Advanced commissioning
7.5 Motor control
Converter with control units CU250D-2
Operating Instructions, 04/2015, FW V4.7.3, A5E34261542B AB
145
7.5.1.2
Selecting the U/f characteristic
Table 7- 16 U/f characteristics
Requirement
Application examples
Remark
Characteristic
Parameter
The required
torque is inde-
pendent of the
speed
Conveyor belts, roller
conveyors, chain con-
veyors, eccentric worm
pumps, compressors,
extruders, centrifuges,
agitators, mixers
-
Linear
p1300 = 0
The inverter equalizes the voltage drops
across the stator resistance. Recom-
mended for motors with a low power rat-
ing.
Precondition: You have set the motor data
according to the rating plate and have
performed the motor identification after
the basic commissioning.
Linear with Flux
Current Control
(FCC)
p1300 = 1
Additional information on U/f characteristics can be found in the parameter list and in the
function diagrams 6300 ff of the List Manual.
7.5.1.3
Optimizing motor starting
Setting the voltage boost for U/f control
After selection of the V/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, the V/f characteristic can be
raised at low speeds.
The inverter raises the voltage in ac-
cordance with the starting currents
p1310 … p1312.
The adjacent diagram shows the result-
ing voltage boost using a linear charac-
teristic as an example.
