Advanced Electrical Machines and Machine-Based Systems for Electric and Hybrid Vehicles

The paper presents a number of advanced solutions on electric machines and machine-based systems for the powertrain of electric vehicles (EVs). Two types of systems are considered, namely the drive systems designated to the EV propulsion and the power split devices utilized in the popular series-parallel hybrid electric vehicle architecture. After reviewing the main requirements for the electric drive systems, the paper illustrates advanced electric machine topologies, including a stator permanent magnet (stator-PM) motor, a hybrid-excitation motor, a flux memory motor and a redundant motor structure. Then, it illustrates advanced electric drive systems, such as the magnetic-geared in-wheel drive and the integrated starter generator (ISG). Finally, three machine-based implementations of the power split devices are expounded, built up around the dual-rotor PM machine, the dual-stator PM brushless machine and the magnetic-geared dual-rotor machine. As a conclusion, the development trends in the field of electric machines and machine-based systems for EVs are summarized

Emerging Multiport Electrical Machines and Systems: Past Developments, Current Challenges, and Future Prospects

Distinct from the conventional machines with only one electrical and one mechanical port, electrical machines featuring multiple electrical/mechanical ports (the so-called multiport electrical machines) provide a compact, flexible, and highly efficient manner to convert and/or transfer energies among different ports. This paper attempts to make a comprehensive overview of the existing multiport topologies, from fundamental characteristics to advanced modeling, analysis, and control, with particular emphasis on the extensively investigated brushless doubly fed machines for highly reliable wind turbines and power split devices for hybrid electric vehicles. A qualitative review approach is mainly adopted, but strong efforts are also made to quantitatively highlight the electromagnetic and control performance. Research challenges are identified, and future trends are discussed

Overview of Stator Slot-opening Permanent Magnet Machines

In the past few decades, the stator permanent magnet (PM) machines have attracted much research attention because of their reliable rotor structure, high power density, wide speed range, and strong fault-tolerant ability. Among the recently proposed stator PM machine topologies, the stator slot-opening PM (SS-PM) machines are becoming increasingly popular because of their higher stator space utilization and robust rotor structure. According to the SS-PM magnetization direction, the SS-PM machines can be classified into three categories, namely, the tangentially magnetized stator slot-opening PM (TMSS-PM) machines, the radially magnetized stator slot-opening PM (RMSS-PM) machines, and the compound magnetized stator slot-opening PM (CMSS-PM) machines. The associated working principle and electromagnetic performance of different SS-PM machines can be diverse. Therefore, this paper gives an overview of SS-PM machines in terms of machine design, working principle, and machine performance. A qualitative performance evaluation and comparative study of SS-PM machines are presented, and the future challenges and potential opportunities in the SS-PM machine design are discussed

Switched Flux Permanent Magnet Brushless Machines for Electric Vehicles

This thesis investigates different topologies of switched flux permanent magnet (SFPM) machines and variable flux (VF) methods for high speed applications. Although several novel topologies of SFPM machines have been proposed and investigated recently, their torque-speed capability has not been studied systematically. Therefore, the torque-speed capability as well as the open circuit and electromagnetic performance of conventional SFPM machines with three different stator/rotor pole combinations, i.e. 12/10, 12/13 and 12/14, and three novel SFPM machine topologies, i.e. multi-tooth, E-core and C-core are analysed and investigated by the finite element (FE) method and experiments. Moreover, in order to improve the flux-weakening capability of these machines a variable flux method using flux adjusters (FAs) is employed and the corresponding electromagnetic performance of the machines are investigated, analysed and compared. Both FE and measured results show when the FAs are used the torque-speed capability of the three conventional machines can be improved significantly, while no improvement is shown in the three novel topologies primarily due to the large winding inductances. The technique of using flux adjusters has been improved by reducing the number of FAs. Thus, a new mechanical variable-flux machine topology, which uses only half of FAs outside the stator at alternative stator poles, is proposed, developed and analysed. Open circuit results, electromagnetic performance and torque- and power-speed curves of the 12/10, 12/13 and 12/14 stator/rotor pole SFPM machines with alternative FAs are predicted and compared by 2D and 3D-FE, and experimentally validated. Furthermore, a novel SFPM machine topology with radial and circumferential PMs is proposed, investigated and optimized. This topology reduces the stator flux leakage and offers high magnetic utilization. Moreover, this topology can also be developed as a mechanical variable flux machine. Finally, three SFPM machines with variable flux techniques, i.e. mechanically movable flux adjusters (MMFA), mechanically rotatable permanent magnet set (MRMS) and hybrid excitation with backside DC coils (HEBC) are analysed. Their open circuit results and electromagnetic performance with emphasis on torque-speed characteristic are investigated and compared. Additionally, the required power to switch between flux weakening and strengthening states, flux weakening capability and permanent magnet demagnetization withstand capability are predicted, analysed and compared. The influence of end-effect on the torque-speed capability in the conventional, multi-tooth, E-core and C-core SFPM machines is investigated. Measurements and 3D-FE are performed to obtain the torque-speed curve in order to validate the findings of the research. The 3D-FE predicted results match well with the measured results, while the 2D-FE predicted results are lower due to the high end-effect in the SFPM machines

