Selecting a motor for rotary phase transformer

Ignoramus5833 · 2005-07-26T16:57:37+00:00

I am going to build an RPC. I will go to an industrial junk yard topick a used 3 phase motor, tomorrow. I do not want to buy a wrongmotor. Some questions, possibly very ignorant:1. Is TEFC better than drip proof, for me?2. Is there a difference in wye vs delta wound, as far as I am concerned?3. Do I need ball bearing or I can get away with sleeve bearing(remember, it is an idler, no load or thrust on shaft other than atstartup).4. What HP to choose? With these motors essentially free, the costdifference between 10 and 7.5 HP is minimal. 10 HP, though, draws alot more current at startup. My garage has a subpanel that is on a 60amp breaker.5. I salvaged a 1/4 and 1/3 HP motors from two broken vacuum pumpsthat I had. I would buy a 5/8" ID pulley on one of them. Would they beable to spin up a 7.5 or 10 HP motor? Jim Rozen reportedly used a 1/4HP pony to spin up a 7.5 HP motor, that makes me hopeful.6. How fast would the idler need to spin before I can remove the ponyand apply 220V to the idler input?7. Is there something that I forgot to ask?thanksi

Jul 26, 2005 21 Replies

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Ignoramus23077 21 years ago

no wonder it's free. I got a 10 horse motor today for $40, and I can actually carry it (barely). Also got a 7.5, that one is "light", comparatively speaking. See my another post "BOUGHT motors and stuff for PHASE CONVERTER".

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Christopher Tidy 21 years ago

I guess I'm a sucker for old stuff. I love the solid construction and the brass fittings on these old motors. The 2.5 hp motor probably weighs

150 lbs (at a guess), but this one is upstairs. If I get it I reckon I'll bolt it to a board and slide it down the staircase using a chain block.

Chris

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