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