1Summary Bertrand Guarinos STIE ATV71 M3 motor control V2

ATV71ATV71Flux vector control basicsFlux 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 = K2 s 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.

2Summary Bertrand Guarinos STIE ATV71 M3 motor control V2

ATV71ATV71Flux vector control basicsFlux 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.

DC Motor

I inductiveI induced

s

r

Id Flux

Torque

r

s

Iq

Asynchronous Motor

• 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.

3Summary Bertrand Guarinos STIE ATV71 M3 motor control V2

ATV71ATV71Flux vector control basicsFlux vector control basics

Comparison of U/F and Vector control

Flux Vector Control U/F Law

Automatic Compensation (Rs and slip)

Manual Compensation

(U0 voltage at origin)

C/Cn

FrS FrS5 101 3

100%

200 %

C/Cn

F hz F hz