access icon free Analytical modelling of the effect of pole offset on the output parameters of BLDC motor

In this study, a new analytical model is provided to calculate the effect of the pole offset on the output parameters of brushless DC (BLDC) motor. The proposed model is based on the two-dimensional analysis model and the direct solution of Laplace and Cauchy–Poisson equations for the magnetic field in the air gap and the magnets area. In this model, radial and tangential components of the magnetisation vector are calculated. Effect of pole offset on the radial and tangential components of magnetisation vector is derived. It is shown that in the case of a motor with pole offset although the length of the magnet decreases at the edges of the pole, the effective air-gap length remains constant. This study proposed two coefficients to model the reduced thickness of the magnets at the edges of the poles. Therefore, the flux density is calculated in the air gap and motor magnets. Based on the proposed model, effect of pole offset on the cogging torque ripple and back-electromotive force is achieved. These results are compared with the results of finite element and experimental tests and accuracy of the model is presented.

Inspec keywords: Poisson equation; vectors; brushless DC motors; air gaps; machine insulation; magnetic flux; Laplace equations; finite element analysis

Other keywords: Laplace equation; back-electromotive force; cogging torque ripple; magnetisation vector calculation; pole offset effect; BLDC motor; finite element analysis; two-dimensional analysis model; flux density calculation; air gap; brushless DC motor; Cauchy-Poisson equation

Subjects: Finite element analysis; Linear algebra (numerical analysis); Differential equations (numerical analysis); d.c. machines

http://iet.metastore.ingenta.com/content/journals/10.1049/iet-epa.2017.0703
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