| 摘要 |
PURPOSE:To prevent a shortcircuit between phases at the wiring switching time by closing other electromagnetic contactor when one electromagnetic contactor of a Y-connection electromagnetic contactor and a delta-connection electromagnetic contactor is opened so that the phase currents of a 3-phase motor become zero, thereby closing the other contactor. CONSTITUTION:When an operation swtich 7 is closed, an overload and defective phase detection relay Ry1 becomes OFF, a relay X becomes ON, and the coil 2c of a Y-connection electromagnetic contactor 4 is excited. Then, the coil 2c of an auxiliary electromagnetic contactor 2 is excited, and a 3-phase motor 1 is started. When the prescribed period is elapsed, the contact T1 of a timer T is switched to ON side. When the phase current signals become zero value and an interphase shortcircuit preventive relay Ry2 becomes ON, the exciting coil 5c of a deltaconnection electromagnetic contactor 5 is excited. In this manner, the interphase shortcircuit at the wiring switching time can be prevented at the opening disable time of the contactor. |
