Harmonics can be eliminated by using passive LC filters or it can newly eliminated by active filters. Where active filter are more effective in eliminating the harmonics as it is based on generating harmonics equal in magnitude and antiphase and injecting these harmonics in the load.

Best wishes

Dear Peter

I agree with Prof. Abdelhalim Zekry

Regards

Thanks alot for all your answers, kindly I think my question is not clear enough, I mean why most of papers care for current harmonic cancellation for dual motors or 6-phase machines.... but generally no one consider or care for these current harmonics in a normal 3-phase machine ? so why ?

Current harmonic are caused by non-linear load for example when an rectifier is connected to such system making it's current waveform quite complex also depending on the interaction of the component with other components present in the system. And a lot of scientific search in going on on how to reduce this pollution of current harmonics if possible eliminate it.

Hello Peter Azer

[edit] The 5th and 7th harmonics are present in both machine topologies, but the additional degrees of freedom that a six-phase machine offer allows compensating these harmonics without affecting much the field and torque control. In fact, by controlling the so-called "x & y" current components, torque production capability should improve.

On the other hand, compensating these harmonic components in three-phase machines might require the use of more complex control techniques, and it might affect the control in d-q-reference frames.

I think that questions is about temporal harmonics or currents harmonics.