| 摘要 |
PURPOSE:To improve reliability of a supply water system by considering a cause of abnormality provided in a peripheral device of an inverter so that operation can be continued, in the case that a pressure of supply water is decreased by abnormality of the supply water system despite that the inverter itself is normal. CONSTITUTION:A main contact MC1a is opened by any cause to interrupt a feed of power to an electric motor 6, during inverter operation, and to decrease its rotational speed, and when a pressure of supply water detected by a water pressure sensor 5 is decreased to a preset value or less, a signal Sd is output. Then after the predetermined time, an electromagnetic contactor in a water failure preventing circuit 3 is actuated to close its main contact MC3a and also locking the electromagnetic contactor to a control up-opening condition by a lock signal So to directly drive the electric motor 6 by a commercial power supply ACL. Even after the predetermined time, when the pressure of supply water is continued to decrease, the electromagnetic contactor of the water failure preventing circuit 3 is again inoperative to open its main contact MC3a, and a supply water system is stopped by stopping the electric motor 6. |
