| 摘要 |
PURPOSE:To suitably detect an overload even by a hysteresis motor in which an ultrafine slip occurs by opening a contactor during the operation. CONSTITUTION:When a contactor 2 is opened sometimes during an operation and an H motor 9a even slips ultrafinely, a large current flows through individual current transformers 5a since the counterelectromotive force of the motor 9a is different in frequency from the other H motors 9b-9z. Accordingly, a malfunction signal is output from the output terminal 14a of a comparator 12. At this time, small amounts of currents flows also through the transformers 5b-5z of the motors 9b-9z, but the current is one divided by the number of the motors. Thus, a malfunction signal is not generated, but a malfunction can be detected only for the malfunctioned motor. |
