SCHUTZSCHALTER

1. A protective circuit to prevent the thermal overloading of the winding of an alternating-current electric motor (1) having a triac (2) which is connected in series with the motor winding and interrupts the motor circuit in the event of inadmissible heating of the motor winding, and connected in parallel with which is the series connection of a PTC resistor (4) and of a dropping resistor (5) and the gate of which is connected to the junction of these two resistors (4, 5), and, when the motor is switched off as a result of inadmissible heating, the PTC resistor (4) has a greatly altered resistance value as a result of which the ratio of the voltage division at these resistors (4, 5) is then shifted so that the gate voltage tapped off between the resistors (4, 5) is no longer sufficient to fire the triac (2), characterized in that introduced into the gate feed line of the triac (2) or into the motor (1)-triac(2) circuit between the triac (2) and the series connection of the resistors (4, 5) is a thermal circuit-breaker (3) which can be heated by the motor winding and opens its breaker contact if the temperature of the motor winding exceeds its maximum permissible value.