HEIDENHAIN TNC 410 M Technical Manual page 456

7 – 34
PE power
cable
Due to the inductance of the holding brakes, a voltage peak that may exceed
1000 V occurs when the exciting current is switched off.
A protective circuit is not necessary if the holding brakes are controlled via the
inverters, since the internal electronic switches limit the voltage.
To avoid the voltage peak that occurs when controlling the holding brakes by
relay, use a protective circuit with an R varistor (recommended model: Q69-
X3022).
The following circuitry is suggested for the protective circuit of the brake:
HEIDENHAIN Technical Manual for Inverter Systems and Motors
Shield for
holding
brake
Shield
Strain relief