| 摘要 |
PURPOSE:To control accurately the DC voltage fed to a motor in the case of DC braking, to stabilize the braking torque of the motor, to suppress fluctuation of the time to be elapsed before positive stoppage of the motor, and further, to make the braking time of the motor short, by outputting the DC voltage in PWM mode. CONSTITUTION:A switch 21 is interlocked with a switch 17 for switching a PAM frequency control circuit 19 and a PWM control circuit 20 between normal operation, and DC operation. In the normal operation, both the switches 17, 21 are connected respectively with sides (a). When a stopping command is inputted to an inverter, the speed of a motor is reduced, and both the switches 17, 21 are connected respectively with sides (b) just before the motor is stopped. Hereupon, considered is the case wherein the DC voltage command of 10 volt is outputted from a voltage command generator 16 during DC operation and the DC voltage between output terminals U, W of the inverter is set at 10 volt. In this case, from the PWM control circuit to the switch 17, outputted is the control signal which makes the ON-time of the duty cycle of the switch 17 short by 10%, and from the PWM control circuit to the switches 8, 10, 12, outputted are the control signals whose phases are opposed to the ones of the switches 7, 9, 11. |
