RE: Surge filter
How about actually putting some figures into the equation. There have been various answers to the question like Just add a MOV between phases good answers if you only want the circuit to withstand one pulse then the chances are that the MOV would be destroyed and possibly the circuit the MOV put there to protect. If the rise time of the pulse is very fast the MOV will stand no chance of withstanding such a pulse, it needs to have some common mode inductance to damp down the rise time of the pulse to for the MOV to have any chance of clipping the pulse down to a acceptable level. (Best performance use a iron dust ring core in common mode) Secondly by adding two Y capacitance say 10nf from line to earth to the input of the circuit this will again help the pulse be clipped down to a acceptable level. All this circuitry should be placed as close to the input of the mains to help the performance of the filter. Also a filter design program such as Spice, that is if you are in possession of it, does not really help very much as the results given can be sometimes way out to what is actually required, By using the above circuit this will give a better result, probably not a perfect result first time, but it will give you a good starting point. Regards Richard Garbett Approvals Department Research Development Apricot Computers (MEPCD) Ltd. 2500, The Crescent Birmingham Business Park Birmingham B37 7YE -Original Message- From: HMellberg [SMTP:hmellb...@aol.com] Sent: 23 April 1998 17:26 To: k...@scanview.com; emc-p...@ieee.org Subject: Re: Surge filter The best way to design a filter is to establish the performance criteria first. Determine the source impedance Determine the load impedance Determine the attenuation required and at what frequency Determine the roll-off required Now you can determine what order filter you need and whether it is a butterworth or eliptical based on component count and cost. At this point you best use a filter design program such as FILSAP and then characterize it with SPICE. Don't forget that common mode rejection filters are a bit more tricky and require all lines to have a transfer impedance. Last but not least in importance is the topical placement of filters especially critical at high frequency. The closer they are located to the entry/exit point the better the performance. And, return path inductance and length, is not to be ignored. Hans Mellberg Director of Engineering Compliance Certification Services
Recall: Surge filter
Richard Garbett (MPECD) would like to recall the message, Surge filter.
RE: Surge filter
How about actually putting some figures into the equation. There have been various answers to the question like Just add a MOV between phases, good answer if you only want the circuit to withstand one pulse then the chances are that the MOV would be destroyed and possibly the circuit the MOV was protecting. If the rise time of the pulse is very fast the MOV will stand no chance of withstanding such a pulse, it need to have some common mode inductance to damp down the rise time of the pulse -Original Message- From: HMellberg [SMTP:hmellb...@aol.com] Sent: 23 April 1998 17:26 To: k...@scanview.com; emc-p...@ieee.org Subject: Re: Surge filter The best way to design a filter is to establish the performance criteria first. Determine the source impedance Determine the load impedance Determine the attenuation required and at what frequency Determine the roll-off required Now you can determine what order filter you need and whether it is a butterworth or eliptical based on component count and cost. At this point you best use a filter design program such as FILSAP and then characterize it with SPICE. Don't forget that common mode rejection filters are a bit more tricky and require all lines to have a transfer impedance. Last but not least in importance is the topical placement of filters especially critical at high frequency. The closer they are located to the entry/exit point the better the performance. And, return path inductance and length, is not to be ignored. Hans Mellberg Director of Engineering Compliance Certification Services
Re: Surge filter
Dave, Mr Jensen, Dave, your remark about gas discharge tubes would certainly lead to problems in AC mains supplied systems, as upon ignition of the gas, at least a full AC half period will discharge to ground, triggering any diff. mode switches (what their name in US ?) if you are lucky or electrifying your customer if you have bad luck. Better increase clearance or damp out resonances using a 50 Ohm 10 nF series r/caps with Y quality. (10 nF is no leakage current problem !) Regards, Gert Gremmen, == Ce-test, Qualified testing == Consultants in EMC, Electrical safety and Telecommunication Compliance tests for European standards and ce-marking Member of NEC/IEC voting committee for EMC. Our Web presence: http://www.cetest.nl List of current harmonized standards http://www.cetest.nl/emc-harm.htm 15 great tips for the EMC-designer http://www.cetest.nl/features01.htm -Oorspronkelijk bericht- Van: Dave Ried dr...@wgc.woodward.com Aan: EMC Disc Group emc-p...@ieee.org Datum: donderdag 23 april 1998 20:56 Onderwerp: Re: Surge filter Mr. Jenson, The MOV solution will take care of the line-line surge, but don't forget the common mode component of this test. This is usually much more difficult to handle. You are not allowed to use MOVs from line to ground because of leakage (at least in AC systems). The biggest problem is resonance in the common mode filter, if it is a standard topology (CM choke and Y capacitors). This is a very high-Q filter. We have observed nearly 8kV peak line-ground on a 4kV common mode surge voltage because of the resonance. To avoid arcs, this increases primary to ground clearances to unacceptable levels, especially if you are working with low power designs. Again, without any method of clamping (no MOVs) you may be forced into placing a damping network on your filter or possibly a gas discharge tube. good luck Dave Ried dr...@wgc.woodward.com -- From: Ing. Gert Gremmen To: k...@scanview.com; emc-p...@ieee.org Subject: Re: Surge filter Date: Thursday, April 23, 1998 5:09AM Hello Mr jensen Just add a MOV between the phases. A 20 mm disc type will survive both type testing and real life surges. The smaller ones risc failure in testing if that is done according to the proposed test schedules (due to the limited number of pulses they can absorb). 