| 摘要 |
PURPOSE:To continue an operation without fail without temporarily stopping an induction motor even if a power source is momentarily interrupted by gradually raising only a voltage from zero while the frequency of an AC output from an inverter is the same value as that at the time of generating an insufficient voltage. CONSTITUTION:If a voltage of an AC power source 2 is insufficient such as a predetermined value or less, for example, power interruption, this power interruption is detected by an instrument transformer 21 and an insufficient voltage detector 22 to open a closed contact 23. Accordingly, an acceleration/ deceleration calculator 12 is reset. A contact 23 is closed simultaneously upon recovery of the power interruption, and the calculator 12 so raises its output as to arrive at a set value from a speed setter 11. Therefore, a transistor inverter 5 gradually rises from zero only at a voltage while the frequency remains as a previous value, and an induction motor 6 restarts an operation upon establishment of its excitation. |
