| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to accelerate an induction motor with good efficiency with the rotational angular velocity of an induction motor coincident quickly with the angular velocity command of an inverter by a method, wherein, when a torque component becomes smaller than a synchronous turning-on permission current, a mode is changed over to an acceleration mode and a steady operation in a constant-speed mode is started when the torque component reaches a rated current. SOLUTION: A mode comparator 11-11 outputs an angular velocity instruction ω1. At this time, the angular velocity command ω1 contains a first-order lag element so as to become small, and it is brought close to an angular velocity at which an induction motor is turned. That is to say, the angular velocity command ω1 is brought close, from a rated angular velocity ωdef, to an angular velocity at which a rotor at the induction motor is turned, and it coincides nearly with the angular velocity. Then, the torque current component of the induction motor is reduced. Then, at a point of time when the torque current component becomes smaller than a synchronous turning-on permission current, a mode is changed over to an acceleration mode. Then, when a transient angular velocity ωtrn which is computed by a synchronous turning-on computing unit 11-13 and which is given to the induction motor is raised up to the rated angular velocity ωdef, the mode enters a steady mode. |