50% reduction of 1 or 2 kV : is that enough ?? The MOV wil limit the pulse to approx 1.7 times it's specified voltage. If you need better performance, use the transient suppressors. They usually limit the voltage to approx 20 % over the indicated value. The lower voltages ones 5-50 Volt up to 50%. If it is for mains applications, select transil value according to peak value of main sinus. Regards, Gert Gremmen, ing. -Oorspronkelijk bericht- Van: k...@scanview.com k...@scanview.com Aan: emc-p...@ieee.org emc-p...@ieee.org Datum: donderdag 23 april 1998 12:51 Onderwerp: Surge filter Dear groupe, Does anyone have some good idears about designing a simple filter for surges (the kind of surges that comes from testing according to IEC 61000-4-5) I was thinking about using an inductor, a capacitor and a MOV. But, what is the requirements for the inductor ? and will it give enough reduction of the puls at all. My experience is that a reduction of 50% is normally enough for our equipment. Best regards, Mr. Kim Boll Jensen ScanView A/S Denmark
Re: Surge filter
The best way to design a filter is to establish the performance criteria first. Determine the source impedance Determine the load impedance Determine the attenuation required and at what frequency Determine the roll-off required Now you can determine what order filter you need and whether it is a butterworth or eliptical based on component count and cost. At this point you best use a filter design program such as FILSAP and then characterize it with SPICE. Don't forget that common mode rejection filters are a bit more tricky and require all lines to have a transfer impedance. Last but not least in importance is the topical placement of filters especially critical at high frequency. The closer they are located to the entry/exit point the better the performance. And, return path inductance and length, is not to be ignored. Hans Mellberg Director of Engineering Compliance Certification Services
Re: Surge filter
Mr. Jenson, The MOV solution will take care of the line-line surge, but don't forget the common mode component of this test. This is usually much more difficult to handle. You are not allowed to use MOVs from line to ground because of leakage (at least in AC systems). The biggest problem is resonance in the common mode filter, if it is a standard topology (CM choke and Y capacitors). This is a very high-Q filter. We have observed nearly 8kV peak line-ground on a 4kV common mode surge voltage because of the resonance. To avoid arcs, this increases primary to ground clearances to unacceptable levels, especially if you are working with low power designs. Again, without any method of clamping (no MOVs) you may be forced into placing a damping network on your filter or possibly a gas discharge tube. good luck Dave Ried dr...@wgc.woodward.com -- From: Ing. Gert Gremmen To: k...@scanview.com; emc-p...@ieee.org Subject: Re: Surge filter List-Post: emc-pstc@listserv.ieee.org Date: Thursday, April 23, 1998 5:09AM Hello Mr jensen Just add a MOV between the phases. A 20 mm disc type will survive both type testing and real life surges. The smaller ones risc failure in testing if that is done according to the proposed test schedules (due to the limited number of pulses they can absorb). 50% reduction of 1 or 2 kV : is that enough ?? The MOV wil limit the pulse to approx 1.7 times it's specified voltage. If you need better performance, use the transient suppressors. They usually limit the voltage to approx 20 % over the indicated value. The lower voltages ones 5-50 Volt up to 50%. If it is for mains applications, select transil value according to peak value of main sinus. Regards, Gert Gremmen, ing. -Oorspronkelijk bericht- Van: k...@scanview.com k...@scanview.com Aan: emc-p...@ieee.org emc-p...@ieee.org Datum: donderdag 23 april 1998 12:51 Onderwerp: Surge filter Dear groupe, Does anyone have some good idears about designing a simple filter for surges (the kind of surges that comes from testing according to IEC 61000-4-5) I was thinking about using an inductor, a capacitor and a MOV. But, what is the requirements for the inductor ? and will it give enough reduction of the puls at all. My experience is that a reduction of 50% is normally enough for our equipment. Best regards, Mr. Kim Boll Jensen ScanView A/S Denmark
Re: Surge filter
Hello Mr jensen Just add a MOV between the phases. A 20 mm disc type will survive both type testing and real life surges. The smaller ones risc failure in testing if that is done according to the proposed test schedules (due to the limited number of pulses they can absorb). 50% reduction of 1 or 2 kV : is that enough ?? The MOV wil limit the pulse to approx 1.7 times it's specified voltage. If you need better performance, use the transient suppressors. They usually limit the voltage to approx 20 % over the indicated value. The lower voltages ones 5-50 Volt up to 50%. If it is for mains applications, select transil value according to peak value of main sinus. Regards, Gert Gremmen, ing. -Oorspronkelijk bericht- Van: k...@scanview.com k...@scanview.com Aan: emc-p...@ieee.org emc-p...@ieee.org Datum: donderdag 23 april 1998 12:51 Onderwerp: Surge filter Dear groupe, Does anyone have some good idears about designing a simple filter for surges (the kind of surges that comes from testing according to IEC 61000-4-5) I was thinking about using an inductor, a capacitor and a MOV. But, what is the requirements for the inductor ? and will it give enough reduction of the puls at all. My experience is that a reduction of 50% is normally enough for our equipment. Best regards, Mr. Kim Boll Jensen ScanView A/S Denmark
Surge filter
Dear groupe, Does anyone have some good idears about designing a simple filter for surges (the kind of surges that comes from testing according to IEC 61000-4-5) I was thinking about using an inductor, a capacitor and a MOV. But, what is the requirements for the inductor ? and will it give enough reduction of the puls at all. My experience is that a reduction of 50% is normally enough for our equipment. Best regards, Mr. Kim Boll Jensen ScanView A/S Denmark
