Relationship between harmonic currents and harmonic magneto-motive forces in multi-phase induction machines

Analysis) of the performance of multi-phase induction machines with non-sinusoidal currents in their stator windings requires knowledge of the relationship between the harmonic currents and the corresponding harmonic magneto-motive forces (MMF's). Fourier analysis was used to resolve the non-sinusoidal current into the fundamental component and a series of harmonic components to calculate the resulting MMF's. The relationship between the harmonic currents and the composite harmonic MMF's was derived to yield a generalized expression relating the harmonic currents and the harmonic MMF's. The analysis illustrates that the relationship for multi-phase induction machines differs from that for three-phase induction machines. A twelve-phase induction generator, which produces the 5th harmonic voltage instead of the desired fundamental voltage, is used as an example to verify the analytical results and to develop a method to significantly reduce the 5th harmonic voltage.