| 摘要 |
PURPOSE:To avoid an unstable closed operating condition by isolating a motor or the like from a power system before the rotational speed of a pump or the like lowers to a value below a predetermined level and guide vanes or the like are fully closed during stop of operation of the pump or the like. CONSTITUTION:The main shaft of a motor or the like 1 is directly coupled to a pump or the like 2, and the rotational speed of the motor or the like 1 is detected by a rotational speed detector 3 and is delivered to an operation control device 4 which determines optimum energizing current value and rotational speed, and delivers control signals to a variable speed control device 5 and a governor 6, As a result, the speed of the motor or the like 1 is controlled while guide vanes 7 are opened and closed, and the output of the pump or the like 2 is controlled accordingly. In this phase, during stop of operation of the pump or the like 2 the motor or the like 1 is isolated from the power system before the rotational speed of the pump or the like 2 lowers to a value below a predetermined level and the guide vanes 7 or the like are fully closed.
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