18.7 Functions of Field-Orientated Control
The field-orientated control systems are based on a cascade control and the calcula-
tion of a complex machine model. The various control functions can be supplemented
by special functions specific to the application.
18.7.1 Motor Chopper
The field-orientated control systems contain the function for adapted implementation
of the generator energy into heat in the connected three-phase machine. This en-
ables the realization of dynamic speed changes at minimum system
and speed behavior of the drive system is not influenced by the parameterized brak-
ing behavior. The parameter
Trigger threshold 507 of the DC link voltage defines the
switch-on threshold of the motor chopper function.
507 Trigger threshold
1000.0 V
The parameter Trigger threshold 507 is to be set in such a way that it is between
the maximum DC link voltage which the mains can generate and the maximum ad-
missible DC link voltage of the frequency inverter.
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If the parameter Trigger threshold 507 is set larger than the maximum admissible
DC link voltage, the motor chopper cannot become active;
the motor chopper is
switched off.
If the set Trigger threshold 507 is smaller than the maximum DC link voltage the
mains can generate, error message F0706 (chapter "Error Messages") is displayed
when the frequency inverter is switched on.
The motor chopper function only works if activated via voltage Controller Operation
Mode
670. See chapter 17.2 “Voltage controller”.
For synchronous motors (Configuration 30 = 5xx), the motor chopper function is de-
activated to prevent damages to the motor. The other functions of the voltage control-
ler are not affected by this.
Please note that by default the Motor chopper Trigger Threshold 507 and the Trigger
Threshold
506
are set up with different values. Check, that the two thresholds are set
up fittingly for your application.
06/13 Operating Instructions ACU 251
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