| 摘要 |
PURPOSE:To alleviate a mechanical shock at switching time by detecting the speed when the speed is switched from high to low speeds, and turning ON a power source of a low speed operation when the speed decreases to the vicinity of the speed at low speed operation time. CONSTITUTION:When high speed operation switching units 2, 3 are opened, a pole change motor 4 is naturally decelerated. The speed of decelerated state of the motor 4 is monitored by a rotation detector 8 via the remaining voltage of the motor 4, the fact that the speed arrives at the vicinity of the speed at low speed operation time of the motor 4 is detected, and the second switching unit 1 for low speed operation is closed. Thus, the difference between the speed of the motor 4 during natural deceleration and the low speed operation speed is almost 0, thereby alleviating the mechanical shock at switching time. |
