Three Phase Induction Motor and a Two Phase Power Supply?

Do you really have a true 2-phase supply, as in 2 separate sources, 4 wires (+ PE), with each phase being 180deg out? Or are you misidentifying 2 hot legs of a 1-phase source as being 2-phase? It's a common mistake, but true 2-phase power is extremely rare.

Either way, you cannot run a 3 phase motor with less than 3 phases. The only reason to consider what you really have is in the solution.

If it is true 2-phase, you can buy a "Scott-T" transformer which will accept a 2-phase input and provide a balanced 3 phase output. You can use Google to find that transformer or a diagram to show you how to make one.

If you have 1-phase power, you will need some sort of phase converter. Your choices are rotary, static (using capacitors) and electronic. The easiest implementation of an electronic phase conversion is to use a VFD. Most will accept a 1-phase input and give a 3-phase output. If you motor is over 2kW, you will need to double the size of the VFD to accomodate the higher current on the 1-phase input side. 2kW and under, the VFDs usually have that capability built-in.

can u please tell why the motor will not start

Because you have one phase less than you should and probably a lot of volts less than you should!!!

Please go and study 3 phase and single phase electrical theory if my answer is not complete enough for you....

the motor will not run and if powered up too long it will eventually burn up. there are several ways to run a motor on single phase power. depending on the application a thre phase Variable speed drive can be used with single phase input, the drive must be two times the motor horse power or KW rating. a capacitor type inverter can be used also. or a rotary inverter. personally I opt for the VSD on the machines that I design.

I just put a Leeson 3 faze speed control on a drill press. Works pretty good. Running it on 110 and the lites dont dim wen I start it up. Givez good tork even at low speed.

Tell us :

What is the phase angle between these<two phase supply >

And you have a NEUTRAL from the supply--which you connect to the motor?

Answer correctly and our replies will follow!

There is plenty of switchgear around that will detect the loss of a phase and either remove the whole supply or give warning or both - if that was the reason for your question.

As mentioned already, the remaining phases will take a lot of extra current, the motor will be loud due to being out of balance and get hotter than it should.

It cannot start either with a phase missing and will get quickly REALLY hot if you try to get it to roll with a phase out!!!!

Your question was not detailed enough for a more exact answer.....sorry.

Do you mean if you have a 3 phase supply and don't connect one phase. ie you have two phases at 120 degrees from each other.

120 degrees :If Stator is STAR INPUT AND you are connecting Neutral wire.

It always disturbs me when the original poster is so vague in the original post and then doesn't answer the questions of obviously knowledgeable people who are willing to help. We've got every possible situation covered in this thread by some pretty good detectives and I'm intrigued by what this fellow is trying to do. Of course, the plain and simple answer is "you can't just hook a 3 phase motor up to 2 phases, no matter what their source, and expect miracles". I'm not trying to chastise anyone here, my frustration is just surfacing. My apologies to all...