Difference Between Variable Speed Drive (VSD) And Variable Frequency Drive (VFD)

A Variable Frequency Drive (VFD): is a drive that works on changing the frequency of an AC motor, it always refers and can be used with AC drives only.

A Variable Speed Drive (VSD): is a drive that works on changing the speed of a motor by varying the voltage supplied to it regardless of its type, it always refers to either AC Drives or DC Drives.