Electrical Machine Topologies Research Articles

Technical and Economic Analysis to Select Suitable Design Parameters of an E-Machine for Electric Commercial Vehicles

In the European Union (EU), road transport contributes a major proportion of the total greenhouse gas (GHG) emissions, of which a significant amount is caused by heavy-duty commercial vehicles (CV). The increasing number of emission regulations and penalties by the EU have forced commercial vehicle manufacturers to investigate powertrain technologies other than conventional internal combustion engines (ICE). Since vehicle economics plays an important role in purchase decisions and the powertrain of a battery electric vehicle (BEV) contributes to about 8–20% of the total vehicle cost and the electric machine (EM) alone contributes to 33–43% of the drivetrain cost, it is necessary to analyze suitable EM topologies for the powertrain. In this paper, the authors aim to analyze the technical and cost aspects of an EM for electric commercial vehicles (ECV). Based on prior research and literature on this subject, an appropriate methodology for selecting suitable geometrical parameters of an e-machine for the use case of a heavy-duty vehicle is developed using MATLAB and Simulink tools. Then, for the economic analysis of the e-machine, reference ones are used, and their design parameters and cost structures are utilized to develop a cost function. Different use cases are evaluated according to the vehicle’s application. The results for a use case are compared by varying the design parameters to find the most cost-effective EM. Later, an analysis is performed on other decisive factors for EM selection. This highlights the importance of collaborative consideration of technological as well as the economic aspects of EMs for different use cases in ECVs. The method developed in this work contributes to understand the economic aspect of EMs as well as considering their performance factors. State-of-the-art methods and research are used to develop a novel methodology that helps with the selection of the initial geometry of the electric motor during the design process, which can serve to aid future designers and converters of electric heavy-duty vehicles.

Determination of the Boundaries of the Non-Magnetic Phase of the Dual-Phase Magnetic Material of the Starter-Generator Rotor

Dual-phase magnetic material - a magnetic material in which, by processing, localized non-magnetic areas can be obtained to control the direction of the magnetic flux. Such properties can significantly improve the output characteristics of a number of topologies of electrical machines, as well as neutralize a number of the main disadvantages inherent in traditional designs of electrical machines. This paper presents a numerical study of the strength characteristics of the rotor of an electric starter-generator with permanent magnets with a dual-phase magnetic material. The optimal boundaries of racks for processing in the non-magnetic phase are determined.

Different Topologies of Electrical Machines, Storage Systems, and Power Electronic Converters and Their Control for Battery Electric Vehicles—A Technical Review

Electric vehicles (EVs) are emerging as an alternative transportation system owing to a reduction in depleting lubricates usage and greenhouse gas emissions. This paper presents a technical review of each and every sub-system and its feasible control of battery EV (BEV) propulsion units. The study includes the possible combination of electrical machines (EMs), storage system, and power electronic converters and their associated control strategies. The primary unit, i.e., EM, is the heart of the EV, which is used to drive the vehicle at the desired speed as well as to restore the regenerative braking (RB) energy that is generated to enhance the overall system reliability. To electrify the transportation sector, it is necessary to include new options of power electronic converter topologies and their associated control strategies for numerous reasons, which include extracting maximum power from sources in case the EV is powered from renewable energy resources, boosting the energy storage capability for longer electric range, managing power flow from the source to battery or battery to vehicle or vehicle to battery, and regulating the speed of the vehicle and braking control. Based on the survey, the suitable combination of sub-systems and their control for three and four-wheeler EVs are summarized in this paper.

Electrical machines in automotive: evaluation of current technologies and future requirements

This paper presents an evaluation of the current technologies and future requirements of electrical machine in automotive. First, a comparative of ten different electrical machines based on the market available electrical vehicles and hybrid electrical vehicles is made. The aim of the comparison is to evaluate the different electrical machine topologies, structure, operation conditions, and performance. The future design requirements of electrical machine in automotive are presented and several state-of-art electrical machine design techniques have been explored and studied by employing them in the compared ten machines. The conclusion of this work shows that permanent magnet topologies have the highest performance among the different electrical machine topologies and have the potential to meet the future requirements. In addition, aggressive cooling methods, i.e., spray, dripping, semi- or fully flooded, are needed to allow electrical machines to operate with the required power density target. Finally, the design to recycle concept shows the potential to be implemented in future electrical machines with little or no sacrifice of the performance.

