Does anyone know about three phase motors? I was recently given two, three phase motors, I have several single phase motors but have never played with the three phase kind. What are they normally used for, and is there any use for them around a garage?

 

Three phase motors require three phase power. Normal household power is single phase with 180° polarity difference between the two power legs... 220 volts with a center tap for 110 volts (or 240/120v). Three phase is set up with a delta or wye configuration with a 120° phase shift between each leg.
You would have to run a phase converter to go from single phase to three phase.

 

In other words there is no use for a three phase motor at your residence. Factories use three phase motors because they are very efficient and easy to reverse etc. To reverse a three phase motor all you have to do is swap two of the three power wires.

Phase converters are expensive and inefficient.

 

Three phase motors are not cheap and are useful, even on house current provided they are 220 volt and not heavy industrial 440 only. However, some have have an internal board where the contacts of some 440 volt motors can be switched to run on 220 voltage.
Somebody mentioned the magic word - Phase Converter. There are (2) basic types. Electronic and rotary. The electronic will allow running 3 phase motors of a very narrow power range, while the rotary will run other 3 phase motors from fractional to that of the HP rating of the rotary unit itself.
Delta wound motors are prefered for the slave or generator rotary.
Because there is hardly a nickels worth of difference between a 3 phase motor and a 3 phase generator it is not difficult for a guy to make his own phase converter and did I see where a ford truckin guy was given two of these gems?
Yes, they are not as efficient as having true 3 phase current - they are 85% efficient.
The trick to starting a 3 phase motor on single phase is by using one or more capacitors on one leg of house current. Once started, the 3 phase motor will idle on single phase. While idling, the third leg is being generated.
If a guy was given a 3 phase of 3 horsepower or more he is well on his way to building a phase converter.
I built a 5 hp. 20 years ago and still use it today to power a milling machine, lathe and surface grinder. The lathe is also 5 hp but I use (6) 370mfd oil caps. on the output side for power balancing.
Six of my friends have built these also and every body's design is slightly different, but all power machine tools daily.
Be aware these things powered municipal electric trolleys all over the country from about 1900 to as late as the 60's in some areas.
If you are interested in building a phase converter, research the subject. There are even plans is back issues of either Popular Mechanics or Popular Science and Lindsey tech. publications.
If a guy can do his own home wiring, he can build a phase converter.
If interested, give ole Shoptowel a shout on this thread and I'll pass along more how-to info.

 

Yes, if you have three phase machines to run they can be useful... -hehe

 

If you want to set up a home machine shop the motors might come in handy. Either as a component in a rotoray phase converter or a replacement motor.
Used Milling machines,lathes, surface grinders and industrial drill presses are more often than not powered by three phase motors.