| 摘要 |
PURPOSE:To improve rotational performance in a medium-speed or high-speed zone without using a larger induction motor, by reducing the number of the coils of the stator of the induction motor connected to an inverter, when the induction motor is moved into the high-speed rotational-zone. CONSTITUTION:At the time of starting an induction motor 6, respective contactors 8a, 8b, 8c are on terminals S2, and the output of an inverter 5 is applied to all of respective coils 9a, 9b, 9c. When the rotation of the induction motor 6 is increased and an allowance between stalling torque and running torque is reduced, then the output of change-over command is directed to a change-over command circuit 10 from a controller 11, and the respective contactors 8a, 8b, 8c are switched to terminals S1. Accordingly, in a high speed zone, a magnetic flux quantity is increased by the component of the number of the turns of released coils,and the stalling torque is also increased, and so by the increased component of the stalling torque, a constant-voltage rotational- zone can be extended to the high speed side, and the performance can be improved. |
