Design of permanent magnet flat linear motors for standstill applications

The authors examine planar linear permanent magnet motors and consider their operation at standstill. A method of finite element analysis (FEA) is used in which the use of several space phase-shifted force profiles accounts for the machine skew. The origin of the cogging forces, namely tooth and finite stator length effects, is explained. Results are given from a large experiment rig. It is shown that both cogging and electromagnetic forces compare well with the FEA. The authors conclude with a design survey using simple magnetic circuit theory considering the application of both NdFeB and ferrite magnets. Points on the graphs are validated by the FEA.