| 摘要 |
PROBLEM TO BE SOLVED: To attain the maximum power saving effect within a short period of time when an input voltage is higher and control the switching of the unnecessary tapping when an input voltage is low by switching the tap to attain the maximum power saving effect and also controlling the switching of tapping in the time band where an input voltage drops. SOLUTION: An input voltage Vi is applied to any one of the taps T1 to Tn of a transformer and a secondary side voltage V2 of the transformer 1 is varied to control an output voltage Vo by opening an electromagnetic contactor MC2 and closing an electromagnetic contactor MC1 and an of the semiconductor switches SSR1 to SSRn. A voltage control apparatus compares previously stored voltage variation patterns of a day, shortens a supervising time of an input voltage and selects and changes over the tap T1 to Tn for attaining the maximum power saving effect in the time band where rise of an input voltage is assumed and also normalizes the supervising time of the input voltage and controls change-over of the taps T1 to Tn in the time band where drop of input voltage is assumed.
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