[SEL] Air compressor motors

[jbcast at charter.net]

---- JIM KIRKES <jd.kirkes at verizon.net> wrote: 
> Hi Tony,
> 
> Curt Holland had a very nice write up on making a single 
> phase to three phase converter.  I took a look at his 
> website and couldn
> find it so maybe he can point you in the right direction.
> 

> I attended a nearby community sale yesterday and ended up 
> dragging
> home a huge behemoth of an air compressor.  It's a Curtis 
> 2-stage, 80
> gallon upright.  It wasn't until I got it home and unloaded 
> it that I
> realized the motor on it is 3 PHASE.  I can't run 3 phase in 
> my
> garage, so if anyone has a single phase motor that would 
> work for
> this application, I would be interested in buying or trading 
> for this
> 3 phase unit.  The motor is rated at 5 HP.  I don't know 
> much about
> the particulars of electric motors, but I'm guessing I'd 
> probably
> need a single phase motor with more HP than the 3 phase 
> motor I'd be
> swapping out...  Can anyone confirm that?  Here is some of 
> the
> information on the motor tag:
> 
> Frame- 184T
> Horsepower- 5
> Volts- 208-230/460
> Amps- 14.8-14/7
> RPM- 1725
> NEMA nom eff. 81.5%
> Rating- 400 AMB-Cont.
> PF- 80%
> 
> I'd also be interested in trading the whole compressor unit 
> for a
> complete single phase unit if anyone is looking to upgrade. 
> I do not
> need a compressor this large, but I got a pretty good deal 
> on it, so
> I bought it anyway.  I won't need anything more than a 60 
> gallon
> single stage for my uses.  I can provide pics of the motor 
> or the
> whole compressor if anyone is interested.
> 
> Thanks,
> 
> --
> Tony Kimmell
> Bloomington, IL
> 
Tony, a convertor is not usually suited to a compressor. Arotary convertor would require at least a 7.5hp idler motor, thiw would have to run all the while the compressor is being used. A static convertor reduces the ouput of the 3 phase motor so it wouldn't run the compressor, on a mill or lathe you seldom need the full hp, a compressor does. Since you don't need the full ouput of this compressor I would look for a 3hp moptor and a smaller drive pulley. A 5hp single phase should work in place of the 3 phase with the same pulley, hp is hp. It will pull more amps on the 2 legs, but the total will be close to the 3 phase on three legs. The smaller motor should be cheaper and easier to find, the smaller pulley will reduce the load on the motor, you will have to check the amps under load to be sure it's not overloaded. Ssmaller pulley =l reduced load, lower amperage,  compressor turning slower, reduced output. Single phase motors are usually harder to find used, most people can't use 3 phase at home.
J.B. Castagnos
Belle Rose, LA