I have designed a 9-level inverter which was used to derive a single-phase induction motor. when measuring the THD, I found that the current THD is higher than the voltage THD as shown in Figures below. Current THD is 11.6% and voltage THD is 8.8%. Is there any reason why the current THD is higher than the voltage THD? Thanks a lot
Because the current or motion of electrons are responsible for power transfer from source to load. And switching of thyristors mainly affect the magnitude and direction of current
Thank you, Jyotsana,
In my situation, the current is not smooth. It contains harmonics. The THD percentage is high 11.6% compared with 8.8% for the voltage harmonics?
Is there any reason?
Thanks again
@Wail Ali Ali Saleh,
What comes to my mind is in this situation there could be two sources for the current THD. Either you have a some sort of switching device between your multi-level inverter and the induction motor or the motor core is saturated.
The former is less likely because a switching device would have produced high order harmonic distortions but in the FFT image that you posted the main contributor is the 3rd order harmonic, which narrows down my guess to the latter option: "saturated motor core".
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