VFD is generally a power control device that converts a power frequency power supply into another frequency by using the on-off function of power semiconductor devices. The main circuit of the variable frequency drive can be roughly divided into two categories: the voltage type is a frequency converter that converts the DC of the voltage source into an AC, the filter of the DC circuit is a capacitor; the current type is a frequency converter that converts the DC of the current source into an AC, its DC loop filter is inductance.The following ATO will introduce you how to set 120V to 220V VFD panel