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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.
There are several reasons for using the "Voltage boost" function:
● Magnetization build-up of an induction motor at n = 0 rpm
● Establishing a torque at n = 0 rpm, e.g. in order to hold a load
● Generation of a breakaway, acceleration or braking torque
● Compensation of ohmic losses in the windings and feeder cables
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.
Enclosed Drives
Operating Instructions, 12/2018, A5E36652151A
Setpoint channel and closed-loop control
7.3 V/f (V/Hz) control
451
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