Siemens SIMODRIVE 611 Configuration Manual page 58

Motor Components
5.4 Holding brake
Mode of operation of a spring-operated brake
For a spring-operated brake, instead of the magnetic field of a permanent magnet, the force
of a spring is used.
In order for a spring-operated brake to operate, the brake armature disk must be able to
axially move. Therefore, rotational play cannot be avoided. When the brake is closed, the
motor shaft can move by up to 1°.
Effect for hanging (suspended axes):
The motor brakes a hanging (suspended) axis electrically. If the brake is applied and the
power is then disconnected, it is possible that the load could continue to move the motor
shaft. In this case, the maximum possible motion corresponds to the above mentioned play
in the gear meshing. The motion is appropriately stepped-up or stepped-down using a
mounted gearbox.
Danger
Applications involving holding brakes for hanging/suspended axes must be especially
carefully investigated as these represent a high potential hazard.
For motors with spring-operated brake, it must be carefully checked that the brake is suitable
due to the rotational play.
For motors with spring-operated brakes, axial forces are permissible the same as for
versions without brake.
Protective circuitry for the brake
Caution
In order to avoid overvoltages when shutting down and the possible negative impact on the
plant or system environment, a protective circuit must be integrated into the brake feeder
cable (refer to Fig. "Recommended circuit for the external power supply with protective
circuit").
If protective circuitry is not used, voltage peaks up to 1000 V can occur in the millisecond
range. Brake solenoid, switching contacts and electronic components could be destroyed.
Sensitive electronic components (e.g. logic components) can even be damaged as a result
of a lower switch-off voltage. The power limits (e.g. ratings) of the components used should
be carefully observed.
5-8
Configuration Manual, (PJAL), 11.2005 Edition, 6SN1 197-0AD07-0BP4
General Section for Synchronous Motors