pb1592

If a circuit requires a cap rated at 500 volts, is there any way to substitute several caps of a lower voltage in serial/parallel/combination to equal the voltage rating that is required?

For example, I need a 500 volt, 0.1uf (ceramic disc) capacitor but can’t find one… I want to see if I can rig up a few caps that I can get locally at radio shack to fit this circuit, but they do not sell anything above 250volt. I want to know if I could find a combination of lower voltage caps that can be placed in the circuit in such a way as to ‘emulate’ a 500v 0.1uf cap. Any way to do this or do I absolutely have to find a 500v (or higher) cap?

Also, if a circuit calls for a ceramic disc cap does it make any difference, in theory, if an electrolytic of the same rating is used as long as the polarity is correct?

ByLoudDesign

You can series them, but the cap value for each has to be devided by the number used in series. So two(20 .o5 caps @250V in series gives you the same as one (1) .1 cap @ 250V. Chaek out Allied electronics!!!!!
http://www.alliedelec.com/

pb1592

if i understand correctly, what you are suggesting would only work if the caps are paralleled: TWO paralleled 250v, .05mfd caps would be the same as using ONE 250v, .1mfd cap. I'm not exactly sure what would happen if they were added in serial. That, however, does not solve the problem of voltage... I need a way, if possible, to use several caps all with ratings of LESS THAN 250v, placed in a combination such that I can make an equivalent 0.1mfd 500v cap.

I know that capacitance is additive in a parallel circuit, but can the handling of voltage also be increased if the circuit is designed the right way?

what you suggested is additive for capacitance but not for handling a higher voltage.

any ideas? is this even possible?

thanks!

-Brian

fizzwater2

My Feedback: (61)

check out www.digikey.com or www.mouser.com and see if you could order the caps you need - might end up being easier than a bunch of series/parallel combinations in the long run.

Rodney

It makes a big difference in what type of capacitor is being used. If it is an electrolytic, they do not divide voltage well as they are first a resistor (until a voltage potential starts to appear across the plates) and the values are seldom if ever equal resistances. this cause more voltage across the capacitor with the higher initial resistance value and, if this exceeds the rating, will short out and fail. When you must series capacitors to get the required voltage rating, you must parallel each one with a high resistance resistor to force them to equalise the voltage across each one. If using ceramic capacitors or those having air as a dielectric the voltage sharing is less of a problem.

pb1592

Thanks for the info, appreciate it!