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Which control technique is used for induction motor?
The purpose of the scalar control technique is to control the magnitude of the chosen quantities. For the Induction Motor (IM) the technique is used as Volts/Hertz constant. used in industrial variable speed drive system with vector control technology. This method requires a speed sensor for speed control.
What is a vector control VFD?
Vector control, also called field-oriented control (FOC), is a variable-frequency drive (VFD) control method in which the stator currents of a three-phase AC or brushless DC electric motor are identified as two orthogonal components that can be visualized with a vector.
What is scalar mode?
The main concept of Scalar control is to vary the voltage and frequency by the same ratio, thus maintaining the air-gap flux and hence the torque can be kept constant throughout the speed range. However, Scalar operation mode cannot control the torque with any degree of accuracy since the status of rotor is neglected.
Why VFD is used in motors?
Since the primary purpose of a VFD is precise SPEED CONTROL so that motor speeds can be ramped up and ramped down and the connected load can be maintained at the required speeds, which only utilizes the energy required.
How does an induction machine scalar control block work?
The Induction Machine Scalar Control block implements an induction machine scalar, that is V/f or V/Hz, control structure. The diagram shows the open-loop V/f control structure that the block implements. The Induction Machine Scalar Control block computes the magnitude of the stator voltage based on the reference frequency, , as:
How does scalar control work in an AC motor?
Scalar control (frequency control) is a control technique of a brushless AC motor, which is to keep the voltage/frequency ratio (V/Hz) constant throughout the full operating speed range, with control only the magnitude and frequency of the supply voltage.
How is the speed of an induction motor controlled?
In the V/Hz control, the speed of induction motor is controlled by the adjustable magnitude of stator voltages and frequency in such a way that the air gap flux is always maintained at the desired value at the steady-state.Sometimes this scheme is called the scalar control because it focuses only on the steady- state dynamic.
How is the magnetic field maintained in scalar control?
At the scalar control method, the induction motor speed is controlled by setting the voltage and frequency of the stator, so that the magnetic field in the gap is maintained at the desired value. To maintain a constant magnetic field in the gap, the V/Hz ratio must be constant at different speeds.