Monarch Lathe Electrical Issues

I bought an 18" CW a few months ago and am in the process of wiring it. I'm a home shop machinist and am looking for advise.
The lathe was wired for 440 volts when it was taken out of service. I can rewire the motor leads for it to run on 220 volts but need some help to go further. I currently have a 5 HP rotary phase converter.

1. I plan to buy a larger phase converter. I'm told that due to the older style large frame moter (5 HP) in the lathe, I should buy a 20 HP phase converter. This is to provide enough start up amperage. Does this sound correct?

2. Will I have to replace the heaters and fuses with larger ones?


3. Will size 8 wire be adequate for the path from the phase converter to the lathe moter?

4. Any recommendations for a RPC brand to buy?

Thank you, Greg

20hp rpc seems like a little overkill

it all depends on what the 5hp lathe motor draws.

I have a 15hp phase a matic in my shop. I like it. It works good but the largest motors I'm running are 3 hp.

the phase-a-matics are pretty pricey. you could call them and ask them to size a converter to your needs

another option would be to make your own rpc and save some cash.You can buy the starter panel from a company like american rotary. then add a used 3ph motor that you can easily find online or at a salvage place

I've made a few rpcs with american rotary. You can call them also for advice on sizing, they are very helpful.

Once you decide on what size rpc to get, then you can size the line side and load side wires. American rotary will specify what size wires and fuses are required.

Phase a matic will do the same.

My system starts at a single phase 220v panel,
i have a 2pole 90 amp breaker feeding #2awg wires to a
3phase 60amp fused knife switch. I use the switch to turn on the 15 hp rpc.
from the rpc i feed a three phase circuit breaker panel.
then each lathe, mill or drill press has its own 3ph circuit breaker

I ran my 7 1/2 HP CW for years on a 7 1/2 HP home brew RPC

Machine is clutched so there is not much of a load to start

Yes, replace heaters and fuses for double the amps going from high to low volts

Thank you for the info. It's very helpful.