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 <[email protected]> Aan: EMC Disc Group <[email protected]> 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 >[email protected] > > ---------- >From: Ing. Gert Gremmen >To: [email protected]; [email protected] >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: [email protected] <[email protected]> >Aan: [email protected] <[email protected]> >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 >> >> >
