Upgrading my simple RPC, questions

I built my rotary phase converter 25 years ago using a 10hp cast iron framed motor. I could never figure out the specs on the voltage controlled relay so I used a timing relay instead. It took some experimenting of adding and removing the run capacitors to balance the three legs. I have several VFD's now but I still use my RPC every time I go to the shop.

https://www.ebay.com/itm/7-5HP-Rota...134475?hash=item264360300b:g:rzQAAOSwo4pYNIuX
$119.50 doesn't sound like a bad price to me for a 7.5hp RPC kit. It does have a voltage sensing relay so it would be a single button start. What the kit is missing is the start / stop buttons but you can grab those from any motor contactor box. Capacitors aren't cheap if you order new ones and the caps in this kit are rated for 370vac. I blew several cheap 220v caps trying to save a buck when I was building my RPC. It didn't take too long before I just paid the premium for higher voltage capacitors.

For a first time RPC builder I think that kit sounds like a great deal! I would have bought one if there was one available 25 years ago!
 
the cap and switches are fine, the contactor needs to have a 220v coil , unless you plan on utilizing a step down transformer.
the cap and switches are fine, the contactor needs to have a 220v coil , unless you plan on utilizing a step down transformer.


the 40 amp would suffice, if a 50 amp can't be easily located

my plan is to use a single hot leg from the contactor to power the coil.

Now, I just need an enclosure. I'm not sure if the one I currently have is big enough. On that note, is there any requirements that the enclosure be metal? what about plastic or even wood?
 
my plan is to use a single hot leg from the contactor to power the coil.

Now, I just need an enclosure. I'm not sure if the one I currently have is big enough. On that note, is there any requirements that the enclosure be metal? what about plastic or even wood?
NOTE:
The single hot leg through coil would need to meet up with the neutral wire to get 120v.
you can't just ground one side of the coil and put 1 leg of the 220v supply circuit to it, and have it function correctly.
This would require a 4 wire 240v supply to get usable 120v from 240v single phase

Plastic Nema enclosures are relatively cheap on amazon.
 
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Surplus center also usually has cheap capacitors, usually some in the 370v range, if you want some extra protection instead of running close to the upper limit of a 250v capacitor
 
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