Analysis of 3-D Effects in Segmented Cylindrical Quasi-Halbach Magnet Arrays

To improve the performance of permanent magnet (PM) machines, quasi-Halbach PM arrays are used to increase the magnetic loading in these machines. In tubular PM actuators, these arrays are often approximated using segmented magnets resulting in a 3-D magnetic field effect. This paper describes the results of this segmentation obtained from an analytical model. The influence of the number of segments on the magnetic flux density in the air gap is investigated for several actuator dimensions. Furthermore, the effect of this segmentation on the mean value of the radial component of the flux density over the circumference of the cylindrical air gap is analyzed and a 2-D definition of this effect is given. A general rule is presented as a table showing the decrease of the magnetic field as function of the design parameters.