Mechanical installation
Holding brake (option)
Installation
5
23
Lenze • BA 33.0006 • 5.1
5.4 Holding brake (option)
Important notes
As an option, the motors can be fitted with a brake. The installation of brakes (in or on
the motor) increases the length of the motor.
Note!
The brakes used are not fail-safe because interference factors which
cannot be influenced (e.g. oil ingress) may lead to a reduction in torque.
The brakes are used as holding brakes and serve to hold the axes at standstill or in the
deenergised state.
Emergency stops at higher speeds are possible but high switching energy increases
wear on the friction surfaces and the hub, 26).
The spring-applied brakes work on the basis of the closed-circuit principle, i.e. the brake
is closed in the deenergised state. The brakes for DC supply can be fed with a
bridge-rectified DC voltage (bridge rectifier) or with a smoothed DC voltage. The
permissible voltage tolerance is ±10 %.
If long motor supply cables are used, pay attention to the ohmic voltage drop along the
cable and compensate for it with a higher voltage at the input end of the cable.
The following applies to Lenze system cables:
U*= U
B
+
0.08 Ω
m
⋅ L ⋅ I
B
U* [V] Resulting supply voltage
U
B
[V] Rated voltage of the brake
l[m] Cable length
I
B
[A] Rated current of the brake
Stop!
If no suitable voltage (incorrect value, incorrect polarity) is applied to the
brake, the brake will be applied and can be overheated a nd destroyed by
the motor continuing to rotate.
The shortest operating times of the brakes are achieved by DC switching of the voltage
and an external suppressor circuit (varistor or spark suppressor). Without suppressor
circuit, the operating times may increase. A varistor/spark suppressor limits the
breakingvoltage peaks. It mustbe ensured that thepowerlimitofthe suppressor circuit
is not exceeded. This limit depends on the brake current, brake voltage, disengagement
time and the switching operations per time unit.
Furthermore the suppressor circuit is necessary for interference suppression and for
increasing the servicelife ofthe relaycontacts (external, not integrated into the motor).
Please refer to the catalogue for servo motors for detailed information
about holding brakes.
Note!
The brake cannot be readjusted. When the wear limit is reached, the
brake has to be replaced.
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