Ac Alternating current (ac) is electric current that alternates between a positive maximum value and a negative maximum value at a characteristic frequency, usually 50 or 60 cycles per second (Hertz).

交流交流是指电流在正负最大值之间以特定的频率变动，通常频率为50或60赫兹。

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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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Inverters and microinverters convert the direct current (DC) power produced by solar panels into alternating current (AC) used in homes and businesses.

FORBES: Solar Microinverter Maker Enphase Gets A Boost In Distribution Deal With Siemens

Since 2005, the company has stood out in the fast-moving LED industry with an innovation that allows LEDs to be powered by alternating current, or AC, rather than requiring a transformer that turns AC into direct current.

WSJ: Seoul Semiconductor's LED-Lighted Path