318,293. Coates, H. June 2, 1928. Systems for alternating-current motors only.- All phases of a supply to a motor are arranged to be cut-out upon failure of any phase. The supply is to terminals 11, and thence through main switch 14, overload coils 15, contactor 16 and relay coils 21 to the stator. Closure of selector 38 for manual control or through float switch 35 for automatic control, causes coil 20 to be energized over contacts 115, 117 and 48. As soon as relays 21 are energized, contacts 41 close in parallel to contact 117, so that when contact 117 opens due to operation of the rotor resistance 17 under the action of an operating coil 18 and restraining coil 19, the circuit of coil 20 is maintained. Failure of current in any phase causes corresponding relay contact 41 to open and con. tact 42 to close. Closure of anv contact 42 energizes relay 36 over contacts 53. Relay 36 then closes contacts 47 to maintain itself and open contacts 48 to de-energize coil 20 and open contactor 16. Contacts 53 have a time delay in closing so as to prevent inadvertent operation of the relay 36 on starting the motor.