Harmonics in variable speed fan systems

Abstract

The characteristics of harmonics generated by variable speed fan systems used for ventilation of agricultural buildings are reported. The fan system is controlled with a variable speed, triac-based fan controller and is fitted with a three-bladed, 30 degrees pitch polypropylene propeller. A test is conducted to evaluate voltage and current harmonics produced as a result of the triac's presence in the fan system circuit. The triac introduced harmonics into the current waveform which reduced the motor efficiency. The fan system is not a significant source of voltage harmonics for the utility. Current harmonics are at significant levels with the third current harmonic being the highest at 100% of the fundamental.<>