Design of segmental rotor and non-overlap windings in single-phase fefsm for low torque high speed applications

In this research, a new structure of single-phase field excitation flux switching motor (FEFSM) using segmental rotor structure and non-overlap windings arrangement is proposed in order to overcome the drawbacks of low torque and small power performances due to their longer flux path in the single-phase FEFSM using salient rotor structure and overlap windings arrangement. The objectives of this study are to design, analyse and examine performance of the proposed motor, to optimize the proposed motor for optimal performances, and to develop the proposed motor prototype for experimental performance validation. The design and analyses thru 2Dfinite element analysis (FEA) is conducted using JMAG Designer version 15, while deterministic optimization method is applied in design optimization process. To validate the 2D-FEA results, the motor prototype is developed and tested experimentally. Based on various rotor poles analysis, a combination of 12 pole 6 pole (12S-6P) has been selected as the best design due to their highest torque and power capability of 0.91 Nm and 277.4 W, respectively. Besides, the unbalance armature magnetic flux of the proposed FEFSM using segmental rotor has been resolved by using segmental rotor span refinement. The balanced armature magnetic flux amplitude ratio obtained is 1.002, almost 41.2% reduction from the initial design. In addition, the optimized motor has increased maximum torque and power by 80.25% to 1.65 Nm, and 43.6% to 398.6W, respectively. Moreover, copper loss of the optimized design has decreased by 9.7%%, hence increasing the motor efficiency of 25.3%. Finally, the measured results obtained from the prototype machine has reasonable agreement with FEA results, proving their prospect to be applied for industrial and home appliances

Flux switching machine design for high-speed geared drives

Electrical machines capable of high-speed operation are key technology used in many modern applications, such as gas turbine electrical systems, high-speed fly-wheels, turbochargers, and computer numerical control (CNC) machines. The use of geared high-speed machines to replace low-speed high torque drives has not been adequately researched to-date. The rationale of this thesis is to investigate a candidate high speed machine, namely flux switching machines to be used together with new types of core material with mechanical gearing to deliver high-torque and low speeds. Modern developments in advanced material technology have produced new magnetic materials capable of dealing with high resulting in very low losses in high speed machines. However, such metals typically have low mechanical strength, and they are found to be brittle. In order to manufacture electromechanical device with such new materials, it has to be reinforced with a mechanically strong structure. The use of multiple types of magnetic materials referred as a MMLC has been proposed in this thesis for high-speed machine design. In this research, a generic method using magnetic equivalent circuit to model flux switching machines (FSMs) is investigated. Moreover modeling, based on machine dimensions for multiphase FSMs having any pole and slot number has been introduced. The air-gap permeance modeling to simplify the magnetic circuit calculation of FSMs was also investigated in this thesis. It is shown that the permeability of magnetic material can be adjusted with the use of MMLC material. Using this feature, the FSM mathematical model is used to show the impact on electromagnetic performance using MMLCs and is shown to be beneficial. In order the evaluate the weight benefits of using geared high speed FSMs, the planetary gear systems are studies and their design constraints have been identified. An abstract form of weight estimation for given torque and speed requirements has been developed and validated using commercially available planetary gear specifications. FSMs together with gear boxes have been considered and it is shown that significant weight savings can be achieved at higher diameter and at high speeds

Semi-Analytical Approach Towards Design and Optimization of Induction Machines for Electric Vehicles

