PROBLEM TO BE SOLVED: To attain high accurate control of speed and torque, by performing correction of an arithmetic speed by speed estimation based on reactive power without using primary resistance. SOLUTION: In a voltage current outer product means 11, a primary vector 11 of an output of a current detector 2 and a primary voltage vector VI of an output of a voltage detector 3 are input, reactive power Q1 is output by arithmetic operation. In a magnetic flux current outer product means 12, a primary magnetic flux vector 1 of an output of a primary magnetic flux arithmetic device 8 and a primary current vector are input, reactive power Q2 is output by arithmetic operation. In an arithmetic speed corrector 13, these reactive powers Q1, Q2 and the arithmetic speed m of the output of a speed arithmetic device 7' are input, then an arithmetic speed m' is estimated by arithmetic operation. Thus, in a secondary magnetic flux arithmetic means 6', in lieu of the arithmetic speed m, the arithmetic speed m', which is the estimated speed of the output of the arithmetic speed corrector 13, is used, a secondary magnetic flux vector 2 can be calculated.
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