Rotary Converter Advice Needed

[Bib Overalls]

About a year ago I bought a well used ACRA mill. It has a two speed (1725/3450) three phase 240 volt motor rated at two horse power. I have been powering it with a simple rope start rotary converter made out of a 1725 RPM three phase motor rated at three horse power. The mill runs strong on the slow setting but seems to struggle on the high side.

I just acquired and old Colchester Student lathe. It was originally had a three horse power three phase 1725 RPM motor. Somewhere along the way someone swapped in a two horse power motor that, running off a buzz box, produces one and one third horse power. With this set up the lathe is a dog. I have a three horse power 1725 RPM three phase motor that I am going to install.

My intention is to power both the lathe and the mill off of one rotary converter with a five horse power idler motor. Is this sized motor adequate for my application?

I have located a 220 volt, five horse power Baldor three phase, 3450 RPM motor at a good price. Is this a suitable motor for my application? Will the higher idler RPM solve the mill's high speed power problem?

Any help appreciated.

 

[930dreamer]

I saw your post on the PM also. I'm not sure how the RPC will act on a two speed motor. I'd sart the 5 hp motor(idler) without the panel your looking at, and test it on the two machines.

 

[rsanter]

Don't bother with a RPC
Just get a VFD and be done with it

Bob

 

[larry_g]

I run my shop on a home built RPC. I have a two speed motor on my mill and it has no problem with either speed or plug reversing. The idler motor speed will have little to no effect on the motor driven. Are you running balance caps on your RPC? They go a long way toward keeping the generated leg from sagging. When your motor is struggling have you measured the voltage on all three legs?

lg
no neat sig line

 

[Bib Overalls]

Thanks for all the advice. This morning I talked with Jim Goreman at Phase-Craft. He sells on eBay and invites questions about sizing, wiring, etc. His number is 714-710-9094. Jim spent some time with me and fully explained what I need. I bought a 5 HP 3600 panel from him for $140. The other phase converter vendors that I looked at on the net did not offer RPM specific converters. I am going to run #8-2 W/G NMC from the service panel to the control panel. I got a good deal on the wire; $.90 a foot.