Magnetic field analysis and optimal design of DC permanent magnet coreless disc machine

The magnetic field in a DC permanent magnet coreless disc machine is studied in depth by using different methods, such as three dimensional finite element method (3DFEM), two dimensional finite element method (2DFEM) and magnetic circuit method (MCM) based on an analytical solution. For optimization, the cases for different magnet dimensions, airgap lengths and configurations are investigated in detail. Numerical results show that if the field is provided by the ferrite magnets, the ratio of magnet thickness to airgap length should be greater than 3 and the distance from magnet to stator wall or the width of the magnetism-free channels between two adjacent poles should be greater than 6 mm. Moreover, both 2DFEM and MCM are feasible for general optimal design purpose focusing on practicality and time saving.>