| 摘要 |
PROBLEM TO BE SOLVED: To realize long life without generating damage of a cooling fan, by applying a contactless contactor limiting the starting torque of a motor to the starter of an induction motor for driving the cooling fan. SOLUTION: A three-phase AC power source is supplied to an induction motor 14 through an MCCB breaker 11, a soft starter 12 and an overcurrent relay 13. A contactless contactor S using a thyristor or the like and a mechanical contactor M are connected with the soft starter 12. Just after the starting, a current flows through a semiconductor contactor S of the soft starter 12, and the current value gradually increases. When the value reaches finally a stationary value, i.e., the rating value of an induction motor 14, the mechanical contactor M turns to the close state, and the starting is finished. Thereby long life can be realized without damaging a cooling fan at all, while a general-purpose induction motor 14 and the cooling fan which are advantageous to cost are used. |
