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 List-Post: [email protected] 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 > >
