Function

Protective functions

The PTC thermistor triggering system disconnects a connected three-phase AC motor from the mains supply:

• at too high temperatures at the PTC thermistors inserted in the motor,
• after a short circuit in the PTC thermistor circuit,
• after a wire break in the PTC thermistor circuit,
• after the supply voltage fails in all three phases.

As soon as the protective system responds, the green operating indicator light on the underside of the unit goes out.

Once all causes of faults have been eliminated, the connected motor does not restart automatically. It can only be switched on again manually (restart interlock).