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Understand the basics of flux vector control for asynchronous motors to optimize performance with constant flux and torque. Learn how vector control improves speed precision and dynamic response.
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Flux vector control basics • The control of an asynchronous motor is made more difficult by the fact that the electrical parameters (current, voltage, flux) are alternating. • Furthermore, flux and torque are dependant upon current. • The principal of flux vector control consists in transforming the machine equations in such a fashion so as to:: • use variables as though the are continuous and no longer alternating, • simplify the equations in order to decouple the flux and torque variables. Flux r = K1 Id Torque C = K2s Iq • Flux is proportional to the Id component of current. • If the flux is constant, the torque is proportional to the Iq component of current. ATV71 M3 motor control V2
Asynchronous Motor DC Motor r r s Id Flux s I inductive I induced Torque Iq Flux vector control basics • Vector control allows the controller to separate the torque producing current and the flux producing current • This is analogous to a DC motor with separate excitation. • Flux is maintained constant and set at a point to obtain constant torque over the entire speed range. • The vector control has a speed estimation function that allows the full time correction of torque and flux. • Thus the performance is much better, for low speed torque, dynamic response, and speed precision compared to a scalar volts/Hertz law. ATV71 M3 motor control V2
Flux Vector Control U/FLaw Automatic Compensation (Rs and slip) Manual Compensation (U0 voltage at origin) C/Cn C/Cn 200 % 100% F hz F hz 1 3 FrS 5 10 FrS Flux vector control basics • Comparison of U/F and Vector control ATV71 M3 motor control V2