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4.3.2
Brake types
Brakes with different principles of operation are used:
•
•
Both of the brake types operate according to the closed-circuit principle.
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
held.
When 24 V DC 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.
Caution
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 for hanging 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 care-
fully 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.
1FK7 Synchronous Motors
Configuration Manual (PFK7), 10/2005 Edition, 6SN1197-0AD06-0BP1
Permanent-magnet brake
Spring-operated brake
Motor Components (Options)
Holding brake
4-11
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