Setpoint channel and closed-loop control
7.3 V/f control
Drive converter cabinet units
Operating Instructions, 07/07, A5E00288214A
269
7.3.1
Voltage boost
Description
With low output frequencies, the V/f characteristics yield only a small output voltage.
With low frequencies, too, the ohmic resistance of the stator windings has an effect and can
no longer be ignored vis-à-vis the machine reactance. With low frequencies, therefore, the
magnetic flux is no longer proportional to the magnetization current or the V/f ratio.
The output voltage may, however, be too low to:
●
Magnetize the induction motor.
●
Maintain the load.
●
Compensate for the voltage losses (ohmic losses in the winding resistors) in the system.
●
Induce a breakaway / accelerating / braking torque.
You can choose whether the voltage boost is to be active permanently (p1310) or only
during acceleration (p1311).
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Figure 7-5
Voltage boost total
Note
The voltage boost affects all V/f characteristics (p1300) from 0 to 6.
NOTICE
If the voltage boost value is too high, this can result in a thermal overload of the motor
winding.
