3 Phase Induction Motor

Let's all take a wild guess. You go first.

motor will shutdown due to over current of 2 active lines carrying the load of the cut line.

If you have also a phase relay, it will shut it first preceding over current device.

Do your own homework.

You will get dramatically less current flowing to that phase source. There will also be a nice big spark at the contacts that interrupted this current flow.

One might even loose their job after the debris cools down.

Is the phase cut with a hacksaw?

Then the motor will run only at 2/3 speed and torque. To re-connect the cut phase, wet the conductor with distilled water and glue it to the terminal with a quality animal hide glue.

After you get up off the floor from the arc flash call a qualified electrician and send your resignation to your employer.

Funny. The available torque may be reduced but we do not know if this three phase motor is wired in either a wye or delta configuration. This along with the location in the circuit that either a power or motor phase opening occurs will make a considerable difference in the failure mode.

Depends on; 1) when the phase is "cut", and 2) how much load is on the motor. If it has already begun to rotate and the motor is unloaded, you may not notice the difference. If there was a load on it, and the load is over 50% of the rated capacity of the motor, it will overload the motor. If the motor had not begun to rotate, it would not likely start to because there is no relative rotation any longer, so it would shake back and forth pulling locked rotor current on the other two phases until a fuse blows or a circuit breaker trips. If it accidentally does begin to rotate because of something in the load, it can do so in either direction at random, but that load will likely cause the motor to overload.

It might act squirrelly, Bawankule.

The electrical load on that phase will drop to zero.

Where is the rest of your question?? your request is incomplete, because it has to be part of the whole given data about the working conditions of your 3 phase induction motor,.... Also, you just mentioned the section "a." required in your question,,, Are there no "b" and "c" left??

In a 3 phase motor, if there is no supply in one of the phase - say R phase of RYB, for example 440 VAC supply. ! phase winding will get 440 VAC and other two winding, in series will get approx. 220 VAC.

If proper controls are there for single phasing. motor will shut off in microseconds w.r.t. timing of phase device. in control. But if the old type, where only one phase is used for single phasing, it may stop or may not stop. Current in three winding may not be equal and unbalanced current control may work and stop the motor.

If proper setting are not in place it may run the motor, at no load or at any part of full load it may burn due to 'single phasing'. Time to burn one of the winding may vary with the load on the motor.

As 3 phase motors are not suitable to run with two phase supplies, torque , speed and other performances are of no relevance.

Small or F.H.P motors can be run on two phase or one phase with properly calculated capacitor for micro farad and volts, here motor can run on derated HP/ output and full load rpm, starting torque ultimately full load torque. We did try single phase motors with three phase style winding for ease in production and reducing winding wire consumption.[overhang portion of winding].