Triac control of a motor starter

摘要

The circuit (10) has a circuit for detecting a voltage representative of the voltage across a series connection of a positive temperature coefficient resistor (3) and a triac (T), and for comparing the detected voltage with respect to a threshold. A blocking circuit blocks a turning back on of the triac when the threshold exceeds. A circuit controlled by the blocking circuit controls the triac at the voltage zero. A resistive dividing bridge receives the voltage representative of a halfwave-rectified voltage across the series connection of the triac and the resistor. An independent claim is also included for a circuit for controlling an asynchronous motor.