Lenze i950 Series, Manual

Page: 252 / 500

13.5.2 Short-circuit braking
The control modes for synchronous motors provide the opportunity to use "short-circuit brak-
ing" for braking.
The effect of short-circuit braking on the deceleration behaviour depends on the motor prop-
erties, the effective cable length, the load inertia and the initial speed value (starting point).
Primarily, short-circuit braking serves to transform a part of the kinetic energy into heat
energy which unburdens external brake assemblies and limit position dampers.
NOTICE
In some constellations 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" function, the braking effect is considerably lower.
▶
Prevention: tbd
Preconditions
If short-circuit braking shall be used as the only deceleration means, it is recommended that
the feasibility is previously verified by means of tests. For this purpose, short-circuit braking
can be triggered in the application via bit 6 in the Lenze control word 0x2830 . The oscilloscope
function of the engineering tool (e.g. »EASY Starter«) serves to record the following important
parameters:
•
Actual velocity 0x606C
•
Phase current U, V, W ...
Details
The short-circuit current adjusts itself freely in accordance with the motor volt-
age (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 differs, a rating based
on the currently possible parameters (max. speed, max. motor current, field
weakening, etc.) is required!
The function 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.
Configuring the motor control
Parameterisable motor functions
Short-circuit braking
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