Comparative study of tubular partitioned stator permanent magnet machines

Permanent magnet (PM) linear machines have been extensively used for many linear motion applications since they can offer high efficiency, simple structure and high speed operation. In this paper, two novel PM tubular machines, i.e. partitioned stator interior permanent magnet (PS-IPM) and partitioned stator surface mounted permanent magnet (PS-SPM) tubular machines are proposed and optimised for maximum thrust force. Furthermore, the effect of main design parameters on the electromagnetic performances of two machines has been investigated. The influence of the magnet width to pole pitch ratio on the undesirable cogging force is also examined. It is found that the thrust force capability of the PS-IPM tubular machine is higher than that of the PS-SPM tubular machine, but the latter exhibits low cogging force. Both proposed machines show good thrust force capability, and in addition to this, the magnet demagnetisation risk is reduced since the magnets and the windings of the machines are separated from each other.