Variational Autoencoder-Based Metamodeling for Multi-Objective Topology Optimization of Electrical Machines

Conventional magneto-static finite element (FE) analysis of electrical machine design is time-consuming and computationally expensive. Since each machine topology has a distinct set of parameters, design optimization is commonly performed independently. This article presents a novel method for predicting key performance indicators (KPIs) of differently parameterized electrical machine topologies at the same time by mapping a high-dimensional integrated design parameters in a lower-dimensional latent space using a variational autoencoder (VAE). After training, via a latent space, the decoder and multi-layer neural network will function as meta-models for sampling new designs and predicting associated KPIs, respectively. This enables parameter-based concurrent multi-topology optimization.

Dynamic Characteristics and Demonstration of an Integrated Linear Engine Generator with Alternative Electrical Machines

A linear engine generator with a compact double-acting free piston mechanism allows for full integration of the combustion engine and generator, which provides an alternative chemical-to-electrical energy converter with a higher volumetric power density for the electrification of automobiles, trains, and ships. This paper aims to analyse the performance of the integrated engine with alternative permanent magnet linear tubular electrical machine topologies using a coupled dynamic model in Siemens Simcenter software. Two types of alternative generator configurations are compared, namely long translator-short stator and short translator-long stator linear machines. The dynamic models of the linear engine and linear generator, validated with lab-scale prototypes, are applied to investigate the influence of alternative topologies of the generator on system performance. The coupled model will facilitate the early design phase and reveal the optimal match of the key parameters of the engine and generator. Then, experimental tests on an integrated compressor cylinder-generator prototype were successfully performed, and it is shown that this concept is feasible and electrical power and compressed working fluid, such as air, can be generated by this prototype.

Obtaining a dual-phase magnetic material based on electrical silicon steel sheet

Dual-phase magnetic materials are materials that have different magnetic permeability in selected areas. This feature of dual-phase magnetic materials opens up great prospects for new design solutions for some topologies of electrical machines. This article presents the results of a study on obtaining a dual-phase magnetic material from sheets of electrical silicon steel with a Si content of 2.4–3.8% during ion-plasma nitriding in a glow discharge. Based on the optimal parameters of the vacuum environment, samples of silicon steel sheets were processed with different holding times. Then, the structure of each of the samples was studied using an X-ray diffractometer with the determination of the composition of the surface layer of the treated samples and the identification of the non-magnetic phase. As a result of the study, the possibility of obtaining a non-magnetic austenite phase during ion-plasma nitriding was shown, however, the formation of a significant amount of the nitride phase was noted. An experiment on transformers shows a decrease in magnetic permeability and magnetization for a dual-phase magnetic material. Strength tests show satisfactory characteristics for the non-magnetic phase of the obtained dual-phase magnetic material, as well as a strong decrease in strength characteristics for the magnetic phase of the dual-phase magnetic material.

A Tutorial on General Air-Gap Field Modulation Theory for Electrical Machines

This tutorial paper presents the mathematics behind the widely observed air-gap field modulation phenomena in electrical machines and derives the duality between electrical machines and switching converters. A bibliometric analysis of the existing research on various machine types is presented to show the historical development of electrical machines from the perspective of the number of publications, showing the necessity and urgency of unifying the analysis of operating principles/torque production mechanisms before the development of the general air-gap field modulation theory in 2017. The theoretical framework and its applications are reviewed. Detailed examples of how to use the developed theory to analyze the operating principle/torque production, conduct the quantitative analysis of parameters and basic performance, and make innovations from topologies of typical electrical machines are also included for verification as well as self-study.

Design And Optimization Of A Brushless Motor Applied To A Formula SAE Vehicle

The purpose of this paper is to describe the methodology adopted to design an electric motor applied to the traction of a single-seat high-performance electric vehicle. A comparative selection of topologies of electrical machines is made and then, an analytical model of the chosen layout is described. An evolutionary algorithm is used in order to find an optimized solution according to some selected performance criteria. Afterwards, the analysis of the selected design is made in a finite element simulation software. Finally, a comparison between the analytical and the finite element models results is performed.

Additive Manufacturing of Shaped Profile Windings for Minimal AC Loss in Electrical Machines

Metal additive manufacturing enables production of copper and aluminium parts exhibiting unmatched geometric freedom, giving rise to new possibilities in the winding design of electrical machines and wound passive components. Early adopters of additive manufacturing are primarily concerned with improving power-density or efficiency by increasing slot fill-factor, optimizing end-winding topology or incorporating cooling channels into the conductors. In this article, a method of minimizing the elevated ac loss present in open slot electrical machine topologies is presented, in which individual conductor profiles are shaped according to their magnetic environment. Such shaped profile windings are shown to exhibit operating mode dependent loss behavior giving them potential for efficiency improvement in applications with a dominant operating mode such as electric vehicle traction, aerospace propulsion fans, and generators. For the first time, the conductor shaping method and associated benefits are demonstrated by the retrospective design, additive manufacture, and experimental test of a three-phase set of shaped profile windings for a concentrated wound, open slot, permanent magnet electrical machine.

