Many drives need a holding brake with an emergency stop function for safety reasons or to meet process requirements.

The permanent magnet single-surface brakes used on the SIMOTICS S‑1FT7/S‑1FK7 motors function according to the closed‑circuit principle. The magnetic field of the permanentmagnet exerts a tension on the brake anchor plate, i.e. in a condition of zero current, the brake is closed and the motor shaft thereby stopped. When the rated voltage of 24 V DC ± 10 % is applied to the brake, current flows through the coil and produces a counter‑field that cancels the pull of the permanent‑magnet, causing the brake to release.

In the event of an emergency stop or power outage, approximately 2000 braking operations can be performed with maximum switched energy without causing excessive wear on the holding brake (condition: maximum external moment of inertia = moment of inertia of motor and n_max type‑specific).

The holding brake is not an operational or safety brake.

In order to avoid switching overvoltages and any related effects on the plant environment, the brake cables must be connected externally with a varistor. The connection is made via the power connector or the terminal box.

When connected to the SINAMICS S120 drive system, this overvoltage protection is provided by the SINAMICS system.