My upgraded RPC is up and running

[Investigator]

Got it almost finished. I now have a push-button start, 7.5hp RPC. I have a couple more little things to finish up but I hooked it up and tested it and all is running well. My voltage readings are:
L1-L2 250V
L1-L3 216V
L2-L3 208V
and that is totally unbalanced, no run capacitors at all. I'm running this in order to use a 12" Logan lathe and a Bridgeport clone knee mll. I have no electronics to run.

So, do I need to add caps?

Pics when I get it all done tomorrow. I'm going to add some meters/displays so I can see the voltage and amps on each line.

 

[Ulma Doctor]

these machines will operate just fine on the unbalanced RPC
just remember, don't use the generated leg to power a transformer.
only use the supplied single phase legs for transformer power

 

[benmychree]

I would add some caps, they likely would make starts and reversals function better.

 

[Investigator]

For the sake ok argument, if I wanted to balance it out, where do I start?

 

[Canus]

I'm with Investigator here. I built a 10 hp RPC and have partially balanced it using caps but would like to fine tune it to get the voltages closer to each other. Any tips on selecting caps for final tuning would be greatly appreciated.

 

[Ulma Doctor]

I would add some caps, they likely would make starts and reversals function better.

how much capacitance would you use and between which phases?

 

[Weldingrod1]

Add capacitance to the low leg. Total and complete swag: 10 uF.
Hopefully someone with a RPC will chime in.

Sent from my SM-G892A using Tapatalk

 

[pontiac428]

If those voltage readings are from a no-load condition, they won't mean anything. What are they under load?

 

[Investigator]

I'm with Investigator here. I built a 10 hp RPC and have partially balanced it using caps but would like to fine tune it to get the voltages closer to each other. Any tips on selecting caps for final tuning would be greatly appreciated.

how much capacitance would you use and between which phases?

Add capacitance to the low leg. Total and complete swag: 10 uF.
Hopefully someone with a RPC will chime in.

Sent from my SM-G892A using Tapatalk

If those voltage readings are from a no-load condition, they won't mean anything. What are they under load?

Well, I'm not saying I want to, or that I even think I need to. Fact is that same voltage setup has ran my Logan 12" for a couple of years. I'm more wondering about the academic argument of how really.
It's my understanding that you can never completely balance an RPC due to the various loads put on it normally. I've even read one opinion that it is a complete waste of time.

Pontiac, I haven't got everything finished yet. Still need to add 3 combo voltage and amperage meters, then I should be able to read it off the panel all at once.

 

[zamboni2354]

I think it's a little trial and error. For my 10hp converter I ended up with 100mf between L1 and L3 and 170mf between L2 and L3
.
Here's how mine turned out.

Jeff

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