Method for continuous guidance of the rotor flux of an asynchronous motor which is supplied via a controllable invertor, including its operation in the weak flux region

摘要

It is intended to specify a method for the continuous guidance of the rotor flux, including operation in the weak flux region, when an asynchronous motor, which is supplied via a controllable invertor, is subject to current regulation based on the rotor flux. The method ensures that the rotor flux is guided continuously, smoothly and automatically over the nominal operating point, possibly utilising the entire invertor voltage with the dynamic response remaining good. To this end, the control error between a rotor flux reference variable ( PSI w) and the rotor flux controlled variable ( PSI ) is formed, on the one hand, and the control error between a drive level reference variable (aw) and the drive level controlled variable (a) of the invertor is formed, on the other hand. The two control errors ( DELTA PSI , DELTA a) are supplied to a minimum value selection device (6, 7), after being weighted with the desired proportional or integral gains (K PSI i, K PSI p, Kal, KaP). In order to adapt the control part to the dependency of the drive level control error ( DELTA a) on the rotation speed, said error is additionally multiplied by a variable which is proportional to the instantaneous flux ( PSI @). In the voltage control range (below the nominal operating point), the flux control error ( DELTA PSI ) is small in comparison with the drive level control error ( DELTA a), so that the drive level control error is not considered and the flux is actually controlled at a nominal value. In the weak flux region, the conditions are reversed, so that a change is made there from flux control to drive level control, .... Original abstract incomplete. IMAGE