Running of 3 phase motor by using two phase supply

Not sure where your at that this kind of thing could happen daily.And I have never heard of a device that can do what you are asking.

However you could simple wire a switch inline which would have both wiring configurations going to the motor and simply flip a switch when this occurs.

Since your working with both 3 phase and 2 phase I would suggest using a 3 pole double throw switch and wire one side for the 2 phase configuration and the other for a 3 phase configuration. That is if the ampacity of the both configurations can be handled by the one switch.

Hope this isn't too confusing.

I also have never heard of this, nor a device for it, but Perhaps he can run with your idea of a switch, and instead use a relay that is controlled by the 3rd leg.

Make your own phase converter

rectify the pases coming in

use a 3 phase PWM to recreate the 3 phase

this is how VFD's and normal phase converters work

since its rectified it shouldn't care if 2 or 3 phases are coming in since it is just making DC

Analog Devices makes an Arm7 with a 3phase PWM block built in

you'll have to spec out transistors or FETs to suit your power needs

clear, comprehensive.

PLEASE DISREGARD THE DRAWING IN MY PREVIOUS POST, AND REFER TO THE DRAWING BELOW. I was in a hurry Friday and connected the capacitor to the dead phase, which does nothing. The capacitor needs to be connected (via relay contact) from a good phase to the motor's third leg.

you need to understand@ the 3 phase Ac power i.e electrically phase displaced by 120 degree.

Your problem is for power cut by grid,at which instant , the grid supply remain between any of two phase., i.e for lighting /fan (Single phase load) supply can be used between phase and neutral during that time .

To use connected load on third phase for lighting / fan (Single phase load) either you can have COS linked with electrical /mechanical interlocked. IN no case the Two phase you referring which means electrically 180 degree phase displaced power can be distribute by grid. And motive power should not used with with 2phase i.e 415 volt two wire, against the original requirement of 3 phase , 3 wire requirement.

nascon

Hi there.

I'm not an electrican, however, years ago, I had a friend that ran a 3ph mill press from a 1ph supply through an inverter. The inverter was an early model and only produced (so I am told) 2.5 ph. To correct this problem, he had a spare 3ph motor between the inverter and the mill press running on idle (no load) that genereted a true third phase. Perhaps an electrical mind could jump in here and work it out.

You only have to oversize the motor and it will be able to run on two phases as an Arno-motor.

Not sure of your supply, but a 3 phase service, that loses a phase, does not create a 2 phase service. For the sake of argument, let's say you've got a 3 ph, 480 volt service. If you lose a phase, you have 480 volt, single phase. Any 3 ph motor will run on single phase power, but it will eventually burn up.

Load Controls Incorporated, is a co. that has a unit that monitors horsepower, which will also let you know of a phase loss. This unit has a selectable output (0-1mA, 4-20mA, 0-5 or 0-10 volts), which can be incorporated in the circuit design to activate a switch, changing the power ckt from 3 phase to single phase.

Just for clarification...

Some people have gone off on the tangent of explaining to you that if you lose 1 phase of a 3 phase supply, that is not called "2 phase" because 2 phase is something entirely different and very rare. When you lose 1 phase of a 3 phase supply, the result is called "single phase". Your mis-naming of the issue is a very common semantic mistake, but don't worry about it. While this is technically correct, I think they are missing your point. As I interpret your issue, you have a 3 phase supply and occasionally lose one phase, but you want to keep your motor running nonetheless.

The capacitor method described above will work, but there is a concern. The LOAD on the motor must be reduced by the square root of 3 (reduced to 58% of normal) in order for this to work without causing the motor to lose torque, drop into higher slip and overheat. If your motor is already considerably oversized, this will work fine. If not, it may not work at all unless you can shed load.

A better alternative, if this is a pervasive problem, is to use a VFD for the motor all of the time, even if you never change the speed. A VFD changes the incoming line power to DC, then re-creates an AC pseudo-sine wave for the motor. In the conversion process (going from AC to DC), it can do that with 3 phases or 1 phase, as long as the components are sized properly. If the motor is equal to or less than 2.2kW @ 240V, most VFDs can do this without de-rating. If it is larger, you must double the size of the VFD for the motor so that the VFD can adequately handle the extra current and extra ripple on the rectifier side when it has to draw all of the incoming power (1.732 times normal) through only 2 of the phases instead of all 3. So by using a properly sized VFD as the motor controller, your motor would never know that a phase on the input side had been lost, it would continue on running seemlessly.

The use of a VFD is truly an option, if money is no object.

As far as a tangent goes, I believe someone needs a Websters. It's called single phasing because the energy is generated thru 1 winding.