Re: [Emc-users] Crowbars
On 2 October 2013 20:41, Stephen Dubovsky wrote: > Just wire the relay to the AC line. Connect the resistor to the COM & NC > contacts. Relay connects bleeder resistors when AC line is removed. No > need to get fancy. That was what I thought. https://plus.google.com/photos/108164504656404380542/albums/5930254306221907233 Has twice been the result. The problem comes when the relay attempts to open for whatever reason while the caps are not fully discharged. (such as a momentary power glitch) However, there is a similar problem using a solid-state solution, as exactly the same thing will happen if the FET is latched on. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
Just wire the relay to the AC line. Connect the resistor to the COM & NC contacts. Relay connects bleeder resistors when AC line is removed. No need to get fancy. Stephen On Wed, Oct 2, 2013 at 2:43 PM, Dave Cole wrote: > That could work as well. > > I thought this was part of your safety circuit to bring the power supply > voltage down to zero ASAP. As in "the motor is running away and I need > to kill the drive". > > Dave > > > > On 10/2/2013 1:11 PM, andy pugh wrote: > > On 2 October 2013 17:33, Dave Cole wrote: > > > >> When the power drops out the contactor drops out and will > >> not pull back in when the power recovers unless you push the "power on" > >> button. > > I think I am happy to trust this to HAL. I may add an input to HAL > > from the contactor "discharging mode active" and interlock that to the > > DC bus voltage so that I can't re-energise the PSU until the caps are > > down below a few volts. > > > > (There is a separate LinuxCNC-controlled contactor that powers up all > > the AC loads, servo PSU, VFD, Ikea LED lights…) > > > > > -- > October Webinars: Code for Performance > Free Intel webinars can help you accelerate application performance. > Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most > from > the latest Intel processors and coprocessors. See abstracts and register > > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
That could work as well. I thought this was part of your safety circuit to bring the power supply voltage down to zero ASAP. As in "the motor is running away and I need to kill the drive". Dave On 10/2/2013 1:11 PM, andy pugh wrote: > On 2 October 2013 17:33, Dave Cole wrote: > >> When the power drops out the contactor drops out and will >> not pull back in when the power recovers unless you push the "power on" >> button. > I think I am happy to trust this to HAL. I may add an input to HAL > from the contactor "discharging mode active" and interlock that to the > DC bus voltage so that I can't re-energise the PSU until the caps are > down below a few volts. > > (There is a separate LinuxCNC-controlled contactor that powers up all > the AC loads, servo PSU, VFD, Ikea LED lights…) > -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
On Wed, Oct 2, 2013, at 01:58 PM, andy pugh wrote: > On 2 October 2013 18:28, Jon Elson wrote: > > > or use a FET to control the dump resistor. > > I would like to do this, but I am not sure how to wire a FET to > discharge the cap when AC power is removed (Whereas an NC relay does > this easily) One way to use a FET (or IGBT) for this: Put a 12 to 15V zener diode from gate to source. Put a resistor from gate to drain. The resistor should be chosen to deliver 10-20mA. For 300V, that means 15-30K. It will dissipate 3-6 watts, so size it conservatively. Connect a low power relay such that when power is on it shorts the gate to the source, turning the FET off. When the power goes off, the relay opens, and the 10mA current charges the gate until the zener clamps it. That turns the FET on. Once the bus discharges below 12V the gate voltage will droop, but at that point you don't care. Note that just like the relay, the FET can fail in the ON position, applying steady state power to your bleeder resistor. In one project I worked on, we used the water heater elements and mounted a small bi-metal snap-disk thermostat to the element. If the element overheats because of continuous power, the thermostat opens and kills main power by turning off the main contactor. -- John Kasunich jmkasun...@fastmail.fm -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
On 2 October 2013 18:28, Jon Elson wrote: > If this is the case, the contacts will still be welded, so open up the > relay and examine it. I will, but as I still have the welded relay from last time, I think I know that it can happen. > Normal relays are severely derated for DC, and breaking 300 V > DC cannot be accomplished by any standard relay. It probably doesn't take > a glitch on the mains, just after so many on/off cycles, you will get a > failure as the contacts degrade. The relay should never even try to _break_ 300V DC. It _makes_ 300V DC to discharge the caps, but should only ever break when the caps are at 0V. > or use a FET to control the dump resistor. I would like to do this, but I am not sure how to wire a FET to discharge the cap when AC power is removed (Whereas an NC relay does this easily) I though of using the fact that Thyristors latch on when current is flowing, but then I think I run the risk of restoring AC power while the device is still conducting, with the same result. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
