6.3 Holding brake (option)
Mode of operation of a permanent-magnet brake
The magnetic field of the permanent magnets results in a pulling force on the brake armature
disk. This means that in the no-current condition, the brake is closed and the motor shaft is
When 24 VDC rated voltage is connected to the brake, the solenoid – through which current
flows – establishes an opposing field. This neutralizes the force of the permanent magnets.
Permanent magnet brakes have a proportionally stiff connection to the motor rotor. This is
the reason that this brake is almost without any play.
Motors with integrated permanent-magnet holding brake cannot be subject to axial forces
at the shaft end! This applies when installing the system and during operation.
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, torsional backlash cannot be avoided. When the brake is closed,
the motor shaft can move by up to 1°.
Effect on vertical axes:
The motor brakes a vertical 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
The use of holding brakes with vertical axes must be carefully considered as a high danger
For motors with a spring-operated brake, the suitability of the brake based on the rotational
play must be verified.
For motors with spring-operated brakes, axial forces are permissible the same as for
versions without brake.
Configuration Manual, (PFK7S), Edition 12.2006, 6SN1197-0AD16-0BP1
Synchronous Motors 1FK7