3HP or 4.5HP, or something else entirely?

MrWhoopee said:
I see what appears to be a cord with plug attached. Is there a reason we're puzzling over the motor wiring?
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The original question I had was just to confirm the motor was a 3HP motor (at max) as I'm chatting with a tech from American Rotary to make sure I'm right sizing my new RPC.

I do have 2 wires that I need to figure out on the motor itself as I forgot to start labelling them until I had take 2 wire nuts off, but 2 out of 6 isn't terrible. Also, wasn't asking about that yet.
 
If the RPC is just to run a single machine, may not be cost effective. They will probably recommend a 7.5 Hp RPC for a 3 Hp motor, typically size the RPC to 2X the motor load, but there are other factors such as starting load. A 3Hp single phase input VFD will run around $250-300 for a mainstream brand. RPC will be about 3X the cost if new and shipping can add up. They do sell an RPC controller if you can find a decent idler motor.
 
mksj said:
They do sell an RPC controller if you can find a decent idler motor.
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This is something I need to look into . Years back , I bought a 15 horse RPC . Right after I did , people told me they were easy to make . My Uncle had 100s of motors back then and they would have worked I'm sure . I can get the motors if they are 3 phase .
 
mksj said:
If the RPC is just to run a single machine, may not be cost effective. They will probably recommend a 7.5 Hp RPC for a 3 Hp motor, typically size the RPC to 2X the motor load, but there are other factors such as starting load. A 3Hp single phase input VFD will run around $250-300 for a mainstream brand. RPC will be about 3X the cost if new and shipping can add up. They do sell an RPC controller if you can find a decent idler motor.
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Yeah. I had a little discussion around RPC or VFD in this thread: https://www.hobby-machinist.com/threads/powering-a-gorton-9j-mill-4-motors.100670/

Overall, consensus seemed to be that given this thing has 4 motors, and it's already completely wired for an RPC (it's what the previous owner ran it with), it was easier to go RPC. I would also like to look for a decent lathe in the next few years, so a decent sized RPC wouldn't be a bad thing to keep options open for the lathe.

All that said, a VPC makes more sense in my head, just seems like it would require way more time investment in this mill to get it back to making chips.

mmcmdl said:
This is something I need to look into . Years back , I bought a 15 horse RPC . Right after I did , people told me they were easy to make . My Uncle had 100s of motors back then and they would have worked I'm sure . I can get the motors if they are 3 phase .
Click to expand...

Yeah. This is another of those things where I think I'd rather the time savings, and the added cost (plus peace of mind knowing something I did isn't going to fry my mill motors). Hence why I'm leaning towards using American Rotary.

Appreciate all the input though for sure. I'm a completely rookie to all of this world (machining & 3-phase), so I appreciate any and all insight.
 
Just in case you're not confused enough, once the largest motor is running it will function as an RPC, allowing you to start the smaller motors. I use my mill that way. It starts with an SPC, then I leave it idling while I run my lathe.
 
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