| 摘要 |
PURPOSE:To prevent free falling of a load in a crane or the like, by a method wherein a power source is provided separately from a control power source, and the length of initial current rising time of the control winding of a saturable reactor is eliminated. CONSTITUTION:In a control circuit having control power source A-C and controlling the winding-up or winding-down of a load W, the control of the control power source B is performed when the load W is wound down, and an electromagnetic brake MB is used at the stop state. In the case of a crane, however, the stop torque of only the electromagnetic brake MB is not sufficient and the rotational force in U-direction must be temporarily given to an induction motor IM. However, if the control of the control power source B is stopped and then the control of the control power source A is started, lag exists in rising of control current by the control power source A. Consequently, the power source C is installed separately from the control power source A, thereby a definite current corresponding to the initial current is normally given to the control winding of reactors X1, X2, X3 at winding-up side. |
