356Views3Replies

# Questions about Capacitors

Does the capacitance stack in a bank? Does the maximum allowed voltage?

How do you wire an SCR? How do I determine what the total output voltage/amps will be?

356Views3Replies

Does the capacitance stack in a bank? Does the maximum allowed voltage?

How do you wire an SCR? How do I determine what the total output voltage/amps will be?

## Discussions

One thing to be aware of is that "identical" valued caps in series may not have the same voltage across each. Caps can have a wide tolerance to their values, on the order of +/-10% being common. When you place caps in series, the highest voltage will be acorss the smallest valued cap.

Just something to keep in mind if you are planning to put them in series to create a bank with an overall greater voltage rating. For example, if you have 2 caps of the same capacitance rated at 100V each, and you place them in series and charge the bank to 200V, you may likely be exceeding the voltage rating of one of the caps. If they were 20% tolerance parts, so that one part was at 120% of its nominal value and the other at 80% of it nominal value, the larger value cap would have 80V across it and the smaller one would have 120 V acorss it.

It's best to allow some margin with the ratings and calculate out the worst case results before you fire up your circuit.

For parallel capacitors Cpar=C1 + C2, but the maximum voltage is that of the least rated capacitor.

For serial capacitors 1/Cser = 1/C1 + 1/C2 and the maximum voltages add up.

Capacitance increases by placing caps in parallel, where

C

_{combined}= C_{1}+ C_{2}+ C_{3}...Google SCR wiring or How to use SCRs