V/F Control - Siemens SINAMICS G120 CU240B-2 Operating Instructions Manual

Examples of typical applications in which vector control is used:
● Hoisting gear and vertical conveyors
● Winders
● Extruders
It is not permissible to use vector control in the following cases:
● If the motor is too small in comparison to the inverter (the rated motor power may not be
● If several motors are connected to one inverter
● If a power contactor is used between the inverter and motor and is opened while the
● If the maximum motor speed exceeds the following values:
Pole number of the motor
Maximum motor speed [rpm]
7.6.1

V/f control

V/f control sets the voltage at the motor terminals on the basis of the specified speed
setpoint. The relationship between the speed setpoint and stator voltage is calculated using
characteristic curves. The inverter provides the two most important characteristics (linear
and square-law). User-defined characteristic curves are also supported.
V/f control is not a high-precision method of controling the speed of the motor. The speed
setpoint and the speed of the motor shaft are always slightly different. The deviation
depends on the motor load. If the connected motor is loaded with the rated torque, the motor
speed is below the speed setpoint by the amount of the rated slip. If the load is driving the
motor (i.e. the motor is operating as a generator), the motor speed is above the speed
setpoint.
Inverter with CU240B-2 and CU240E-2 Control Units
Operating Instructions, 07/2010, FW 4.3.2, A5E02299792B AA
less than one quarter of the rated inverter power)
motor is powered up
Inverter pulse frequency 2 kHz
2-pole 4-pole 6-pole
9960 4980 3320
Functions
7.6 Motor control
4 kHz and higher
2-pole 4-pole 6-pole
14400 7200 4800
169