Patent ID: 6037742
Filing Date: 2000-03-14
Classification: H02P

Abstract:
Method for indirect field-oriented control of an induction motor by means of a frequency converter incorporating control mean, the method comprising the steps of:(a) measuring rotor position of the motor,(b) calculating a slip frequency,(c) determining a transformation angle (.delta.) from the measured rotor position (.THETA.r) and the calculated slip frequency (.omega.s) by summation,(d) making a first correction of the transformation angle (.delta.) based on a fixed dead time,(e) measuring motor current,(f) determining a field-oriented voltage reference value (U.sub.sdref) given by the control means,(g) estimating a field-orientated actual voltage value (U.sub.sdpred) employing the magnetizing component of the measured motor current and taking into consideration a voltage drop proportional to the measured current,(h) calculating a voltage difference (e.sub.d) between the voltage reference value (U.sub.sdref) and the actual voltage value U.sub.sdpred),(i) determining an error angle (.epsilon.) between a voltage reference vector (U.sub.so) and an actual voltage vector (U.sub.'so) employing the voltage difference (e.sub.d), assuming an approximately equal amplitude and a known phase angle of the voltage reference vector (U.sub.so) and the actual voltage vector (U'.sub.so),(j) making a second correction of the transformation angle (.delta.) employing the determined error angle (.epsilon.).