Phase control circuit for protection of a motor against thermal overload

摘要

Thermal overload of a motor is avoided by measuring temperature and, when a limit temperature is exceeded, reducing the phase "window" within each power cycle during which the motor is energized. The limit temperature is sensed by a temperature sensor which is warmed either by heat conduction through a cooling body or by an air stream from the motor. The overload protection apparatus requires no measuring resistance in the load circuit.