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Advanced commissioning
6.7 Motor control
6.7.2.2
Optimizing motor starting
Overview
After selection of the U/f characteristic, no further settings are required in most applications.
In the following circumstances, the motor cannot accelerate to its speed setpoint after it has
been switched on:
● Load moment of inertia too high
● Load torque too large
● Ramp-up time p1120 too short
To improve the starting behavior of the motor, a voltage boost can be set for the U/f
characteristic at low speeds.
Precondition
The ramp-up time of the ramp-function generator is, depending on the motor rated power, 1 s
(< 1 kW) ... 10 s (> 10 kW).
Function description
Setting the voltage boost for U/f control
The converter boosts the voltage corresponding to the starting currents p1310 ... p1312.
Figure 6-70
Increase parameter values p1310 ... p1312 in steps of ≤ 5 %. Excessively high values in
p1310 ... p1312 can cause the motor to overheat and switch off (trip) the converter due to
overcurrent.
If message A07409 appears, it is not permissible that you further increase the value of any of
the parameters.
Procedure
1. Switch on the motor with a setpoint of a few revolutions per minute.
2. Check whether the motor rotates smoothly.
382
The resulting voltage boost using a linear characteristic as example
Operating Instructions, 06/2019, FW V1.01, A5E44751209B AC
SINAMICS G120X converter
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