STARTING DEVICE FOR MOTOR

PURPOSE:To make a starting current uniform by a method wherein a motor terminal voltage is impressed on a magnet coil, a magnetostrictive element displaced by an exciting current of the coil is used as an actuator and a variable resistor connected thereto is inserted in series into an armature circuit. CONSTITUTION:An actuator A has a construction wherein magnetostrictive elements 2a to 2c and 1a to 1c of cylindrical type PTC and NTC which expand or contract in the axial direction when a magnetic field is applied are fitted in each other alternately and coaxially and a magnet coil 6 is disposed on the outer circumference. When a motor is started and an armature voltage Ea is generated, an exciting current flows through the magnet coil 6, each of the magnetostrictive elements of PTC and NTC is made to expand or contract in accordance with the strength of the magnetic field, an output shaft 3 is pushed down by the total amount of displacement of the elements, and a movable contact 13 is made to slide toward an electrode 12b through the intermediary of an insulative rod 22. Since a resistance 11, i.e., a start resistance Rs, lessens gradually in proportion to the amount of the slide, a rush current is not generated and an armature current is kept at a prescribed value.