Vector Control - Siemens SINAMICS S120 Function Manual
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Also See for SINAMICS S120:
- Function manual (1094 pages) ,
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Operating Modes
Vector control
3.2
Vector control
Compared with vector V/f control, vector control offers the following benefits:
S Stability vis-à-vis load and setpoint changes
S Short rise times with setpoint changes (--> better command behavior)
S Short settling times with load changes (--> better disturbance characteristic)
S Acceleration and braking are possible with maximum available torque
S Motor protection due to variable torque limitation in motor and regenerative
mode
S Drive and braking torque controlled independently of the speed
S Maximum breakaway torque possible at speed 0
Vector control can be used with or without an encoder.
The following criteria indicate when an encoder is required:
S High speed accuracy is required
S High dynamic response requirements
-- Better command behavior
-- Better disturbance characteristic
S Torque control in a range greater than 01:10:00 AM is required
S Allows a defined and/or variable torque for speeds below approx. 10% of the
rated motor frequency (p0310) to be maintained.
With regard to setpoint input, vector control is divided into:
S Closed-loop speed control
S Torque/current control (in short: torque control)
3.2.1
Vector control without encoder (SLVC)
Notice
Vector control without an encoder can only be carried out with induction motors.
In vector control without an encoder (SLVC), the position of the flux and actual
speed must be determined via the electric motor model. The model is buffered by
the incoming currents and voltages. At low frequencies (approx. 0 Hz), the model
cannot determine the speed. For this reason and due to uncertainties in the model
parameters or inaccurate measurements, the system is switched from closed-loop
to open-loop operation in this range.
3-108
© Siemens AG, 2005. All rights reserved
SINAMICS S120 Function Manual, 06/05 Edition
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