# My RPC



## Tony Wells (May 23, 2011)

I like the way you mounted the motor. It wouldn't even appear to be a RPC from just a glance. Looks more like a small hydraulic power unit. Clever layout. Good job.


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## Zigeuner (May 25, 2011)

That's very nice work. I'd be interrested in knowing what sort of capacitance you wound up with for start and run. I have a 5 hp RPC that I built and it uses a total of 560 Âµf for start and dual 50 Âµf run caps: one across L1 - L3 and the other across L2-L3. I use a Steveco 90-66 Potential Relay and a definite purpose contactor for automatic starting. The unit has been running now for over a year with no problem whatsoever. It powers my 3 hp Webb 4VH Mill. I also added a control transformer so that I could have a neutral for the 120 VAC coil on the contactor. 

If you have a schematic, I'd like to see it. I've been collecting them as I plan to build another, larger RPC at some point. 

I like the way you mounted the motor to cover the rotating shaft. I used some plastic fittings. I don't like cutting off motor shafts. My unit is also very quiet. The motor is a 1750 rpm, which I recommend for an RPC rather than a 3,600 speed since they are much quieter. 

Here is my solution to the rotating shaft issue. The motor is mounted in rubber isolators. I had to build my own mount since the motor was a flange mount. It was a bargain at $100 plus shipping for a NOS 5 hp Boston Gear motor. 




Here is the basic schematic I used. It's a typical autostart design that I found on the internet.


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## Zigeuner (May 25, 2011)

[quote author=Jim B. link=topic=2248.msg15032#msg15032 date=1306341416]
I do know that I used 6 X 15 uF = 90 uF as the start capacitor. I would need to take apart to find the out about the balancing caps.
[/quote]

That's correct for a 1-1/2 hp motor. My 5 hp needed more than 500 Âµf to start up. The voltages under load are all close to 240 VAC so I didn't do anymore balancing.


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