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Abstract

The invention relates to a method for determining the stator flux of an asynchronous machine when a stator current (i.sub.2) and stator voltage (u.sub.s) of the asynchronous machine are measured and a short-circuit inductance (.sigma.L.sub.s), stator inductance (L.sub.s) and rotor time constant (.tau..sub.r) of the machine are assumed to be known, wherein the product of the stator current (i.sub.s) and a stator resistance estimate (R.sub.se) is determined, the obtained product is subtracted from the stator voltage (u.sub.s), and the obtained voltage difference is integrated with respect to time to obtain a first stator flux estimate (.psi..sub.se). In the invention, the method further comprises the steps of determining a second stator flux estimate (.psi..sub.se,id) on the basis of the stator voltage (u.sub.s), the stator current (i.sub.s), the short-circuit inductance (.sigma.L.sub.s), the stator inductance (L.sub.s), the rotor time constant (.tau..sub.r) and the stator resistance estimate (R.sub.se); determining a stator flux correction term (.DELTA..psi..sub.se) as a difference between the first stator flux estimate (.psi..sub.se) and the second stator flux estimate (.psi..sub.se,id), and summing the stator flux correction term (.DELTA..psi..sub.se) weighted by a constant coefficient (w) with said voltage difference.

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