3 PH motor on single phase??

[rkrieger]

Can someone help a "newbie" with the process of running a 3PH motor on single phase using a "rotary" type converter. I am told that you need another 3PH motor about 150 % HP than the one you are going to use. Also, something about capacitors used to start up the "rotary converter" motor. Particular application in question is a metal "chop" saw with a 7.5 HP 240V 3PH. Motor is an intregal part of machine and is not easily replaceable.

Perhaps a resource location where I can learn about this??

Thanks in advance for any help.

Dick

 

[realolman]

I'm not sure about that large a motor, but there are Variable Frequency Drives that will operate on single phase and power a 3 ph motor.

 

[augie47]

motor

motor

A rotary converter sized to your 3 phase motor woud work. I suggest you might also look at a solidstate adjustable frequency drive. A number of them will operate a 3 phase motor from single phase.

 

[iwire]

I do not know if it is covered or allowed by the NEC but you can just feed the larger 3 phase motor with single phase and then derive three phase from that motors leads to run a smaller three phase motor at it's HP.

The larger motor would not be mechanically connected to anything. It would be working like a motor generator. I believe the capacitors are to help in getting the larger motor turning when it's first powered up.

 

[Rampage_Rick]

http://home.att.net/~waterfront-woods/Articles/phaseconverter.htm

I've also seen apparatus with a single phase motor turning a flywheel attached to a 3-phase motor acting as a gennie. Essentially you'd have 3 spinning shafts once your tool was going.

Personally I'd go with a VFD. All VFDs take whatever incoming AC and convert it to DC stored in capacitors, then modulate it back to whatever output you want. You'd have to oversize it due to the missing leg. (Usually by a factor of 2: you'd need a 15Hp VFD) As a bonus you have speed control if you so desire. They retail for $1000+ but if you move your arse you can pick one up for $200

 

[brantmacga]

I am told that you need another 3PH motor about 150 % HP than the one you are going to use

i believe you're thinking of the HP rating of the phase converter. call the manufacturer of the converter you're going to get and they'll help you determine the size you need.