andy pugh wrote: > I think that the failure mode is that, in the case of a power glitch, > the crowbar relay switches and is discharging 300V DC at a fair > current, then the power returns and the NC contact tries to break 300V > 10A and welds the NC contacts closed. Then the NO contacts close and > we now have the crowbar resistor connected directly across the > rectifier output. The crowbar resistor is not sized for continuous > operation. > If this is the case, the contacts will still be welded, so open up the relay and examine it. Normal relays are severely derated for DC, and breaking 300 V DC cannot be accomplished by any standard relay. It probably doesn't take a glitch on the mains, just after so many on/off cycles, you will get a failure as the contacts degrade. One way to solve the fire problem is to put a fuse (correctly rated for 300 V DC) in series with the source, and strap it to the resistor. When the resistor overheats, it will melt the fuse. But, that will be a safety hack, rather than a fix. Use double-break contactors with large contact spacing for 600 V+, or use a FET to control the dump resistor. Jon -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
On 2 October 2013 17:33, Dave Cole wrote: > When the power drops out the contactor drops out and will > not pull back in when the power recovers unless you push the "power on" > button. I think I am happy to trust this to HAL. I may add an input to HAL from the contactor "discharging mode active" and interlock that to the DC bus voltage so that I can't re-energise the PSU until the caps are down below a few volts. (There is a separate LinuxCNC-controlled contactor that powers up all the AC loads, servo PSU, VFD, Ikea LED lights…) -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
Andy, I think you need to add a sealed in relay on your input power contactor circuit. You start the machine by pushing a power on button which has a seal in contact to hold the contactor in place after the button is released. When the power drops out the contactor drops out and will not pull back in when the power recovers unless you push the "power on" button.To make it even safer, you can add an auxiliary contact off the crowbar relay such that if the crowbar relay is stuck on, the start circuit will not function ( a NC axillary contact off the crowbar contactor should work). I'd stick all of this into a metal box just in case something catches on fire.. the box should contain the flames. Contactors are typically much more robust than relays. Regarding DC vs AC contactors, I would use a regular AC contactor for the crowbar contactor. DC contactors are specialized in that they can break DC current which is difficult to do. You don't need to break DC current, you need to conduct DC current.. a different problem that should cause little to no arcing.Just interlock the crowbar contactor with the infeed contactor so that if the crowbar contactor fails stuck on, you don't drive power supply current into the resistor. Over here (in the USA) we have cheap Fuji contactors available from Automation Direct. I'd find out who sells them in the UK.A 25 amp IEC contactor with a 24 vdc coil is about $40.00 US. http://www.automationdirect.com/adc/Shopping/Catalog/Motor_Controls/Fuji_Contactors_-z-_Overloads/9_to_25_Amp I have used hundreds of them and they seem to be very durable. It looks like http://www.lamonde.com/ sells Automation Direct equipment in the UK but I don't see Fuji Contactors in the list of items sold. Dave On 10/2/2013 5:54 AM, andy pugh wrote: > The PSU on my milling machine blew up again last night. This is the > second time it has happened. I haven't pulled the box out of the > machine yet, but I expect to see this again: > https://picasaweb.google.com/lh/photo/xxfP_tT7Ae0op6GxUhSDvtMTjNZETYmyPJy0liipFm0?feat=directlink > Which is a power resistor that has got so hot that it has exploded. > (quite an odd failure mode for a resistor). > > The PSU is home-made and consists mainly of a bunch of capacitors and > rectifier. > > Also in the box are two relays, two power resistors and a timer > circuit. One resistor is a soft-start on the AC input side. When power > is first applied the power passes through one of the resistors to > limit the surge current, and then the timer closes a relay that > short-out that resistor. I am fairly happy that that part of the > circuit is reliable. > > A second relay is used in change-over mode. This has a 240V coil > connected to the incoming power. When the PSU is powered up the relay > closes, and supplies