Inverters that undergo AC→DC→AC conversion are known as variable frequency power supplies, which differ from variable frequency controllers used for motor speed regulation and from standard AC voltage regulators. The primary function of a variable frequency power supply is to convert the existing AC grid power into a stable, pure sine wave power source at the desired frequency. Ideal AC power sources are characterized by stable frequency, stable voltage, zero internal resistance, and a pure sine wave voltage waveform (no distortion). Variable frequency power supplies are very close to ideal AC power sources, which is why more and more advanced and developed countries are using them as standard power supply sources to provide a good power supply environment for appliances and facilitate the objective evaluation of their technical performance.
