Auxiliary switches, alarm switches and position signaling contacts
Front mounted motor operator
Motor operator actuation controlled via control cable
Motor operator actuation controlled via control cable and undervoltage release
This circuit is deployed in order to prevent no-load operation of the molded case circuit breaker. The contact of auxiliary contactor K1 prevents no-load operation when the undervoltage release "U<" is de-energized.
No-load operations subject the molded case circuit breaker to high stresses. If the undervoltage release is de-energized, auxiliary contactor K1 has not picked up. The contact in the ON circuit (control circuit) of the motor operator is thus not closed, that is, the molded case circuit breaker cannot be switched.
This auxiliary contactor is not necessary when the undervoltage release is supplied uninterrupted (e.g. pushbutton S01) from the same source as the motor operator itself (e.g. contact 3).