Study on permanent magnet transverse flux machine

Abstract

This dissertation is concentrated mainly on the newest PMTF machine topology proposed and patented by Jacek F. Gieras in March 4, 2010. Such a topology (topology of 2010) is an object of this dissertation. A prototype that was built with 3D Finite Element Method (FEM) modeling of PMTF generator proves that the generator that was built on the basis of topology of 2010 has several significant disadvantages among which the greatest impact have high leakage flux losses. Applying FEM modeling, various steps to improve machine performance have been undertaken. Results obtained from modeling show, that keeping the same diameter and lengths of the machine as well as number of turns of the winding, output power of the machine can be two times higher and the negative flux linkage that is established by “inactive” PMs significantly reduced. This was achieved by introducing magnetic shunts to the stator structure. These shunts also reduce cogging torque. Modifications include changing machine stator structure, slot shape, and implementation of magnetic shunts which play a vital role in preventing flux leakage losses and reducing cogging torque. During modifications a big attention was paid to simplifying a manufacturing process. Modifications do not complicate machine design and count all aspects which may arise when manufacturing. Modified version of the PMTF machine was built by Polish manufacturer “Komel” for University of Nevada-Reno. This project was supported by National Science Foundation. The prototype results prove that the magnetic shunts block almost 70% of negative magnetic flux coming from inactive magnets. The induced voltage of the machine calculated using 3D FEM model is the same what was obtained during prototype laboratory test. However, the laboratory test also shows that if magnetic shunts are made of pure iron, generator has significant power losses. These power losses are caused by eddy currents induced on the magnetic shunts. To prevent eddy currents flowing on the magnetic shunts’ surface, instead of pure iron, laminated steel or magnetic powder has to be selected as a material for shunts. Combining the ideas of topologies [1-3] a new version of PMTF machine is introduced in this dissertation. Its electromechanical parameters are calculated. Three different designs of PMTF generator are compared in terms of output power to volume ratio.