Commissioning
5.3 Preparing for commissioning
SINAMICS G115D distributed drive
Operating Instructions, 12/2020, FW V4.7 SP13, A5E48681219B-002
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5.3.3
Selecting U/f control or speed control
For reluctance motors, sensorless vector control (SLVC) is mandatory (p1300 = 20).
For asynchronous motors (2KJ8 asynchronous motors excluded), there are two different
open-loop control or closed-loop control techniques:
•
U/f control (calculation of the motor voltage using a characteristic curve)
•
Closed-loop speed control (i.e. field-oriented control or vector control)
For 2KJ8 asynchronous motors,
sensorless vector control (SLVC) is recommended (p1300 = 20).
Criteria for selecting either U/f control or speed control
In many applications, U/f control suffices to change the speed of asynchronous motors.
Examples of typical applications for U/f control include:
•
Horizontal conveyors
•
Pumps
•
Fans
•
Compressors
When compared to U/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.
•
Torque control is only possible with vector control.
Examples of typical applications in which speed control is used:
•
Hoisting gear and vertical conveyors
•
Winders
•
Extruders
It is not permissible to use speed control in the following cases:
•
If the motor is too small in comparison to the converter (the rated motor power must not
be less than one quarter of the rated converter power).
•
When you operate several motors on one converter.
•
When the maximum motor (4-pole) speed exceeds the following values:
Converter pulse frequency
2 kHz
4 kHz and higher
Maximum motor speed
4980 rpm
7200 rpm