Setpoint channel and closed-loop control
7.3 V/f control
Inverter chassis units
Operating Instructions, 07/2016, A5E00331449A
331
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). In addition, a one-off voltage boost in the first power up after
pulse enable can be set via p1312.
Figure 7-6 Voltage boost total
Note
Voltage boost effect
The voltage boost affects all V/f characteristics (p1300) from 0 to 7.
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