A variable-frequency drive is a device used in a drive system consisting of the following three main sub-systems: AC motor, main drive controller assembly, and drive/operator interface.: 210–211. AC motor. The AC electric motor used in a VFD system is usually a three-phase induction motor. ELIMINATING HARMONICS PROBLEMS CAUSED BY VFDs Presented by: John Houdek [email protected] AGENDA Assumptions Impact of facility loads on distribution system power quality Alternative techniques for mitigating harmonics Performance expectations for alternative methods Best practice Variable Frequency VFD5 Base-Emitter Signal Input Pins DC Link Positive Terminal C 1 DC Link Negative Terminal E 2 Phase Output Terminal E 1C 2 Module Mounting Holes Heat Sink on Module Back -Plane Module Schematic Diagram Variable Frequency Drive (VFD) Output Module Shown below is a typical Medium Voltage VFD transistorized output module.