Mechanical installation
Spring−applied brakes
24
Lenze ¯ BA 33.0008 ¯ 5.0
5.5
Spring−applied brakes
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, (
¶
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 %.
In case of long motor cables the voltage drop must be checked due to increasing
conductor resistance and compensated for by higher input voltage if necessary.
The following applies to Lenze system cables:
U *
+
U
B
)
ƪ
0.08
W
m
@
L
@
I
B
ƫ
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 and 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
breaking voltage peaks. It must be ensured that the power limit of the 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 service life of the relay contacts (external, not integrated into the motor).
