ANTHER RPC question

O.K. Hereis what I have.... An older H-A-S (steelman industries) rpc that has a tag that says, start H.P. 7 1/2, Total run H.P. 21, According to the company rep it has at least a 15 H.P. self starting motor. This thing puts out TOO much voltage on the 2-3 leg (286 volts with my 7 1/2 hp lathe running), 262 volts on the 1-3 leg and 241 volts on the 1-2 leg. It has (8) 60 mf capacitors in it connected across the 2-3 leg. The rep says just drop out 2 of the capacitors. I did that and the voltage balances out almost perfect, 238-245 volts across all three legs under load, but......the converter will not start all the time without all the capacitors...Question...Can I just hook up two of the capacitors in parrallel to a simple flip type switch That I can turn off once it starts up to speed ? Can I just wire the switch inline where the # 2 leg wire connects to one side of the 1st capacitor ? The #3 leg hooks to the other side of the capacitor. Thanks, Dale

Self-Starting RPC

I have an old self-starting Arco RPC that seem to be designed very similarly to yours. Is yours very noisy when idling and quiets down under power?

You might want to look at my thread, because I'm asking substantially the same question:

http://www.practicalmachinist.com/vb/showthread.php?t=171543

And my older thread, with very good informative posts by Peter H:

http://www.practicalmachinist.com/vb/showthread.php?t=170709

You might be able to convert your RPC to balanced operation with a start circuit. That would allow you to balance the output voltages much better. It should quiet down too if it's noisy.

-Jorge

yes, Mine gets nice and quiet and smoother when you put the load to it. With no load it is rather rough sounding and does vibrate more. With two of the eight capacitors disconnected it runs smoother even without a load due to the voltages being balanced better. That is why I want to be able to disconnect two of the eight capacitors with a switch once the rpc comes up to speed (about 2 1/2 seconds). I am NOT an electrician so I thought just addind a switch, if possible, would be easier than building a start circuit by looking at an electrical diagram with all the symbols and stuff that I dont understand. The rpc would start O.K. with all eight caps, then I would just flip a switch wired into a lead going to two of them and then I would have good balance between the phases. Maybe this is not a good idea, that is why I am asking everyone about it, Thanks