Operating Instructions ACU
19.7 Functions of field-oriented control
The field-oriented control systems are based on a cascade control and the calculation of a complex
machine model. The various control functions can be supplemented by special functions specific to
the application.
19.7.1 Motor chopper
The field-oriented control systems contain the function for adapted implementation of the generator
energy into heat in the connected three-phase machine. This enables the realization of dynamic
speed changes at minimum system costs. The torque and speed behavior of the drive system is not
influenced by the parameterized braking behavior. The parameter Trigger Threshold 507 of the DC
link voltage defines the switch-on threshold of the motor chopper function.
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 admissible 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 (see Chapter 21.1.1 "21.1.1") is displayed when the frequency
inverter is switched on.
The motor chopper function will only work if it was activated via the voltage controllers
Operation Mode 670 . See Chapter 18.2 "18.2".
For synchronous motors (Configuration 30=5xx or 6xx), the motor chopper feature is
deactivated to prevent the motor from being damaged. The other functions of the
voltage controller are not affected by this.
Note that, by default, the motor chopper Trigger Threshold 507 and brake chopper
Trigger Threshold 506 are set to different values. When using both functions make
sure the set thresholds are suitable for the application.
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