shows the simulation result when there is no
harmonic back-EMF compensation. Due to the existence of
the harmonic back-EMF, the control of the PM motor can not
guaranty an ideal state. As simulation result shows that current
ripples can be found both with the d- and q- axis currents. The
real time current ripples are strongly related to the coupled
rotor flux linkage in the stator windings, so the shifting
frequency of the current ripples varies as motor speed changes.