LioneHutz. The illustration shows the harmonics generated by the VFD in the creation of the PWM waveform controlling the motor speed. The increase in harmonic current as the load reduces, maybe not what you would expect, but is exactly what happens in practice. The illustration was taken from a...
The Total Harmonic Distortion (Ithd) is considerably higher when the motor is running at lower speeds than when at 100% load. ie. much higher currents in the 5th and 7th harmonic components creating heat.
