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Re: [TCML] PFC Cap Bank


I use standard 10 amp toggle switches. Lets assume that 30% of the current is flowing through the PFC bank. That would be about 7.5 amps. If that current is now divided between 3 capacitors (100 + 100 + 50 for example) in parallel, then each capacitor only has to handle 7.5/3 = 2.5 amps. With one switch per capacitor, that is easily handled by a standard 10 amp toggle switch. Even when you only have one capacitor switched in, it will only have 7.5 amps flowing through it. If you really want to be conservative just take a 10 amp DPST switch and wire the 2 poles in parallel to make a 20 amp toggle switch.

I assume that you also want a master switch to enable/disable PFC. Even though a 10 amp switch should still suffice, I would use a 20 amp switch. DPST 10 amp toggle switches are readily available at Menards or other similar store. Just connect the 2 poles in parallel to get a 20 amp switch.

You should not enable/disable the PFC bank while in operation nor should you switch in/out capacitors while in operation.

One item that I wish that I would have added is an amp meter connected in series with the PFC bank. This would tell me exactly how much current is flowing through the PFC bank.

FYI, my 6.5 KVA coil (240 volts at 27 amps) needed 200 uF of PFC capacitance which is pretty close to what you think that you need. My adjustment granularity is only 50 uF because I use 100 uF and 50 uF capacitors in my PFC bank.

You probably already know this but PFC does not reduce your energy consumption. It won't make the streamers any longer. I use it to minimize the load on my circuit breakers in the distribution panel so that I can run closer to the load limit without ripping the breaker.

Steve White
Cedar Rapids, Iowa

----- Original Message -----
From: "Daniel Kunkel" <dankunkel@xxxxxxxxx>
To: "Tesla list" <tesla@xxxxxxxxxx>
Sent: Thursday, August 29, 2019 7:51:02 AM
Subject: [TCML]  PFC Cap Bank

I am building a power supply cabinet to handle my next build and I would
like to incorporate a gang of PFC caps with switches to be able to enable
them at will.

Supply current will be 240VAC @ 25amps
PFC will be 276uF according to JavaTC

1) I need to buy some switches but I am not sure how robust they need to
be. How much current will the switches actually need to handle?
2) My assumption is that I should not turn the switches on/off while the
coil is running. True?

Kansas City area
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