time:2023-02-07 13:56:27Views:
The control of three-phase asynchronous motors is much more complicated than that of DC motors, because the current, voltage, induced electromotive force, magnetic flux, etc. of the stator and rotor are all alternating.
However, the stator winding of a three-phase asynchronous motor is a symmetrical three-phase winding, and the current generated after applying a symmetrical three-phase voltage is a symmetrical three-phase current. The magnetic field generated in the windings and the air gap of the motor is sinusoidally distributed along the rotating magnetic field in a constant amplitude space determined by the frequency and the number of pole pairs of the winding.
The electric potential induced by the rotor winding in the air gap magnetic field and the resulting induced current are still symmetrical and sinusoidal, proportional to the magnetic flux and velocity of the air gap. The resulting electromagnetic torque is determined by the air gap flux and rotor current.
These relationships are similar to those of a DC motor.
In addition, when standing on the rotor, the magnetic field generated by the stator and the rotor is also a static magnetic field, which is distributed in a sinusoidal shape along the space.
Therefore, the models of DC motors and asynchronous motors are basically similar. The same applies to synchronous motors. Comparison of VIF Control and Magnetic Flux Vector Control
VF control The control model is simple, no motor model is needed, only (rated voltage, rated frequency) and origin voltage are needed.
Flux vector control needs to know the motor nameplate parameters and adjust by yourself to determine the motor model required for flux vector control.
Through magnetic flux vector control, slip compensation and low-frequency RI compensation can be performed according to load conditions to obtain faster accuracy, wider speed range, faster dynamic response and excellent low-speed performance. I can do it.
VF control can only compensate fixed low-frequency voltage in the low-speed section, and can only compensate inaccurate manual slip according to the magnitude of the current during operation, so as to realize static and dynamic driving performance and magnetic flux vector control. possible. There are some gaps.
However, VF control is suitable for motors with special parameters, parallel motors, mismatched motors, relatively special loads, or further reduction of flux for energy saving.