A 300 000-r/min Magnetically Levitated Reaction Wheel Demonstrator

Magnetic bearings can be used in reaction wheel systems to avoid several drawbacks of ball bearings, such as limited lifetime due to mechanical friction and lubricant monitoring/sealing requirements. Therefore, this letter discusses an electrical machine topology with integrated reaction wheel and magnetic bearings. The slotless/ironless structure, together with a new electromagnetic arrangement resulting in a shorter rotor than in earlier works, enables efficient operation at very high speeds, which in turn enables the miniaturization of the system. Measurements taken on a demonstrator prototype at 300 000 r/min show a significant increase of the feasible operational speed range compared to the state-of-the-art reaction wheels for small satellites, which typically run below 10 000 r/min.

Study of a Novel High-Speed Compensated Pulsed Alternator With Multistage Stator Cores

The compensated pulsed alternators (CPAs) have good applications in high-energy lasers, electromagnetic rail guns, and other electromagnetic launch devices. Among various electrical machine topologies, homopolar inductor alternators (HIAs) have attracted interest as CPAs due to their merits of simple and reliable structure, brushless excitation, and high-speed operation. However, the length of the conventional HIA is difficult to expand because it is limited by the rotor diameter, and the rotor diameter is restricted by the maximum speed of rotor tip, which results in low-energy storage capacity of a single machine. Besides, HIA suffers from the relatively low-power density due to its unipolar air-gap flux density (UAFD). To solve these problems, two novel HIAs with multistage stator cores (HIA-MSCs) are proposed in this paper. One is HIA with UAFD (HIA-UAFD) and the other is HIA with unipolar and bipolar air-gap flux density (HIA-UBAFD). First, the structure and operation principle of HIA-MSCs are illustrated. Then, the key parameters of HIA-MSCs are derived, and the corresponding models are built. Finally, the electromagnetic performances of HIA-MSCs are investigated by 3-D finite-element analysis method. Compared with HIA-UAFD, HIA-UBAFD has relatively higher discharge current and output power, which indicates that HIA-UBAFD is a better candidate for the pulsed alternator.

Optimization of Electric Powertrains Based on Scalable Cost and Performance Models

This work presents a methodology for modeling, designing, and scaling the electromagnetic, mechanical, and thermal characteristics of the main components in an electric powertrain (excluding the battery), i.e., a power electronics converter, an electrical machine, and mechanical transmission. Additionally, a framework for estimating the cost of these components is described. This framework takes into consideration not only the material cost, but also all major manufacturing steps required for the production of a component and their dependence on expected production volumes. Moreover, a procedure to optimize the design of an electric powertrain, taking advantage of the aforementioned models, is proposed. Finally, the powertrain for a passenger electric vehicle is optimized using the proposed methodology, and the results are compared in terms of the electrical machine topology, powertrain concepts, cost, weight, gear ratio(s) in the transmission, and overloading capabilities.

Optimization of Electric Machine Designs - Part II

This Special Section on Optimization of Electrical Machine Designs summarizes the state-of-the-art on the latest researches carried out on the topic, both in the academic and industrial environments. Basically, all the electrical machine topologies and optimization techniques have been discussed in this Section, suggesting to the readers interesting solutions of several optimization problems related with modern applications. The second part of the special section (the first one has been published in the December 2017 issue of the IEEE Transactions on Industrial Electronics) includes 20 papers from a total of 44 accepted contributions. The studies included in the Part II are categorized in a table and are outlined to some extent in order to help the readers to quickly compare the main peculiarities of the mathematical approaches and the practical implementations. The Part II paper categorization of this Special Section presents a second set of four papers focused on the permanent magnet synchronous machines

Comparison of High-Speed Electrical Motors for a Turbo Circulator Application

This paper presents an analysis of three different electrical machine topologies for a turbo circulator application. The electrical machines are designed to operate with 6 kW output power at 120 000 r/min. This paper demonstrates the design aspects of one solid rotor squirrel cage induction motor and two permanent magnet synchronous machines. The machines are compared using electromagnetic, thermal, and mechanical analyses. The benefits and disadvantages of each topology under study are discussed. For other high-speed applications presented, a comparative approach helps in selecting the suitable electrical machine topology by analyzing the performance criteria discussed. The prototype construction of one of the topologies is analyzed.

