| 摘要 |
PROBLEM TO BE SOLVED: To perform speed control by accurately estimating the speed of an induction machine, without having to use speed detectors where an electric motor is mounted. SOLUTION: The secondary voltage of an induction motor 2 is detected by voltage detectors 6a and 6b, the rotary speed of an induction machine is estimated by a speed estimating arithmetic unit 21 according to a secondary voltage signal, and a self-quenching type element 4 is turned on or off, to control the output current of a forward converter 3 according to the deviation between the estimation speed signal and its command value, thus controlling the speed of the induction motor. |
