Abb Stromberg Drives Oy

Anders Hindsberg

Ilpo Ruohonen

The invention relates to a method of determining the estimate of the stator flux of an electric machine, comprising the determination of a stator flux estimate (.PHI..sub.sest) of the electric machine as a time integral of the difference between the voltage (u.sub.s) supplied to the stator and the product of the stator current (i.sub.s) and the stator resistance estimate (R.sub.sest), whereby the stator resistance estimate (R.sub.sest) of the electric machine is determined by correcting the initial value or another earlier value of the stator resistance on the basis of the stator current component (i.sub.d.sup.s, i.sub.d.sup..delta., i.sub.d.sup.r) parallel to the stator flux estimate (.PHI..sub.sest), the air gap flux estimate (.PHI..sub..delta.est) or the rotor flux estimate (.PHI..sub.rest). To be able to follow changes in the stator resistance of the electric machine in different operational conditions of the machine, said current component (i.sub.d.sup.s, i.sub.d.sup..delta., i.sub.d.sup.r) is compared with a set value (i.sub.d *) for the current component in question, the stator resistance estimate (R.sub.sest) being changed on the basis of the result of this comparison. (FIG. 4).

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Helsinki, Finland

Anders Hindsberg