| 摘要 |
PURPOSE:To operate an induction motor stably when the motor rotates at a low speed by a system wherein the induction motor is driven by means of a pulse width modulation type inverter while a limiter circuit clamped by means of a clamp value set circuit is mounted to the control system. CONSTITUTION:Instruction speed and actual speed are compared and supplied to a slip frequency instruction signal generator 7, and the output is added to the actual speed and given to a pulse width modulation circuit 16 through a V-F converter 10. Meanwhile, comparison signals are transmitted to a multiplying circuit 14 through a limiter circuit 13 clamped by means of a clamp value set circuit 22, and the output is composed with the output of the V-F converter 10 by means of a composite circuit 15. Consequently, operation in case of low speeds can be stabilized while output clamped in the case when load torque is large can be forwarded, thus softening impact force in case of the orientation of a machine tool, then optimally controlling an induction motor. |
