Motor starting system including thermal responsive means for selectively disrupting the power being supplied to the start winding

Claim 1

A motor starting system for use with an electric motor having a main winding and a starting winding, said system comprising: a capacitor connected in series with said starting winding for shifting the phase of current applied thereto, a mass of material which has a resistance characteristic having a positive temperature coefficient and a sharply defined transition temperature above which the resistance of said material increases sharply, said mass being serially connected to said starting winding and to said capacitor and having a preselected nominal resistance when heated to establish a reduced flow of current to said starting winding in order to provide a torque contribution during continuous running of the motor while permitting operation of said capacitor at a reduced voltage level, said mass being arranged in a preselected physical configuration including a neck portion having a substantially reduced thickness to provide a concentrated area of heating and a relatively large value of resistance at the transition temperature; first circuit means for connecting said main winding across a source of electric power; second circuit means for connecting said starting winding, said capacitor, and said mass of material in series across said source in a manner so that both of said windings are initially energized and said mass of material including said neck portion is heated by the current flowing therethrough to reach the transition temperature after a preselected interval in order to substantially reduce the energization of said starting winding; and including heat sink means for cooling said mass of material upon deenergization of said motor.