Functions
7.6 Motor control
Inverter with CU240B-2 and CU240E-2 Control Units
168 Operating Instructions, 07/2010, FW 4.3.2, A5E02299792B AA
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The quick-stop function (OFF3) has a separate ramp-down time, which is set with P1135.
Note
If the ramp-up/down times are too short, the motor accelerates/decelerates with the
maximum possible torque and the set times will be exceeded.
Extended ramp-function generator
In the extended ramp-function generator, the acceleration process can be made "softer"
using initial and final rounding via parameters p1130 … p1134. Here, the ramp-up and ramp-
down times of the motor are increased by the rounding times.
Rounding does not affect the ramp-down time in the event of a quick stop (OFF3).
For more information, see the List Manual (the parameter list and function diagram 3070).
7.6 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
torque limiting.
● The full torque is possible at standstill.
● Torque control is only possible with vector control.
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