Step down transformers provide low voltage AC power for lighting, instruments and other circuits that use alternating current at a lower voltage.

降压变压器低压AC电源提供照明，仪器仪表和其他使用交流电在一个较低的电压的电路。

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BUS protection PANEL, a module (black box) containing electrical circuits for control and protection of electrical alternating current supply to the airplane.

汇流条防护板，黑匣子式的组件，内含控制和保护飞机交流电源的电路。

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Further, the current quadrilateral and admittance quadrilateral, as well as their similarity to the power quadrilateral in non-sinusoidal alternating-current circuits were derived.

由功率四边形进一步确立了非正弦交流电路中的电流四边形和导纳四边形，以及它们和功率四边形的相似关系。

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