power to everything else inside, when the power > goes off the relay opens and the NC contacts connect a crowbar > resistor across the capacitors to discharge them. > > I think that the failure mode is that, in the case of a power glitch, > the crowbar relay switches and is discharging 300V DC at a fair > current, then the power returns and the NC contact tries to break 300V > 10A and welds the NC contacts closed. Then the NO contacts close and > we now have the crowbar resistor connected directly across the > rectifier output. The crowbar resistor is not sized for continuous > operation. > > I think that there are two problems here. If the crowbar contacts on > the relay are welded shut then the power contacts should not be able > to close. I think I need a more explicitly interlocked relay. > Currently I am using: JG64U here: > http://www.maplin.co.uk/round-base-10a-relays-2567 > > I think that the term I need to search for is "force guided" but would > like some confirmation that that means what I think it means. Are > "contactors" more dependable in this sense? > > The real problem is that the relay is not capable of breaking 300VDC. > However, DC rated contactors are pretty expensive, and seem to jump > for 220 to 44 and then 690V. I don't think I have room in the box for > the big ones. I wonder if > http://uk.rs-online.com/web/p/contactors/4111687/ would be OK? It > really should never try to break with the capacitors charged > (interlocked in HAL, which can see the DC bus voltage, and with the > crowbar in circuit the voltage will drop pretty quickly anyway) > > My inclination is to look for a solid-state solution, but solid-state > isn't very good at doing anything at all on the basis of the power > going off > > -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=6013
Re: [Emc-users] Crowbars
Quoth John Kasunich. > >$13 gets the same ohms and watts, but can run continuously if needed: >http://www.ebay.com/itm/131001379245 That's brilliant... stick a kettle on top and Andy automatically gets a nice cuppa when he's finished making chips :-) -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
On Wed, Oct 2, 2013, at 10:47 AM, andy pugh wrote: > I guess I could use a 250W resistor, which is 30s to 5V, or a 1kW > resistor, which is 7.5 seconds to 5V. But both seem wasteful, and I am > not sure I have the space. > (Also quite expensive: > http://uk.rs-online.com/web/p/panel-mount-fixed-resistors/7014059/ ) For intermittent duty (as you are using it - connected only on power down), the cheapest high-power resistors are heaters. For example: $8 gets you 38.4 ohms, 1500W intermittent (or continuous, if wet ;-): http://www.ebay.com/itm/200960173435 That has more then enough thermal mass to handle 20,000uF at 300V. I've used 2 of those in series to discharge 24,000uF at 600V (4.8 times the energy). The flange makes it fairly easy to mount. $13 gets the same ohms and watts, but can run continuously if needed: http://www.ebay.com/itm/131001379245 Just don't put anything meltable nearby. I've seen these used as DB resistors for spindle drives - mounted in a mesh box on top of the machine so the heat can escape. -- John Kasunich jmkasun...@fastmail.fm -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
On 2 October 2013 16:00, jrmitchellj . wrote: > Large in value sense. The problem here is that my capacitors are large (in both senses) and so a large value resistor will take a long time to discharge the caps. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
Large in value sense. --J. Ray Mitchell Jr. jrmitche...@gmail.com (818)324-7573 “Truth is treason in the Empire of Lies.” — Ron Paul On Wed, Oct 2, 2013 at 7:47 AM, andy pugh wrote: > On 2 October 2013 14:55, jrmitchellj . wrote: > > The relay or contactor you use must be a "break before make" style > > The ones I have been using are meant to be, but they are not > force-guided to ensure it. > > > A larger value resistor for bleed off might be in order. > > I usually put a very large value resistor across the power supply. You > > waste some power, but you always know the supply has been bled off before > > poking into it. > > Do you mean "very large" in the physical sense or the value sense? > > I have 20,000uF of caps at 300V. For a 100W resistor to be happy > steady-state then the minimum resistance it can have is about 1k. > That will take 82 seconds to drop the voltage to 5V, which is longer > than I would like. > > I guess I could use a 250W resistor, which is 30s to 5V, or a 1kW > resistor, which is 7.5 seconds to 5V. But both seem wasteful, and I am > not sure I have the space. > (Also quite expensive: > http://uk.rs-online.com/web/p/panel-mount-fixed-resistors/7014059/ ) > > Currently the 50R 100W resistor which is switched-in only when needed > takes 5 seconds to drop the voltage to comfortable levels. And it > doesn't even get warm in that time. (unless, as has been discovered, > the relay that switches it in manages to weld shut and keep it in > circuit at the same time as the mains supply is connected) > > -- > atp > If you can't fix it, you don't own it. > http://www.ifixit.com/Manifesto > > > -- > October Webinars: Code for Performance > Free Intel webinars can help you accelerate application performance. > Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most > from > the latest Intel processors and coprocessors. See abstracts and register > > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
