| 摘要 |
PROBLEM TO BE SOLVED: To obtain a method and an apparatus, in which a power consumption is reduced, and in which the operation time of a warming-up operation is shortened. SOLUTION: The frequency of a primary current at an induction motor is set to be high to such an extent that a slip becomes a value close to one and that a rotor is not vibrated even when the direction of rotation of a rotating magnetic field is changed alternately. A current instruction is set in such a way that the primary current which is sufficient to positively heat a stator by a copper loss and an iron loss flows. The direction of rotation of the rotating magnetic field is changed in such a way that the rotor is held in a substantially stopped state, and a warming-up operation is executed so as to be shifted to an ordinary operation after the warming-up operation has been finished. |
