I need your help with capacitors...

I'm restoring a 160A inverter welding machine, model Fimer X164. One of the capacitors has cracked and I need tochange that..

Information about the capacitor on the board (i.e. exploded):

PILKOR 10nF 300V-Y2 PCY2 130 MKP

I can't find an identical capacitor but find similar values.

I have

1- 10 n K 400 RIFA 404 FVN

2- RIFA 271 Y 522 250V MP

Can I use capacitor 1? Or what do you suggest as a replacement for this capacitor?

enter image description here

  • \$\begingroup\$ what circuit currents do you expect? \$\endgroup\$ Commented Dec 6, 2016 at 0:54
  • \$\begingroup\$ What AC supply voltage does this machine use? \$\endgroup\$ Commented Dec 6, 2016 at 2:21
  • \$\begingroup\$ @TonyStewart.EEsince'75 Welding Machine works with 220V - value of old and exploded capacitor is 300V.. \$\endgroup\$
    – byzskl01
    Commented Dec 6, 2016 at 4:44
  • \$\begingroup\$ @ThreePhaseEel Machine works with 220 V \$\endgroup\$
    – byzskl01
    Commented Dec 6, 2016 at 4:44
  • \$\begingroup\$ The second isn't 10nF, but 270. \$\endgroup\$
    – Antonio
    Commented Dec 6, 2016 at 9:28

1 Answer 1


Don't gamble your life over saving a couple of bucks!

The capacitor that exploded was not any old capacitor -- it is a special "Class Y" capacitor that's designed not to ever fail as a short circuit, which is extremely important because Class Y capacitors are used between things at mains voltage (no touchy!) and things you can touch. If a regular capacitor like Capacitor 1 was used instead, it could short out when it failed, causing your welder to turn into a people-zapper. Capacitor 2 appears to be of the correct type (Class Y) and voltage rating, but of the wrong value (270pF?) and probably won't be as effective at its job as the exploded capacitor was.

Get a 10nF, 250VAC Y2 capacitor from a reputable distributor (DigiKey, Mouser, Newark/Farnell, TME, RS/Allied, Future, and Arrow are the ones I know of -- it will not be China-cheap, but penny-wise is pound-foolish with life-safety-critical components like these) and install it in place of the blown-up cap. (One way to determine if something's a proper safety rated capacitor is to look for test lab marks, such as UL, CSA, or the VDE mark seen on Capacitor 2 in your picture.)

  • \$\begingroup\$ Thank you very much for that important informations.. I dont think change capacitor before ask this place.. I should change only Y type? Or Can it be X type? And last question: Old capacitor is 300V.. Can I use 250V or over 300V? Thank you a lot of... \$\endgroup\$
    – byzskl01
    Commented Dec 6, 2016 at 13:01
  • 1
    \$\begingroup\$ You must match the Y-rating. Some caps are rated for both X and Y applications, which is fine, but your replacement still must meet Y2. \$\endgroup\$ Commented Dec 6, 2016 at 13:35
  • \$\begingroup\$ You need a Y2 or Y1 capacitor (some caps are dual rated X1Y1 or X1Y2, they are fine. Just don't get anything that's say X1 or X2 without the Y). Also, 250VAC Y capacitors are fine in a 220VAC appliance -- X/Y capacitors are rated by their nominal working voltage. \$\endgroup\$ Commented Dec 6, 2016 at 23:10
  • \$\begingroup\$ @ThreePhaseEel Thank you very much dear.. They're very important info's.. Sorry for lot of questions but, I can't find 10nF.. Can I use 22nF for this application? (Inverter Welding Machine 220V) \$\endgroup\$
    – byzskl01
    Commented Dec 8, 2016 at 12:06
  • \$\begingroup\$ @byzskl01 two 22nF in series will do in a pinch \$\endgroup\$ Commented Dec 8, 2016 at 12:36

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