On 2 October 2013 14:55, jrmitchellj . wrote: > The relay or contactor you use must be a "break before make" style The ones I have been using are meant to be, but they are not force-guided to ensure it. > A larger value resistor for bleed off might be in order. > I usually put a very large value resistor across the power supply. You > waste some power, but you always know the supply has been bled off before > poking into it. Do you mean "very large" in the physical sense or the value sense? I have 20,000uF of caps at 300V. For a 100W resistor to be happy steady-state then the minimum resistance it can have is about 1k. That will take 82 seconds to drop the voltage to 5V, which is longer than I would like. I guess I could use a 250W resistor, which is 30s to 5V, or a 1kW resistor, which is 7.5 seconds to 5V. But both seem wasteful, and I am not sure I have the space. (Also quite expensive: http://uk.rs-online.com/web/p/panel-mount-fixed-resistors/7014059/ ) Currently the 50R 100W resistor which is switched-in only when needed takes 5 seconds to drop the voltage to comfortable levels. And it doesn't even get warm in that time. (unless, as has been discovered, the relay that switches it in manages to weld shut and keep it in circuit at the same time as the mains supply is connected) -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
Contactors are generally a lot more robust than relays. Since switching to contactors on my supplies I have never had any welded contact issues. I normally switch the AC before the rectifier instead of the DC. This does mean the smoothing caps are permanently connected to the load but in my opinion this is a good thing for two reasons. First the caps help absorb the reverse energy dump from stopping the motors quickly. Secondly in my experience having the DC bus live for a fraction of a second after ESTOP helps stop motion quickly. Instead of simply letting the motors free wheel the drives will actively try to stop motion until the supply dies. Les On 02/10/2013 10:54, andy pugh wrote: > The PSU on my milling machine blew up again last night. This is the > second time it has happened. I haven't pulled the box out of the > machine yet, but I expect to see this again: > https://picasaweb.google.com/lh/photo/xxfP_tT7Ae0op6GxUhSDvtMTjNZETYmyPJy0liipFm0?feat=directlink > Which is a power resistor that has got so hot that it has exploded. > (quite an odd failure mode for a resistor). > > The PSU is home-made and consists mainly of a bunch of capacitors and > rectifier. > > Also in the box are two relays, two power resistors and a timer > circuit. One resistor is a soft-start on the AC input side. When power > is first applied the power passes through one of the resistors to > limit the surge current, and then the timer closes a relay that > short-out that resistor. I am fairly happy that that part of the > circuit is reliable. > > A second relay is used in change-over mode. This has a 240V coil > connected to the incoming power. When the PSU is powered up the relay > closes, and supplies power to everything else inside, when the power > goes off the relay opens and the NC contacts connect a crowbar > resistor across the capacitors to discharge them. > > I think that the failure mode is that, in the case of a power glitch, > the crowbar relay switches and is discharging 300V DC at a fair > current, then the power returns and the NC contact tries to break 300V > 10A and welds the NC contacts closed. Then the NO contacts close and > we now have the crowbar resistor connected directly across the > rectifier output. The crowbar resistor is not sized for continuous > operation. > > I think that there are two problems here. If the crowbar contacts on > the relay are welded shut then the power contacts should not be able > to close. I think I need a more explicitly interlocked relay. > Currently I am using: JG64U here: > http://www.maplin.co.uk/round-base-10a-relays-2567 > > I think that the term I need to search for is "force guided" but would > like some confirmation that that means what I think it means. Are > "contactors" more dependable in this sense? > > The real problem is that the relay is not capable of breaking 300VDC. > However, DC rated contactors are pretty expensive, and seem to jump > for 220 to 44 and then 690V. I don't think I have room in the box for > the big ones. I wonder if > http://uk.rs-online.com/web/p/contactors/4111687/ would be OK? It > really should never try to break with the capacitors charged > (interlocked in HAL, which can see the DC bus voltage, and with the > crowbar in circuit the voltage will drop pretty quickly anyway) > > My inclination is to look for a solid-state solution, but solid-state > isn't very good at doing anything at all on the basis of the power > going off > > -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
