Classification by Input Voltage Level
Frequency converters can be classified into low-voltage frequency converters and high-voltage frequency converters based on their input voltage level. Common low-voltage frequency converters in China include single-phase 220 V frequency converters, three-phase 220 V frequency converters, and three-phase 380 V frequency converters. Common high-voltage frequency converters include 6 kV and 10 kV transformers, and the control method is generally based on high-low-high frequency conversion or high-high frequency conversion.
Classification by Frequency Conversion Method
Frequency converters are classified into AC-AC type frequency converters and AC-DC-AC type frequency converters based on the frequency conversion method. AC-AC type frequency converters can directly convert industrial frequency AC power into AC power with controllable frequency and voltage, hence they are called direct frequency converters. AC-DC-AC type frequency converters first convert industrial frequency AC power into DC power through a rectifier, and then convert the DC power into AC power with adjustable frequency and voltage, hence they are also called indirect frequency converters.
Classification by the Nature of the DC Power Source
In AC-DC-AC type frequency converters, the nature of the DC power source during the conversion of the main circuit power into DC power is used to classify them into voltage-source frequency converters and current-source frequency converters.