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On Electrical Machine Topologies for Electric Vehicle Applications

Time: Fri 2022-11-18 10.00

Location: Kollegiesalen, Brinellvägen 8, Stockholm

Language: English

Doctoral student: Konstantina Bitsi , Elkraftteknik

Opponent: Professor Anouar Belahcen, Aalto University, Esbo, Finland

Supervisor: Professor Stefan Östlund, Elkraftteknik; Sjoerd Bosga, Elkraftteknik, ABB Corporate Research, Sweden

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QC 20221028


The deployment of electric vehicles is considered a viable solution towardsreducing the global greenhouse-gas emissions and fossil-fuel consumption. Inorder to produce highly efficient and economically feasible electrical drivesystems, the selection of suitable electric motor designs is a key step.The target of this work is to identify, analyze and compare suitable elec-trical machine topologies for automotive applications based on highly coupledand conflicting criteria. For this purpose, an evolutionary multi-objective op-timization is developed that can yield a set of Pareto-optimal solutions and,thus, offer different compromises among the considered design-objectives. Theefficacy of the algorithm is demonstrated, rendering it an important tool forthe subsequent analysis.In the first part of this thesis, the investigation of pole-phase changinginduction machines is presented. A special induction machine topology withwound, independently-controlled stator coils (WICSC) is introduced. Thestator-winding configuration in this machine permits the individual energiza-tion and current control of the toroidal coil in each stator slot, thus facilitatingthe real-time change of both phase and pole number. The 2D magnetic and3D thermal finite-element method (FEM) models of this machine are devel-oped, as well as an analytical transient model of the current dynamics. Adetailed investigation of the behavior of pole-phase changing induction ma-chines and the impact of their design on the selection of optimum pole-phaseoperations throughout the entire operating region is performed. Specifically,three WICSC machines that were originally designed with 2, 4 and 6 fixedmagnetic poles are evaluated as pole-phase changing machines with the aim ofdetermining the overall improvement in terms of torque per ampere capabilityand efficiency.The second part of this work is focused on the design and performance ofaxial-flux induction machines (AFIMs). An electromagnetic sizing algorithmfor the design of AFIMs is developed, which adopts a geometrical approachto the design problem, while minimizing the use of empirical factors. Theeffectiveness of this algorithm is experimentally validated, using a commercialdouble-stator AFIM utilized as an integrated starter generator in a hybridelectric vehicle application. Moreover, in order to assess the benefits of pole-changing in axial-flux structures, the optimization of an interior-permanentmagnet synchronous machine, a radial-flux WICSC machine and a double-rotor axial-flux WICSC machine is carried out for a heavy vehicle applicationand the comparison of their Pareto-optimal solutions is presented.