electricpete, thanks for that suggestion. I think delaying the openning of the contacts (after the motor has tripped)might resolve this.
edison123, keeping the contacts closed all the time will adversely affect the starting current (will be high) and starting torque (will be low). For a slip...
there is a situation of a 15MW slip ring motor (uses liquid rotor starter) that has its slip ring shorting contacts sparking/ flashing - mostly when the motor trips from full load. On few occations they also spark during startup but this is not frequent. As a result the contacts need to be...