It is commonly known as alternating current (AC), it include: voltage, current, frequency, the frequency can be divided into 50HZ (Hz) and 60HZ (Hz) ,voltage distribution from 100V to 240V. people in Taiwan use 60HZ/110V AC. The normal AC waveform is sine wave, but there are also some staircase waveform used to constitute similar to the sine wave, this kind of wave does not apply to motors or inductive load equipment.