What is the difference between a variable frequency drive and an inverter?
An inverter changes DC power into AC power. You can purchase a small one that plugs into a power port in your automobile and converts 12VDC to single-phase 120VAC. An inverter is used in UPS systems to convert battery power to AC for your computer or server farm. Inverters are used with photovoltaic systems to convert solar power to utility AC power.
A variable frequency drive consists of three major subsystems - the converter, which takes AC utility power and rectifies it to DC; the filter, usually one or more large capacitors where this DC power is stored and smoothed; and the inverter which takes that fixed DC voltage and converts it into adjustable frequency, adjustable voltage output for the control of an induction or synchronous motor.
For some reason VFDs got tagged with the “inverter” nomenclature pretty early in their development.