| 摘要 |
PURPOSE:To obtain rising characteristic having good response even when a load is desired to be rapidly risen by supplying a high voltage to a motor when the operating speed of an operating member is fast. CONSTITUTION:When a foot pedal 5 is pressed slower than the set value in an inverter 1 for driving a 3-phase induction motor 6 of a sewing machine 3, the output of a comparator 10 becomes L level, the switch of a winding converter 11 is not operated, and the motor windings become Y-connection. When the pedal 5 is, on the contrary, pressed faster than the set value, the output of the comparator 10 changes to H level, the switch of the converter 11 is operated so that the windings become delta-connection. Thus, the voltages applied to the windings increases to 3<1/2> times of that of the Y-connection. On the other hand, the output torque of the motor increases proportionally to the square of the voltage applied to the winding. Accordingly, the output torque of three times of that is obtained as compared with the conventional Y-connection, thereby providing good response in the rising characteristic of the machine 3. |
