Digital synthetic ripple modulator for point-of-load converters

The speaker comparatively investigates the unbalanced magnetic force (UMF) of external rotor machines having pole and slot numbers differing by one but no rotor eccentricity. The 8-pole/9-slot and 10-pole/9-slot machines are firstly optimised for maximum torque density by nonlinear FE analysis. Then, the UMF of both machines are analysed by both analytical model and linear finite-element model. It shows that the optimised 10-pole/9-slot machine has larger average torque than the 8-pole/9-slot machine for the same copper loss. However, the 10-pole/9-slot external rotor machine has significantly larger UMF than the 8-pole counterpart, which is opposite to the case of internal rotor machines.