Electric machine design is a comprehensive task depending on the several factors, such as material resource limitations and economic factors. Therefore, an induction machine is a promising candidate because of the absence of magnetic material in the rotor. However, the conventional design approach can neither reflect the advances of the induction machine(IM) design nor exploit the trade-offs between design factors and the multi-physics nature of the electrical machine. Therefore, proposing fast and accurate novel methods to design, develop and analyze IMs using electromagnetic field oriented approaches is competitive to the old-fashion numerical methods. To achieve improved IM design from a baseline design to an optimal design, this dissertation: (1) Investigates the challenges of the high speed IM design specified for the electric vehicle application at the rated operating condition considering electromagnetic boundaries for the reasonable saturation level within a compact volume; (2) Proposes a new design approach of IM using modified equivalent circuit parameters to reduce spatial harmonics because of slotting effect and skewing effect; and also presents the importance of the 3-D analysis over 2-D analysis while developing the IM; (3) Proposes a novel electromagnetic field oriented mathematical model considering the slotting effect and axial flux variation because of skewing rotor bars to evaluate the IM performance with a lower and precise computational effort; (4) developed baseline IM is optimized with genetic algorithm incorporated in proposed subdomain model to improve the torque-speed profile. In order to further simplify the optimization procedure, a parametric and sensitivity based design approach is implemented to reduce the design variables. To evaluate the proposed optimal IM with extended constant power region and high torque density within a compact volume using novel 3-D subdomain model, the machine has been prototyped and tested from low to high speed under no-load and loaded condition. Electrical circuit parameter variation is demonstrated and compared to the one simulated in the FEA environment. This innovation can be applied to a family of electric machines with various topologies

Flux switching machines using segmental rotors

Flux switching machines (FSM) employing a segmental rotor have field and armature systems on the stator and a presentation of an unexcited rotor with isolated segments. The single-tooth winding arrangement on the stator provides a potential for material and energy savings. The principle for producing bipolar flux in the armature stator teeth relies on the natural switching of the armature tooth flux, accomplished by the moving segments of the rotor. Three phase configurations have been studied, from conception and design to construction and testing, with field excitation provided by either a field winding or permanent magnets (PM). Flux switching machines have shown characteristics that are peculiar when employing a segmental rotor, significantly affecting the symmetry of the induced armature EMF waveform and parity of magnitudes of the positive and negative torques. For three phase operation, six topologies are feasible when employing a 12-tooth stator and two other topologies may be produced on a 24-tooth stator. An optimum topology on the 12/8-configuration and another proof-of-principle topology on the 12/5-configuration, using field-windings and permanent-magnets, have been designed and constructed, while applying modern practices and considerations for manufacture. The characteristics of FSMs employing a segmental rotor, initially predicted by finiteelement (FE) modelling, have been verified by measurements. The FSM employing a field-winding is found to have a specific torque output which is similar to the conventional switched reluctance motor and still substantially higher than that of the synchronous reluctance motor. Although the PM adaptation of the FSM produces specific torque output which is nearly twice that of the wound-field FSM and about 64% that of an equivalent permanent-magnet synchronous motor (PMSM) with surface or insert magnets, accounting for the usage of the magnets reflects its specific torque output to be about 1.48 times higher than the PMSM. Although the FSM is operated as an AC machine with sinusoidal three-phase currents, its dq-equivalent representation shows significant differences from that of the conventional AC machine. In the prediction of the performance, it is found, in both the wound-field and PM configurations, that the dq model is more dependable if the coupling dq inductance is taken into account.EThOS - Electronic Theses Online ServiceCommonwealth Scholarship Commission of UKGBUnited Kingdo

Advances in Rotating Electric Machines

It is difficult to imagine a modern society without rotating electric machines. Their use has been increasing not only in the traditional fields of application but also in more contemporary fields, including renewable energy conversion systems, electric aircraft, aerospace, electric vehicles, unmanned propulsion systems, robotics, etc. This has contributed to advances in the materials, design methodologies, modeling tools, and manufacturing processes of current electric machines, which are characterized by high compactness, low weight, high power density, high torque density, and high reliability. On the other hand, the growing use of electric machines and drives in more critical applications has pushed forward the research in the area of condition monitoring and fault tolerance, leading to the development of more reliable diagnostic techniques and more fault-tolerant machines. This book presents and disseminates the most recent advances related to the theory, design, modeling, application, control, and condition monitoring of all types of rotating electric machines