Level of harmonics produced by variable frequency drive controller used in induction type water pump motor

Abstract

This study focuses specifically on the determination of electrical noise or harmonic level generated by the variable frequency drive controller in terms of its amplitude and frequency. The central area of concern is the effect of harmonics on the power quality of the electrical supply of Central Philippine University at the point of the pump-motor equipment. Based on the results of the tests, the harmonics of the supply voltage was 2.25%. Running the 5-HP motor directly produced a lower harmonics of 2.10%. When the controller was used to run the motor, the controller in itself produced a significant level of harmonics of 8.42%which interferes with nearby electronic appliances within a very close proximity. A substantial part of the harmonics produced by the controller is filtered from going out of the device itself, so that the harmonic level at the source terminal was about 3.93 %, showing an increase of 1.83% compared to running the motor without the use of the controller. The value is within the acceptable limits of 5% for electronic circuits and systems, but not acceptable for medical and other related highly sensitive instruments, which require a total harmonic distortion (THD) of not more than 3%.