| 摘要 |
PURPOSE:To reduce the magnetic sound of a motor on the basis of a PWM control by varying the hysteresis width of comparing means having hysteresis characteristic for comparing a current command signal with a current detection signal by an AC signal such as a triangular wave. CONSTITUTION:An induction motor 4 is driven by a PWM inverter 3 connected to a rectifier 1. A current command signal iu*, iv* formed of a speed command 14 and a signal of a speed detector 5 and iw* added by an adder 7, and a signal added by an adder 9 with the signals of current detectors 8U, 8V are applied to comparators 10U, 10V, 10W having hysteresis characteristic, an inverter 3 is controlled to be fired, and a triangular AC signal from a signal generator 12 is applied to a hysteresis width regulator 13 to regulate the hysteresis width of the comparators 10. Accordingly, the harmonic waves of the motor current are reduced, the magnetic sound of a motor can be largely reduced particularly at the low speed rotation time. |