Topology Evaluation of a Slotless High-Speed Electrical Machine with Stator Core Made of an Amorphous Alloy for the Aerospace Industry

The paper presents the experimental research of different slotless high-speed electrical machine topologies for integration into the auxiliary power unit gearless. It was shown that the 6-poles and 8-poles with the concentrated windings and the wound stator core are the most effective for aerospace industry. Based on the experimental and computer research of different slotless high-speed electrical machine topologies. It was found that for use in the gearless auxiliary power unit of modern and perspective aircrafts, the use of the 6-poles and 8-poles slotless high-speed electrical machines with concentrated windings and wound stator core is the most effective. This topology allows providing the sufficient rigidity of the slotless high-speed electrical machine stator core, the minimum length of the frontal part and the minimum weight and size parameters of the slotless high-speed electrical machine at the maximum efficiency. In addition, in this case, the slotless high-speed electrical machine windings have a high inductance, which leads to limit the magnitude of short circuit currents.

Concept of Integration of Axial-Flow Compression Into Electric Machine Design

The purpose of this paper is to propose a novel concept of a high-speed electric machine system with integrated airfoil-shaped rotor designed to perform axial-flow compression for vehicle applications. The proposed high-speed machine is both a motor for electromagnetic (EM) energy conversion and an axial flow compressor for thermodynamic energy conversion. Conventional designs usually have a separate motor and compressor that are connected through a common shaft with or without a gearbox. The proposed design simplifies the high-speed machine and compressor system by eliminating the components that connect the motor and the compressor. The integrated motor-compressor design can achieve a more compact system. The flux-switching permanent magnet (FSPM) machine is chosen out of several possible electric machine topologies with salient rotor pole features for the integrated motor design. The feasibility of this integrated motor-compressor design is discussed from both the EM and thermodynamic perspectives in this paper. The selection of slot/pole combination and EM sizing equations for the integrated FSPM motor-compressor are discussed. Mean-line design equations for the axial flow compressor are studied for the proposed integrated motor-compressor. The EM torque production capability of the proposed integrated motor-compressor is verified for one possible design in this paper by finite element analysis (FEA). The effects of two different attack angles of the rotor blades are studied compared to the conventional FSPM machine. The FEA results show that the proposed integrated motor-compressor achieves the expected output performances.

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.

Multiphase starter generator for 48V mini-hybrid powertrain: design and testing

This paper focuses on the design and experimental test results of a belt-driven starter generator for 48-V mini-hybrid powertrains. The functionalities required of the system are engine startup, launch assistant torque, regenerative braking, battery charging, and early fuel cutoff. The cost-effective electrical machine must provide high starting torque and wide constant power speed range, both in motor and generator modes. The authors outline the motivations of the electrical machine topology selection in relation to the specifications and constraints. In particular, a double three-phase induction machine has been selected as a suitable candidate. The aim of this paper is to summarize the design challenges of such kind of electrical machines, mainly subordinated to electromechanical and thermal issues imposed by the considered hybridization solution. Details of the machine design are presented, including a study on multilayer bar stator windings and on rotor slot design. Finally, predicted and measured performances of the prototype are reported and discussed for validation purposes.

Electrical Machine Topologies: Hottest Topics in the Electrical Machine Research Community

Electrical machines are generating and using most of the electrical energy converted worldwide from fossil fuels or renewable sources. An optimized electrical machine means not only less input energy used but also higher electromechanical energy available as output. This is translated into getting more with less and having an impact on the total amount of greenhouse gases released into the atmosphere, thus mitigating global warming. Benefiting from the latest developments in the electrical machine field are various industries such as electric propulsion [new electric vehicles (EVs) and plug-in hybrid EVs (HEVs)], renewable energy harvesting, consumer applications, and military and aerospace products. This article brings together the contributions from several authors working in academia and industrial research and development centers and comprises a collection of short analyses dedicated to the hottest topics in the electrical machine research community. The article focuses on special and difficult problems to be solved in the design process of the most important electrical machine topologies. The topics discussed cover new machine topologies such as fractional slot winding motors and synchronous reluctance motors; electromagnetic, mechanical, and thermal problems in permanent magnet (PM) machines design; operation of high-speed machines and high-power turbo generators; noise and vibration reduction in switched reluctance motors (SRMs) for automotive applications; high-efficiency induction machines (IMs) configurations compatible with the new international standard and a comprehensive analysis of universal motors (UMs).