Would this motor be good for a rotary phase converter?

[Charles (in GA)]

Brand new, old stock, still bolted in the original crate, even comes with a lifting eye and key taped on the shaft.

WEG brand, 5 hp, 1720 RPM, 3 phase, real tank of a motor. $85, might be able to get it for a little less.

Been thinking about trying to build one to power three phase stuff. I know that the Practical Machinist web site has a whole forum devoted to this stuff, but I've never participated over there, so I thought I'd ask here first.

Don't start the stuff about VFD's and everything else, don't care about them, not interested......... all I'm asking is if this would be a decent motor for a RPC that would allow me to produce enough power to drive a small lathe or mill?

Charles

 

[jabberwoki]

I think you have to use a single phase motor to run the converter?

 

[Charles (in GA)]

I think you have to use a single phase motor to run the converter?

No, you use a three phase motor, supply two of the three fields with the two hots of a 240v single phase circuit and the motor, free spinning, generates the third leg of the three phase.......... that I do know.

I'm just not sure if this motor is large enough to do the job, or if I need one larger, such as a 7.5 hp. I know that depending on how you wire it up and capacitors you do or don't use, the motor will be self starting or may have to either be started with a lawnmower pull rope or a small pony motor to get it spinning.

Charles

 

[930dreamer]

Yes, it will work,how big will the lathe/mill be? I"ve looked on You Tube also, there's a few videos with a RPC starting lathes etc.

 

[jabberwoki]

I`ve heard the motor you use must be the same hp or greater than the one your powering

 

[930dreamer]

I`ve heard the motor you use must be the same hp or greater than the one your powering

On my 5 hp air compressor I started with a 10 hp idler because it's a "hard start" piece of equipment.

 

[A_Pmech]

That motor will make a nice converter. The only question is will it be big enough?

What do you intend to run with it?

 

[rsanter]

makes a great converter for running about a 3-4hp piece of equipment.
you can use a static converter with this motor and allow the losses to occur in this one and have full rated power with the motor in the equipment.

I had a static converter on the 3hp motor of my lathe. I wired the 1hp motor of the mill to the motor of the lathe and then put the lathe in neutral. start the lathe motor and I had a cheapie rotary converter for the mill
worked great

bob

 

[Charles (in GA)]

That motor will make a nice converter. The only question is will it be big enough?

What do you intend to run with it?

Dunno know......... how much hp is a modest size Bridgeport or similar mill, or a "small" lathe (like OCG's Clausing Colechester Now that would be the cats MEOW for sure!)

The guy has my card and phone numbers. Said he had a couple of others, thought they were all 5 hp but was going to look and call me. First time he was ever at this flea market, said his buddy talked him into coming. I didn't get his name or number, hope he calls me. Probably should have bought the motor, it seemed like a reasonable price.

Charles

 

[larry_g]

That looks to be a lot like mine. I built a 5hp converter with the Hanrahan plan and I have been using it for 10 years without a hitch. Most bridgeports are in the 2-3hp range or less and a 13" lathe will usually be in the 3 hp range. I also run a bigger hz mill with mine and once I took the controls off the generated leg it works fine. At that price I would say jump on it.

lg
no neat sig line

 

[930dreamer]

If two 5 hp are available, use both and have a 10 hp for future equipment.

 

[Norcal]

Only bad thing is it may be too small.

 

[A_Pmech]

Dunno know......... how much hp is a modest size Bridgeport or similar mill, or a "small" lathe (like OCG's Clausing Colechester Now that would be the cats MEOW for sure!)

The guy has my card and phone numbers. Said he had a couple of others, thought they were all 5 hp but was going to look and call me. First time he was ever at this flea market, said his buddy talked him into coming. I didn't get his name or number, hope he calls me. Probably should have bought the motor, it seemed like a reasonable price.

Charles

A Series I Bridgeport will be no problem.

Lathes, it will depend on whether the machine has a clutch or not. Generally, with a clutched machine you can get away with 1 converter horsepower to each spindle horsepower. If no clutch, 2 converter horsepower to each spindle horsepower or you won't be able to get the machine to start in high gear.

 

[cnc-me]

WEG's are good motors, made in Brazil.
That 5 will start a 3 H.P.

 

[rsanter]

most bridgeports are 1 or 2 hp. with what you have you would be set
most lathes that you would get for a garage would be 1 to 3 hp so again you would be set

bob

 

[lametec]

Dunno know......... how much hp is a modest size Bridgeport or similar mill, or a "small" lathe (like OCG's Clausing Colechester

Bridgeports range from 1 HP to 4 HP. with most being 2HP or less. Some clone Series 1's are 3 HP. A BP Series II is typically 4HP.

As for OCG's Clausing.. that's probably a 7.5HP lathe. I have an older Colchester 15 x 48 that has a 7.5HP motor, and I run it off a 20HP RPC (only because I came across the 20HP motor for $75).

Personally I'd shop around for a bigger motor. You should be able to pick one up for the same price (or even less) than you would have paid for the 5HP.

 

[Charles (in GA)]

Update. Well the Flea was busy today, and the guy with the motor was back. I went ahead and bought the motor for $80. It will sit for a while as I have other issues to solve first (shop heater and rebuilding two Lincoln floor jacks), but I at least have what I think is a quality motor capable of what I want.

The guy also had a three phase motor today that was 1-1/2 hp. It was huge, much larger than this 5 hp. I'll bet the motor alone weighed 100 lbs.

Charles