| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that conventionally the center point potential becomes unbalanced, when an over current is generated right after the recovery to the steady PWM pattern, and the motor makes unstable run and damages capacitor and the switch element. SOLUTION: The PWM inverter consists of an overcurrent detector 1, an alarm signal generator 2, a carrier generator 3, a common PWM pattern 9, a current limiter pattern generator 10, a neutral pattern generator 11, a PWM pattern selector 12, and a motor driver 17. A peak and trough generator 4 is provided to form a peak pulse, to output a pulse at the peak of the carrier and a trough pulse to output a pulse at the bottom of the carrier, and a carrier differentiation pulse generator is also provided to output 1 at the rise of the carrier and 0 at the fall of the carrier. When an overcurrent is generated, the carrier is checked as to whether it is rising or falling. Based on this check, the inverter is switched from the normal PWM control synchronizing with the selected pulse signals to the overcurrent PWM control, and is then recovered to the normal PWM control after one cycle of the carrier. |
