ROTARY PHASE CONVERTER WITH TWO IDLER MOTORS ?

Brain Coral

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Hello all,

I recently bought a rather large lathe with a 10hp motor on it. It is a 575v 3 phase motor that I will have to replace with a 10hp, 220v 3 phase motor.

I presently have both, a 5hp RPC and a 10hp RPC. Both work very well. I think that a 15hp RPC would run this lathe, as it has a clutch.

My question is, can I utilize my present 10hp RPC, along with the 5hp pony motor to achieve a 15hp rating, without actually purchasing a new 15hp RPC control box, as well as a 15hp Pony motor?

Brian
 
I've built a couple RPCs now each using two 3 phase motors. For larger HP converters its an advantage because the starting current is much less. I start the small motor just like any RPC then have a delay timer bring the second motor in about five seconds later. On one of the builds I used another delay timer to bring in the run caps after both idler motors were up to speed.
 
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Well, that is encouraging, Karl :)

My knowledge about electronics is limited, so I will have to do some digging around to see what I need. I might have to pick your brain for further details.

Brian :)
 
I am off for a hike in the woods, to place a couple of game cameras, but will be back later on to check in...

Brian
 
Hi Brian,
like Karl said, you can use multiple motors for your function.
you'll spin each motor up individually, then use the entire strength of the combined generative effect to power the 15 hp requirement.
the single phase supply wiring will need to be sufficient for a 15hp load (minimum)
 
This is interesting. I'd like to see a diagram of how it's done. Is it harder or easier to balance out the voltages?
 
Since you will be putting a 10hp 3 phase motor on the lathe and the lathe has a clutch; I don't see any reason why a 10hp RPC won't run the lathe. Try it as-is, I think you will find that it runs just fine. If you have any problems then you can always add a pony motor to your setup but I don't think you'll need it.
 
Well...... I like that ...... I guess that I should at least try it, before going to all of the trouble of making a new RPC. I just have to find the right 10hp motor. Or, I might go the voltage transformer route, as 3 phase 220v motors don't seem to be numerous around here. The local recyclers don't bother setting them aside for guys like us.

With the existing motor at 575v 3 phase and 10hp, if I were to go the voltage transformer route, would I be looking at a 15VAC transformer ? And, do I have to look for specifics about the 575 volts, as well as do some step the voltage down, but not up?

Brian
 
Brian,

Tells us about your "rather large" new to you lathe and how hard are you planning on working it. You might get by with a 5hp motor on it. 5hp 3-phase motors are easier to find. I have a 5hp motor on my Monarch, it will take as big a cut as I ask of it and doesn't seem to notice if I'm taking 50 thou a side or 250 thou a side. Put your 5hp "pony" motor on the lathe and see how she does, Unless you have a 22" or larger swing American etc. may do better than you think.

Mike---reeltor
 
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