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Rotary phase converter questions

EliG

Plastic
Joined
Apr 4, 2017
I am slowly gathering the components to build a 10 hp self starting RPC to drive the 7.5hp motor on my lathe. I have the 10 hp idler but I want to make sure I have the main contact or sized correctly. The label on the motor lists the full load current at 28 amps. So (28 amps) x (1.73 factor due to single phase use)=48.4 amps. This contactor will only have the power to the idler passing trough it and that leads me to want to use a NEMA size 3 contactor.

Can someone explain how the ratings for a potential relay work? I see the Steveco 90-66 mentioned in several posts. I understand that this has been discontinued and am trying to fugue out water a suitable replacement would be. This will be driving a separate contactor for the start capacitors so the coil needs to be separate from the contacts in the relay.

I will try to post a wiring diagram if I can get it to work.

Thanks,

Eli
 
Depending on the machine, you may want to consider a larger idler. You may have some troubles starting the lathe on high speed, depending on whether it has a clutch or not..
 
Thanks for the suggestion. This is on a Boye and Emmes 24"swing cone head lathe that is geared quite low. I picked up my 10 hp idler motor pretty cheap and figured if it didn't work well I would either add an additional 5 hp idler motor or I checked tonight and I should be able to up size to a 15 hp idler with the main contactor I have selected. This assumes that I have been doing my current calculations correctly for single phase loading a 3 phase contactor. I would of course need to modify my start and balancing capacitors if I upgrade to a 15 hp idler. I am using the Fitch Williams method for selecting my start and balance capacitors.

Eli
 
Idler Motor as Phase Converter - wiring to sub panel

Does anyone have a simple wiring diagram for how to wire from the three legs of the phase converter, in this case I'm using an idler motor, to a 3-phase sub panel. I would like to add several outlets from breakers in the sub-panels to run more than one machine.
 
I am slowly gathering the components to build a 10 hp self starting RPC to drive the 7.5hp motor on my lathe. I have the 10 hp idler but I want to make sure I have the main contact or sized correctly. The label on the motor lists the full load current at 28 amps. So (28 amps) x (1.73 factor due to single phase use)=48.4 amps. This contactor will only have the power to the idler passing trough it and that leads me to want to use a NEMA size 3 contactor.

Can someone explain how the ratings for a potential relay work? I see the Steveco 90-66 mentioned in several posts. I understand that this has been discontinued and am trying to fugue out water a suitable replacement would be. This will be driving a separate contactor for the start capacitors so the coil needs to be separate from the contacts in the relay.

I will try to post a wiring diagram if I can get it to work.

Thanks,

Eli

Potential relay problems could be eliminated with a manual push button activation of the start caps.
 








 
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