a machine panel you want to kill all power in the panel for safety. A lot of machine builders are now avoiding 120 volt power system in their machines entirely. They do that by using DC power supplies that can accept high voltage input power directly. You can buy 3 phase input power supplies that will accept up to 600 VAC and produce 24 VDC. Most of the big power supply makers sell them. Dave On 11/10/2011 10:27 PM, Brian May wrote: Ok that makes sense. Just out of curiosity, How do other machines do it. Our other cnc machines only have the 3 lines and earth ground running into them... Sent from my iPod On Nov 10, 2011, at 9:01 PM, Brian Mihulkabmihu...@hulkster.net wrote: On 11/10/2011 08:50 PM, Brian May wrote: This is probably an easy question for alot af the people on the list. I have 3 phase power going to my vfd on my machine. I want to the use that same power to power all the 120 single phase components. (the dc power supply for the steppers and varios other motors. ). This way i only need 1 plug I have been reading and people say i can go from 1 leg to a nuetral or leg to leg. I do not have a nuetral line so my question is will it be ok to go from leg to leg for the 120 single phase? Or is there some other component i need? Thanks Brian Sent from my iPod -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users If its 3 phase 208, one leg to any other leg will give you 208. You have to have the neutral to get 120 from any leg. You should get 120 from any leg to ground but it wouldn't be up to code. Brian -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
