Motor Control - Siemens SINAMICS G120 Operating Instructions Manual

8.6

Motor control

For induction motors, there are two different open-loop control or closed-loop control
techniques:
● Open-loop control with V/f-characteristic (V/f control)
● Field-oriented control (vector control)
Criteria for selecting either V/f control or vector control
V/f control is perfectly suitable for almost any application in which the speed of induction
motors is to be changed. Examples of typical applications for V/f control include:
● Pumps
● Fans
● Compressors
● Horizontal conveyors
Commissioning vector control takes more time than when commissioning V/f control. When
compared to V/f control, vector control offers the following advantages:
● The speed is more stable for motor load changes.
● Shorter accelerating times when the setpoint changes.
● Acceleration and braking are possible with an adjustable maximum torque.
● Improved protection of the motor and the driven machine as a result of the adjustable
● The full torque is possible at standstill.
● Torque control is only possible with vector control.
Examples of typical applications in which vector control is used:
● Hoisting gear and vertical conveyors
● Winders
● Extruders
SINAMICS G120C Inverter
Operating Instructions, 01/2011, FW 4.4, A5E02999804A AB
torque limiting.
Functions
8.6 Motor control
183