What happens to the 3-Phase Motor When 1 Out of 3 Phases is Lost?

When one phase of a three-phase motor fails due to fault(s), the remaining two-phase supply is still connected to the machine which is known as phase failure or single phasing which is a common fault that occurs in three-phase induction motors.

The motor will continue to run with vibration and reduced speed.

The motor will operate in normal condition without any damage if 33% load (1/3rd of rated load) is connected to the three-phase motor. But still, the speed will reduce with noise and vibration as current increases in the remaining two phases which will heat up the internal parts of the motor.