| 摘要 |
PURPOSE:To prevent a frequency noise generated from a cage operating motor by controlling a circuit for inverting a DC converted from 3-phase AC by a signal from which harmonic waves of a current command signal calculated by a microcomputer are removed. CONSTITUTION:A DC rectified by a rectifier 2 and smoothed by a smoothing capacitor 3 from 3-phase AC is applied to an inverter 4 to generate a VVVF, and a motor 5 is driven by the VVVF. A microcomputer 15 inputs an external slip angle command signal 14 and a speed feedback signal 12a, generates current command signals 15a-15c, D/A-converts them by D/A converters 16A-16C, filters them via filters 31A-31C to remove harmonic waves to generate signals 31Aa-31Cc. Motor driving current signals 13Aa-13Cc detected by a CT and the signals 31Aa-31Cc are added by adders 17a-17Cc, amplified by amplifiers 18A-18C, and pulse-width modulated at switching elements of the inverter 4 through PWM controllers 19A-19C. Thus, a current command value becomes smooth waveform to be supplied to the inverter to prevent the frequency noise generated from a cage operating motor. |
