Electrical Interview:3-PHASE INDUCTION MOTOR ACTS AS 2-PHASE

              When a three phase supply is applied to the induction motor,the 3-phase winding (120 degrees) produce three phase magnetic flux. Let the maximum value of flux due to any one of the three phases be 

and the total resultant flux in air gap is 1.5 times of maximum flux  .If one of the phase in 3-phase  suddenly damaged the induction motor acts as 2-phase motor. Because the motor produce 2 phase flux in air gap,the total resultant flux in this 2-phase case is only .Due to that the speed in 2-phase motor  is reduced as compared to the 3-phase induction motor.

                                       
                                                   3-phase motor resultant flux is = 1.5 times maximum flux.

                                                   2-phase motor resultant flux is = maximum flux.