Lenze i950

13.5.2 Short-circuit braking
The control modes for synchronous motors provide the opportunity to use "short-circuit brak-
ing" f
or braking.
The eect of short-circuit braking on the deceleraon behaviour depends on the motor prop-
eres, the eecve cable length, the load inera and the inial speed value (starng point).
Primarily, short-circuit braking serves to transform a part of the kinec energy into heat
energy which unburdens external brake assemblies and limit posion dampers.
NOTICE
In some
constellaons it is not possible to decelerate the motor speed of a synchronous
motor to zero by means of "short-circuit braking"!
Compared to the "quick stop" funcon, the braking eect is considerably lower.
▶
Prevenon: tbd
Precondions
If short-circuit braking shall be used as the only deceleraon means, it is recommended that
the f
easibility is previously veried by means of tests. For this purpose, short-circuit braking
can be triggered in the applicaon via bit 6 in the Lenze control word 0x2830. The oscilloscope
funcon of the engineering tool (e.g. »EASY Starter«) serves to record the following important
parameters:
•
Actual v
elocity 0x606C
•
Phase current U, V, W ...
Details
The short-circuit current adjusts itself freely in accordance with the motor volt-
ag
e (kE * speed) and the internal resistance of the system. Thus, it is absolutely
necessary that the ampacity of the servo inverter is based on the maximum
expected short-circuit current. Guide value: I
max_device
(3 s) ≥ 1.5 * Imax_motor
(according to data sheet / catalog) In case the assignment diers, a rang based
on the currently possible parameters (max. speed, max. motor current, eld
weakening, etc.) is required!
The
funcon can be used as follows:
1.
"Short-circuit braking" can be parameterised via bit 6 in the Lenze control word 0x2830 if
•
the braking energy cannot be converted into heat in a brake resistor.
•
e.g. an error has been detected in the encoder system which does not permit a braking
via quick stop.
2.
"Short-circuit braking" can be parameterised as a response to minor faults.
•
Due to an encoder error, for instance, a quick stop might not be possible anymore.
Conguring the motor control
P
arameterisable motor funcons
Short-circuit braking
252