Capacitors in series and or in parallel

Krankieone · Oct 16, 2020

I am in the process of collecting components to make my RPC easier to use and wire it up in a push button start cabinet with 3ph GPOs located in the appropriate places in the workshop.As part of this project I wanted to do some fine tuning on the balancing capacitors and in the intervening 40 odd years since we covered capacitance in high school I seem to have forgotten how they react in series if I recall correctly in parallel you add the values (50uf + 50uf = 100uf).I would be most grateful if someone would refresh my memory.

rabler · Oct 16, 2020

Series: 1/( (1/C1) + (1/C2))

Fairly straight forward to find via google if my formula isn't clear in simple text.

Phil in Montana · Oct 16, 2020

2- 50uf in series = 25 uf at twice the rated voltage, 2- 50 uf in parallel = 100 uf at rated voltage...Phil

Krankieone · Oct 17, 2020

thankyou that clears it up

9100 · Oct 17, 2020

In series it is a good idea to put resistors on each capacitor to balance the voltage across them. If the leakage of each differs, there will be unequal voltages across them. All you need is enough current to swamp out the leakage, a couple of milliamperes for the oil filled ones you should be using in this application. 50,000 to 100,000 ohms should be adequate.

Bill

Strostkovy · Oct 20, 2020

9100 said:
In series it is a good idea to put resistors on each capacitor to balance the voltage across them. If the leakage of each differs, there will be unequal voltages across them. All you need is enough current to swamp out the leakage, a couple of milliamperes for the oil filled ones you should be using in this application. 50,000 to 100,000 ohms should be adequate.

Bill

If your capacitors are rated to full line voltage it doesn't matter.

The resistor method works fine, but there are nuances to make sure your resistive voltage divider is stronger than your capacitive divider. Especially critical with wide tolerance capacitors or tight voltage margins.

bjr23 · Oct 21, 2020

Phil in Montana said:
2- 50uf in series = 25 uf at twice the rated voltage, 2- 50 uf in parallel = 100 uf at rated voltage...Phil

"rated voltage"?? How do you mean that? bjr

Phil in Montana · Oct 21, 2020

Look on the cap it will state 50uf, 300vdc...rated voltage is 300 volts dc or it might say 25uf 330vac then the rated voltage is 330 volts ac. The rated voltage is a big deal never get close to the rating, the things go up like a hand grenade...Phil

Search

Largest Manufacturing Technology Community on the Web

Search

Capacitors in series and or in parallel

Krankieone

Plastic

rabler

Cast Iron

Phil in Montana

Stainless

Krankieone

Plastic

9100

Diamond

Strostkovy

Titanium

bjr23

Plastic

Phil in Montana

Stainless

Similar threads