The effect of harmonic on load and the concept of applying phase shifting transformer to reduce harmonics generated by non-linear loads

Harmonic effect is caused by non linier loads such as variable frequency drives, lighting and computers. VFD uses power electronics to vary the frequency of input power to the motor. While PWM allows for nearly sinusoidal currents to be applied to a motor load, the diode rectifier of the VFD takes square wave current pulses out of the ac grid, creating harmonic distortion in the power line voltage. Harmonics can cause a many of problems ranging from poor power factor and motor failures, to overload transformers and conductors. Therefore it becomes necessary to reduce high magnitude harmonics to get a clean and efficient power. One of the most effective ways to eliminate harmonics is to use a technique known as “phase shifting”. This paper represents the effect of harmonic on load and its mitigation technique for a non linier load by observing the behavior of VFD.