Question

If one of the phases of the supply breaks down, then the connected three phase induction motor ____________

(a) continues to run as a single phase induction motor, provided load does does not increase beyond 57.7%

(b) stops operating after few seconds

(c) continues to run as single phase induction motor

(d) continues to run as two phase induction motor

I got this question during an interview.

Asked question is from Cooling (Loss Dissipation) in chapter Rating and Loss Dissipation of Electrical Machines

Answer 1

Right option is (a) continues to run as a single phase induction motor, provided load does does not increase beyond 57.7%

To elaborate: When one of the phases breaks down then the other two phases will supply the rated current but the load should be reduced to 57.7%.