| 摘要 |
PURPOSE:To eliminate over excitation due to overvoltage or step-out due to undervoltage through a start control means for achieving acceleration in low frequency region by performing current controlled voltage control at the time of starting. CONSTITUTION:A rated current setter 8 sets the rated current of a synchronous motor 3 and a current detector 9 detects DC current when a current is fed from an inverter body 2 to the motor 3. A converted voltage from a current- voltage converter 14 is switched through a switch 15 to the output voltage of a frequency-voltage converter 5 and employed as a voltage control signal for a PWM unit 6. A comparator 16 compares a differential current from a subtractor 10 with a set value and a counter 17 begins to count the clock based on the detection output from the comparator 16 and switching is made from the converter 14 to the converter 5 upon reaching a predetermined count. Consequently, the motor is started with a limited current until the counter 17 counts up, thus preventing over excitation due to overvoltage or step-out due to undervoltage. |
