| 摘要 |
PURPOSE:To prevent an abnormal high speed condition at a starting process due to the unbalance of load torque by a mechanism wherein the number of revolution of a wound-rotor induction motor is detected, a contactor is operated when the value exceeds the set value, and a secondary resistor is short-circuited. CONSTITUTION:A secondary resistro 9 is mounted at the secondary side of a motor 1 while contactors MC1-MC3 are installed which short-circuit the resistance value of the resistor 9 in the reducing direction when starting. The number of revolution of the motor 1 is detected by means of a revolution number detector 11 such as a speed generator, the contactor MC3 is energized through a judging circuit 12 and a drive circuit 13 when the value exceeds the set value, and the resistance value of the secondary resistor 9 is made to zero. Thereby, an abnormal high speed condition is avoided on the basis of the unbalance of load torque at a starting process in the case when driving a lifting gear, etc. lifting and lowering a carrier 6 through a chain gear 3 and a chain 4 by means of the motor 1, and the revolution can be controlled to a synchronous speed extent. |
