Magnetic field analysis of linear tubular permanent magnet machine

The paper presents the analytical analysis of a new type of linear tubular permanent magnet machine which uses radially magnetized magnets. These magnets have been magnetized in stepped manner instead of uniform magnetization over the complete length. The stepped magnetized magnets improve the sinusoidal nature of the waveforms of radial flux density and induced emf by reducing their harmonics contents. An analytical solution for no load magnetic field has been presented. For optimal design of the machines, knowledge of magnetic flux density on the stator surface is necessary and this has been obtained from no load magnetic field analysis. This enables the no load induced emf directly. The analytical results have been compared with the FEM (Finite Elements Method) results and the two agree very closely.