Temperature protection relay PMM/T series

for electric motorsDIN rail

The Thermistor protector trip relay monitors the temperature of a motor using the PTC sensor (positive temperature coefficient resistor) or thermostat (TK) switch built in to the motor winding. Relay contacts can be used to disconnect the supply to the motor should it overheat. LEDs indicate mains on and fault status. Basic Parameters • Selectable PTC or TK modes • Reset function • Selectable memory function for latching • Power on LED (green) Operation The Thermistor protector trip relay operates by de-energising a relay and illuminating a red LED when the thermistor detects a critical temperature condition. Should the motor overheat and the PTC resistance go above the 3.3kOhms, the relays de-energise. The contacts remain de-energised until the PTC resistance falls to 1.8kOhms. The selectable memory switch allows the option of latching the relay and the red LED stays illuminated until the reset button is pressed or triggered via the external reset switch. Any number of thermistors may be used in series connection providing the resistance at normal working temperature is less than 1500 ohms.