| 摘要 |
PURPOSE:To continue to operate all load motors by obtaining a motor speed by a counterelectromotive force at recovery time when a power source is interrupted while one of a plurality of power sources is stopped due to maintenance or defect to decide the operating frequency of an inverter. CONSTITUTION:If a commercial power source is interrupted when a power source 1-3 is defective and is stopped, and a hysteresis motor 3 is operated by the remaining two power sources 1-1, 1-2, the motor 3 is disconnection from the power sources 1-1, 1-2, and naturally decelerated. When recovered, the rotating speed of the motor 3 is measured by a principle of a counterelectromotive force method by a controller 8 and an instrument transformer 7, and the power sources 1-1, 1-2 are restarted in the same frequency as it. Accordingly, the power sources 1-1, 1-2 becomes no load in this state. Then, a contactor 4 is closed to connect the motor 3 which is decelerated naturally with the power source 1-1, 1-2. |