The relay or contactor you use must be a "break before make" style. I like contactors better as the distance between contacts tends to be larger, so more time between break & make. A larger value resistor for bleed off might be in order. I usually put a very large value resistor across the power supply. You waste some power, but you always know the supply has been bled off before poking into it. --J. Ray Mitchell Jr. jrmitche...@gmail.com (818)324-7573 “Truth is treason in the Empire of Lies.” — Ron Paul On Wed, Oct 2, 2013 at 6:12 AM, andy pugh wrote: > On 2 October 2013 13:54, John Kasunich wrote: > > Various companies make contactors intended for DC drives. > > Ah, yes, that looks approximately perfect apart from the cost and the > delivery time. (I can't see any on eBay UK) > > I have ordered the 220VDC rated contactor from RS, however, as I > wanted a quick solution. > > -- > atp > If you can't fix it, you don't own it. > http://www.ifixit.com/Manifesto > > > -- > October Webinars: Code for Performance > Free Intel webinars can help you accelerate application performance. > Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most > from > the latest Intel processors and coprocessors. See abstracts and register > > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
On 2 October 2013 13:54, John Kasunich wrote: > Various companies make contactors intended for DC drives. Ah, yes, that looks approximately perfect apart from the cost and the delivery time. (I can't see any on eBay UK) I have ordered the 220VDC rated contactor from RS, however, as I wanted a quick solution. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
Various companies make contactors intended for DC drives. They have a conventional three-pole frame, but the center pole has NC contacts (the two outer poles have conventional NO contacts). The center pole is intended to apply a DB resistor across the motor armature after the outer poles disconnect the motor from the drive output. By design, it is impossible for the NO and NC contacts to be closed at the same time. Asea makes a whole family of them, called the EFLG series. They have permanant magnet arc blow-outs on the NC pole (hence the polarity markings on the contactor below) http://www.ebay.com/itm/230905835584 That one is from the US ebay and has a 120V coil, you might have better luck finding a 230V coil on ebay.uk. http://www.ebay.com/itm/390624331282 is another one, the coil voltage isn't specified in the auction but the full part number is, you could google for details. On Wed, Oct 2, 2013, at 08:21 AM, andy pugh wrote: > On 2 October 2013 11:09, john d norton wrote: > > Maybe look into using a starter solinoid maybe 12 or 24 v I know > > It really needs to have interlocked NO / NC contacts and be controlled by > 240V. > > -- > atp > If you can't fix it, you don't own it. > http://www.ifixit.com/Manifesto > > -- > October Webinars: Code for Performance > Free Intel webinars can help you accelerate application performance. > Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from > the latest Intel processors and coprocessors. See abstracts and register > > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users -- John Kasunich jmkasun...@fastmail.fm -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
On 2 October 2013 11:09, john d norton wrote: > Maybe look into using a starter solinoid maybe 12 or 24 v I know It really needs to have interlocked NO / NC contacts and be controlled by 240V. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Crowbars
Maybe look into using a starter solinoid maybe 12 or 24 v I know but should handle a fair amount of current failing that could you use all three phase contacts of a three phase contactor or even four contacts if you get the spare as n/o John d norton C/o John Norton Fabs Ltd > On 2 Oct 2013, at 10:54, andy pugh wrote: > > The PSU on my milling machine blew up again last night. This is the > second time it has happened. I haven't pulled the box out of the > machine yet, but I expect to see this again: > https://picasaweb.google.com/lh/photo/xxfP_tT7Ae0op6GxUhSDvtMTjNZETYmyPJy0liipFm0?feat=directlink > Which is a power resistor that has got so hot that it has exploded. > (quite an odd failure mode for a resistor). > > The PSU is home-made and consists mainly of a bunch of capacitors and > rectifier. > > Also in the box are two relays, two power resistors and a timer > circuit. One resistor is a soft-start on the AC input side. When power > is first applied the power passes through one