A Method to Segregate Detent Force Components in Permanent-Magnet Flux-Switching Linear Machines

Detent force in permanent-magnet (PM) linear machines is caused by both end effect and slot effect. Segregation of the detent force into its end-effect and slot-effect components is helpful to better analysis and design. For conventional PM linear machines, the end-effect component of detent force can be easily calculated in a related slotless linear machine model, where the slot effect is eliminated. However, the slotless model is not applicable to permanent-magnet flux-switching (PMFS) linear machines, where the magnets and core teeth are set together on either a same stator or a same mover. This is because the PMFS machines cannot work at all without the teeth or slots. Therefore, a new method for segregating the detent force in the PMFS linear machines is proposed in this paper. Since a linear machine can be considered as a part of a particular rotary machine with large radius, and furthermore, cogging torque in the PM rotary machine is caused by the slot effect only, thereby the slot-effect component of the detent force in the PMFS linear machine can be calculated from the cogging torque in a related rotary machine, while the residual of the detent force is the end-effect component. Both finite element analysis (FEA) and experimental results show that the proposed method works well for the PMFS linear machines.