Harmonic Distortion and Variable Frequency Drives

Harmonic Distortion is a measure of the amount of deviation from a pure sinusoidal wave form that can be caused by a non-linear load.

Purpose of VFD: Control, Speed & Torque.

What is a VFD?
Microprocessor Controller Power Converter
Converts input Power (ex: 480V, 3ph to DC) - Rectifier - Input Section Cleans up DC Bus Voltage - DC Link
Switching Section outputs to motor - Inverter
Drive faults:
Overcurrent Fault-Drive has sensed too much current in its output.
Overvoltage fault-The drive has sensed an overvoltage condition in its DC bus
Under voltage fault-The drive has sensed the line voltage or its power supply voltage is too low
Low harmoincs VFDs have Insulated Gate Bipolar Transistors (IGBT)
IGBT inverter that goes to over temperature that causes a VFD tripping.
IGBT may be over heated during operating.