of the resistors to > limit the surge current, and then the timer closes a relay that > short-out that resistor. I am fairly happy that that part of the > circuit is reliable. > > A second relay is used in change-over mode. This has a 240V coil > connected to the incoming power. When the PSU is powered up the relay > closes, and supplies power to everything else inside, when the power > goes off the relay opens and the NC contacts connect a crowbar > resistor across the capacitors to discharge them. > > I think that the failure mode is that, in the case of a power glitch, > the crowbar relay switches and is discharging 300V DC at a fair > current, then the power returns and the NC contact tries to break 300V > 10A and welds the NC contacts closed. Then the NO contacts close and > we now have the crowbar resistor connected directly across the > rectifier output. The crowbar resistor is not sized for continuous > operation. > > I think that there are two problems here. If the crowbar contacts on > the relay are welded shut then the power contacts should not be able > to close. I think I need a more explicitly interlocked relay. > Currently I am using: JG64U here: > http://www.maplin.co.uk/round-base-10a-relays-2567 > > I think that the term I need to search for is "force guided" but would > like some confirmation that that means what I think it means. Are > "contactors" more dependable in this sense? > > The real problem is that the relay is not capable of breaking 300VDC. > However, DC rated contactors are pretty expensive, and seem to jump > for 220 to 44 and then 690V. I don't think I have room in the box for > the big ones. I wonder if > http://uk.rs-online.com/web/p/contactors/4111687/ would be OK? It > really should never try to break with the capacitors charged > (interlocked in HAL, which can see the DC bus voltage, and with the > crowbar in circuit the voltage will drop pretty quickly anyway) > > My inclination is to look for a solid-state solution, but solid-state > isn't very good at doing anything at all on the basis of the power > going off > > > -- > atp > If you can't fix it, you don't own it. > http://www.ifixit.com/Manifesto > > -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
[Emc-users] Crowbars
The PSU on my milling machine blew up again last night. This is the second time it has happened. I haven't pulled the box out of the machine yet, but I expect to see this again: https://picasaweb.google.com/lh/photo/xxfP_tT7Ae0op6GxUhSDvtMTjNZETYmyPJy0liipFm0?feat=directlink Which is a power resistor that has got so hot that it has exploded. (quite an odd failure mode for a resistor). The PSU is home-made and consists mainly of a bunch of capacitors and rectifier. Also in the box are two relays, two power resistors and a timer circuit. One resistor is a soft-start on the AC input side. When power is first applied the power passes through one of the resistors to limit the surge current, and then the timer closes a relay that short-out that resistor. I am fairly happy that that part of the circuit is reliable. A second relay is used in change-over mode. This has a 240V coil connected to the incoming power. When the PSU is powered up the relay closes, and supplies power to everything else inside, when the power goes off the relay opens and the NC contacts connect a crowbar resistor across the capacitors to discharge them. I think that the failure mode is that, in the case of a power glitch, the crowbar relay switches and is discharging 300V DC at a fair current, then the power returns and the NC contact tries to break 300V 10A and welds the NC contacts closed. Then the NO contacts close and we now have the crowbar resistor connected directly across the rectifier output. The crowbar resistor is not sized for continuous operation. I think that there are two problems here. If the crowbar contacts on the relay are welded shut then the power contacts should not be able to close. I think I need a more explicitly interlocked relay. Currently I am using: JG64U here: http://www.maplin.co.uk/round-base-10a-relays-2567 I think that the term I need to search for is "force guided" but would like some confirmation that that means what I think it means. Are "contactors" more dependable in this sense? The real problem is that the relay is not capable of breaking 300VDC. However, DC rated contactors are pretty expensive, and seem to jump for 220 to 44 and then 690V. I don't think I have room in the box for the big ones. I wonder if http://uk.rs-online.com/web/p/contactors/4111687/ would be OK? It really should never try to break with the capacitors charged (interlocked in HAL, which can see the DC bus voltage, and with the crowbar in circuit the voltage will drop pretty quickly anyway) My inclination is to look for a solid-state solution, but solid-state isn't very good at doing anything at all on the basis of the power going off -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
