| 摘要 |
PURPOSE:To prevent a hydraulic relay from erroneously operating by enabling to switch between a commercial power source and an AC variable speed inverter power source, and controlling to gradually regulate the output frequency of the inverter power source, thereby suppressing the hydraulic change to the minimum. CONSTITUTION:An AC variable speed inverter power source is turned ON when an oil pump is started or stopped to regulate an oil flow. A switching contactor 88T is connected with the inverter power source 4 side when the pump is started to reduce the output frequency, thereby starting the pump. Since, i.e., inverter power source 4 can be obtained in a wide frequency range, an oil pump motor of an induction motor is rotated at the speed proportional to the frequency. Since the hydraulic change due to the oil flow is gradually converged, the output frequency of the power source 4 is raised to match the converting state to gradually increase the oil flow, and the converting state to gradually increase the oil flow, and the power source is eventually switched by the contactor 88T to a commercial power source 1 when approaching substantially to the rated frequency range. |
