Moeller - Connection examples, DM4 - Linking the overload relay into the control system

Linking the overload relay into the control system [t-head1-pg]

We recommend using an external overload relay instead of a motor-protective circuit-breaker with built-in overload relay. This allows controlled ramping down of the soft starter through the control section in the event of an overload.

Caution! [t-head3]

Connecting the motor directly to mains power can cause overvoltage and destruction of the soft starter’s semiconductors.

There are two options, which are shown in the following diagram:


	Emergency-Stop S1: Off S2: On Q21: Soft starters, enablr (E2 = 1 → enabled) The overload relay’s signalling contacts are incorporated in the On/Off circuit. In the event of a fault, the soft starter decelerates for the set ramp time and stops. The signalling contacts of the overload relay are linked into the enabling circuit. In the event of a fault, the soft starter’s output is immediately de-energized. The soft starter switches off but the mains contactor remains on. To de-energize the mains contactor as well, include a second contact of the overload relay in the On/Off circuit.

More information

With separate contactor and overload relay

Without mains contactor