I'm interested in learning what happens to a three phase motor if one phase loses power 1) while running, 2) prior to start?I've I've got a three phase motor with only two phases still good, can I manually rotate it to give it a quot;kick startquot; so it will continue to run in two phases?
While you probably *can*, it's not a good idea. When one phase is lost, a loaded three phase motor cannot start or may stall under load...the current flowing in the remaining winding(s), will increase to 600% of the nameplate rating...Winding insulation subjected to locked rotor current may fail in as little as 15 to 90 seconds. This winding insulation damage is permanent and cumulative. Motors should not be started during phase loss and if they stall, they must be disconnected immediately. the life of a motor operating with a 3% continuous voltage unbalance (at full load) will be cut in half.
In case it's a Delta wound Motor the current going through each phase will exceed the designed current.It willcontinue to run for some time as the rotating magnetic field will still be produced and then one phase will blow and the motor will stop.This will be true for case 1 and 2 both. In case it is a Star wound motor the rotating magnetic field will no longer be produced and the motor will not run.True for 1 and 2 both. You can't give it a kick start to run.Thats true only for single phase motors which either need a manual starting torque or a capacitor toprovide it.
