Tooth-coil wound multiphase synchronous machines

Nowadays we are witnessing a strong growth in the full electric vehicle market. In the field of traction the requirements are low weight, small dimensions and low cost, without renouncing reliability and good performances. The high power density requirement is pushing the research towards integrated drive solutions. A particular drive that allows to obtain more insightful integrated solutions is the multi-phase one. In fact, in multi-phase structures it is possible to realize a converter as a combination of standard modules with an equal subdivision of the current. The resulting power electronics modules meet the needs of an integrated solution: smaller and widely distributed. Although road electric vehicles primarily adopt 3-phase drives, the multi-phase version could represent a good alternative not only for its integration capability but also for other features like reduced weight and volume, high efficiency, low vibrations and noise, robustness and, overall, fault tolerance. The aim of this thesis is to investigate a particular category of multiphase machines, characterized by a very simple structure that allows to match manufacturing and performance standards. In Chapter 1, the subcategory of multiphase machine object of the investigation is identified. Considering a simple stator structure, as the tooth-coil wound, a general algorithm to identify the right stator-rotor coupling in multiphase machine is presented. In Chapter 2, an analytical and generalized formulation of the harmonic fields at the air gap for the multi-n-phase solutions chosen is reported allowing to understand and quantify the harmonic compensation in the MMF. Starting from the Lorenz Force Law an analytical formulation of the torque and torque ripple is then proposed. The model proposed has been then verified by Finite Element Analysis (FEA). In Chapter 3, the main issues tackled in the design of a nine phase machine are reported. Between the possible solutions a 9 slot 10 poles PM-inset machine has been chosen. The chapter reports the evaluation of the performance conducted by the time stepping FEA. The chapter reports the experimental results that were conducted on a prototype. A description of the control infrastructure is reported. In Chapter 4, a simple modulation strategy that allows to reduce the DC-link stress for a triple-3-phase drive is presented. The analysis of the benefits introduced by the PWM phase shifting are evaluated by steady state simulations ,using the software Pspice, in all the possible operating conditions. A worst case approach has been chosen in order to find the best angle of shifting between carriers to reduce the DC-link rms current in multi-3-phase drives. The results of the experimental validation are reported. The same analysis has been extended to sectored multiphase. In Chapter 5, a mathematical model is proposed in order to evaluate the torque and the torque ripple in fractional slot tooth-coil wound (TCW) Synchronous Reluctance (SyR) machines. Considering a generic harmonic field and an ideal SyR rotor, the rotor magnetic potential is modelled and the torque equations are calculated starting from the Lorenz Force Law. Time stepping FEA results are reported in order to verify the formulations. Appendix A reports the mathematical demonstration that defines the rotor reaction for an ideal SyR rotor together with the methodologies used to design the SyR constant permeance rotor. Appendix B reports the manufacturing process of the machine. Appendix C reports the COOL-TIE concept: a cooling devices for the electrical machine compatible with the power electronic integration