| 摘要 |
An AC voltage reduction system and method providing highly efficient reduction of utility voltage with minimal electromagnetic interference is provided. The systems and methods may also be used to improve overall facility power factor. The AC voltage provided to a load, such as a group of lighting ballasts connected on a single circuit, is reduced by a controllable switch coupled in parallel with a capacitor between the AC source and the load. The switch is controlled to turn-on when the voltage across the capacitor is very close to zero and turn-off prior to the next zero-crossing of the line current. The turn-off time is selected in an open loop configuration independently of a measured characteristic of load voltage or watts. In order to provide proper operation of gas discharge lighting, the switch is initially turned off just in advance of the AC source current zero-crossing. To reduce the voltage and provide related power savings the turn-off time is gradually moved to a time more prior to the zero-crossing.
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