Research On A Tubular No-Overlap Type Transverse-Flux Permanent-Magnet Linear Machine

This article proposed a novel tubular transverse flux permanent magnet linear machine(TFPLM), which is for a free-piston energy converter in series hybrid electric vehicles (HEV). The first, this machine can meet the demands of free-piston energy converter which are low velocity and high thrust. The second, combined with combustion engine,this machine can provide benefits in high efficiency and environmental protection. The third, the novel structure solves the problems of low power factor and complex process which current transverse flux permanent machines (TFPMs) face.First of all, the leakage flux of Z type TFPLM is investigated by three-dimensional finite-element method (3D FEM). On that basis, a novel tubular TFPLM is proposed, it includes two structures: three phases in the axial direction and three phases in the circumference direction. Taking the structure which has three phases in the axial direction for example, the operating principle is explained.Secondly, to simplify the computational complexity and save computing time, the simplified 3D finite-element models of two structures are establishied; Beacause leakage factor is an important parameter for TFPM, so the axial thickness of stator core with long teeth and pole arc coefficient is optimized and determined primarily to get the lowest leakage factor; The significant effect of staggered stator teeth on the reduction of the armature-flux axial-leakage is verified; What's more, by comparing the no-load characteristics and load characteristics of the two structures, results prove that the structure with three phases in the axial direction has greater advantage.Thirdly, based on the analysis of thrust fluctuations and the guiding relationship of power factor and force density to structure parameters, the axial thickness of stator core with long teeth and the pole arc coefficient is optimized to get better no-load characteristics and load characteristics; In the end, the axial thickness of stator core with long teeth and the pole arc coefficient is finalised.Lastly, the ralationship between force density and power factor is analyzed; The number of turns of winding, as the main factor to affect power factor, is studied primitively, number of turns of winding matching axial length is then chosen; The next step is to increase power factor and force density further by reducing air gap length; Upon this, this article optimizes the overlapping area of the stator teeth of adjacent stator pole. At the last, a motor with the efficiency more than 0.88, power factor up to 0.52, force density up to 2.17×105N/m3 is achieved.