Selecting The U/F Characteristic - Siemens SINAMICS G120D Operating Instructions Manual

The value of the output voltage at the rated motor frequency also depends on the following
variables:
● Ratio between the inverter size and the motor size
● Line voltage
● Line impedance
● Actual motor torque
The maximum possible output voltage as a function of the input voltage is provided in the
technical data.
6.5.1.2

Selecting the U/f characteristic

Table 6- 25 Linear and parabolic characteristics
Requirement Application examples
The required Conveyor belts, roller
torque is inde- conveyors, chain
pendent of the conveyors, eccentric
speed worm pumps, com-
pressors, extruders,
centrifuges, agitators,
mixers
The required Centrifugal pumps,
torque increases radial fans, axial fans
with the speed
Table 6- 26 Characteristics for special applications
Requirement
Applications with a low
dynamic response and
constant speed
The inverter must keep
the motor speed con-
stant under all circum-
stances.
Freely adjustable U/f
characteristic
U/f characteristic with
independent voltage
setpoint
Additional information on U/f characteristics can be found in the parameter list and in the
function diagrams 6300 ff of the List Manual.
Converter with control units CU240D-2
Operating Instructions, 07/2016, FW V4.7 SP6, A5E34262100B AD
Technical data (Page 309)
Remark
-
The inverter equalizes the voltage drops across
the stator resistance. Recommended for motors
less than 7.5 kW.
Precondition: You have set the motor data accord-
ing to the rating plate and have performed the
motor identification after quick commissioning.
Lower losses in the motor and inverter than for a
linear characteristic.
Application examples Remark
Centrifugal pumps, The ECO mode results in additional energy
radial fans, axial fans saving when compared to the parabolic
characteristic.
If the speed setpoint is reached and re-
mains unchanged for 5 seconds, the in-
verter again reduces its output voltage.
Drives in the textile When the maximum current limit is
sector reached, the inverter only reduces the
stator voltage but not the speed.
- -
- The interrelationship between the frequen-
cy and voltage is not calculated in the in-
verter, but is specified by the user.
Advanced commissioning
6.5 Motor control
Characteristic Parameter
Linear p1300 = 0
Linear with p1300 = 1
Flux Current
Control (FCC)
Parabolic p1300 = 2
Characteristic Parameter
ECO mode p1300 = 4
or
p1300 = 7
Precise fre- p1300 = 5
quency char- or
acteristic p1300 = 6
Adjustable p1300 = 3
characteristic
Independent p1300 =
voltage set- 19
point
157