Cogging Torque Analysis in a Series Hybrid Variable Flux Machine Using Lumped Magnetic Circuits

This work tries to compute cogging torque in a 36-slot 6-pole SVFM where the higher coercive force N48SH magnet is in series with the lower coercive force AlNiCo9 magnet. A lumped parameter model of the SVFM is developed based on the magnetic flux lines in a slot-less machine obtained using the finite element analysis (FEA) method. The air gap flux density in the slot-less 6-pole SVFM is calculated using the developed lumped magnetic circuit model at different magnetization levels of the AlNiCo9 magnet. The error between the analytical and FEA results of air gap flux density is less than 4% at lower magnetization levels. By utilizing the air gap flux density in an equivalent slot-less machine and the relative air gap permeance function, the cogging torque of the 36-slot 6-pole SVFM is computed and compared to the analytical results at different magnetization levels of the AlNiCo9 magnet.