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

摘要

In the motor starting system disclosed herein, the start winding of an induction motor is connected in series with a mass of material which has a resistance characteristic having a positive temperature coefficient and a sharply defined transition temperature above which the material's resistance increases sharply. When power is applied to the motor, the initially low resistance of the mass allows the start winding to be substantially energized. After a predetermined delay, the mass of material heats to its transition temperature and the resulting increase in resistance substantially reduces the energization of the start winding thereby controlling the timing of the start cycle. The increased resistance of the mass upon heating also functions to protect the start winding from damage caused by prolonged overloads since increase current flow produces an increase in the resistance of the mass.