| 摘要 |
PURPOSE:To keep off any abnormal wear of lining and so on by connecting an impressed voltage lowering means, which controls a semiconductor switching element and lowers a voltage being impressed on a coil when a current detector detects a momentary sudden decrease during increment of a coil current, to an interval between the current detector and the semiconductor switching element. CONSTITUTION:When an elevator starting command is inputted, a motor 2 is connected to a three-phase power source 7 via a motor control circuit 5 and an electromagnetic contactor's contact 6 and simultaneously another electromagnetic contactor's contact 21 is closed so that a current gets flowing in a coil 14. At a point of time, a power transistor 24 is conducted. In consequence, this coil current increases, whereby attraction of a plunger 10 overcomes pressing force of a spring 12, thus this plunger 10 operates. If so, since the coil current is suddenly changed, transistor output comes to pulselike output, and these pulse are amplified by an amplifier 37 and inputted into the transistor 24, so that this transistor 24 repeates ON, OFF, restricting the current flowing in the coil 14, thus a brake is kept to an open state. |
