Brake control, fail safe circuits

Question:
How can the brake's application be ensured in case of a 9300, which is supplied by 24 V and which has an open circuit in terminal 39 (GND)?

Answer:
An open circuit of the 9300 servo's earth connection (terminal 39) can have the effect that the brake output switches to High signal (brake ventilation) due to the loss of the reference potential and independent from the internal control. Consequently, the brake is ventilated, although it should be applied. In case of hoist applications without independent monitoring this could lead to a sagging of the hoist.

The fail safe circuits of the brake control can be increased by using two digital outputs and one external interconnection. The two digital outputs must be switched inversely to each other. This interconnection corresponds to safety class 5 (1-channel) according to DIN 19250. It does not replace the redundancy required in case of possible injury or bigger damage to property. This interconnection only ensures that the brake engages when there is no connection to earth.

External connection of the brake control: