Machine For Electric Vehicles Research Articles

Multi-mode operations of double-stator switched reluctance machine for electric vehicle

PurposeThe purpose of this paper is to introduce a double-stator switched reluctance machine (DS-SRM) for electric vehicles (EVs) and to propose multi-mode operations for this machine.Design/methodology/approachAnalysis of flux linkage distributions and torque characteristics using finite element method (FEM). Building a dynamic simulation model based on electromagnetic characteristics, mathematical equations and mechanical motion equations of the DS-SRM drive system. The paper proposes multi-mode operations (inner-stator excitation mode, outer-stator excitation mode and double-stator excitation mode) based on motor working regions. It also conducts simulation and experimental results to verify the effectiveness of the proposed multi-mode operations strategies and control schemes.FindingsThere is almost no electromagnetic coupling between the inner and outer stators due to the specially designed rotor structure and optimized windings polarity configuration. Analysis of flux linkage distributions and torque characteristics verified the independence of inner and outer stators. Proposal of multi-mode operations and corresponding control rules achieved the smooth switching between different modes.Originality/valueThe paper introduced the DS-SRM for EVs and proposed multi-mode operations, along with control rules, to optimize its performance. The specially designed rotor structure, optimized winding polarity configuration, and the proposed multi-mode operations contribute to the originality of the research.

Accurate Time-Efficient Thermal Modeling and Discretization Methodology Applied to Electric Machines

The increasing power density of electric machines for electric vehicles necessitates accurate thermal analysis in design and real-time condition monitoring through simulations with computation times not exceeding one minute. Existing thermal models are either accurate and complex while requiring large computation times or they are fast but lack accuracy. To address these challenges, a novel hybrid modeling methodology is proposed, combining 3D lumped parameter thermal networks with thermal resistances extracted from 2D finite element models (FEM) to reduce computation demands while preserving accuracy. Further, a methodology is introduced to define the thermal network discretization for a desired threshold accuracy while minimizing computation time. Analysis of this discretization methodology demonstrates that the desired accuracy can be reliably achieved with limited computational effort. Verification of the modeling methodology against 3D FEM in OpenFOAM shows key component temperature deviations of less than 0.67 °C in steady-state simulations and 0.75 °C in transient simulations, comparable to the 3D FEM uncertainty of 0.39 °C. The computation times for steady-state and transient simulations are 18.3 s and 43.5 s respectively compared to 44 h and 175 h for 3D FEM. This highlights the time efficiency of the proposed methodology while maintaining accuracy for key component temperatures.

The Current Region Control Strategy With Wide Speed Range of Radial-Axial Consequent Pole Hybrid Excitation Machine for Electric Vehicles

The Current Region Control Strategy With Wide Speed Range of Radial-Axial Consequent Pole Hybrid Excitation Machine for Electric Vehicles

Production cost modeling for permanent magnet synchronous machines for electric vehicles

A cost model for the estimation of production costs of permanent magnet synchronous machines (PMSM) is presented, which allows to alter design choices such as wire technology, winding layout, cooling system, materials and more. With the goal to make results reproducible by others, the methods are explained in detail and used data and assumptions are given. The developed model helps to understand the interaction between the design of PMSM, manufacturing methods and the resulting costs. With it, different PMSM technologies and materials can be evaluated regarding its influence on the production costs, which is a perquisite to find the best compromise between performance and costs. Production volume is shown to be the most decisive factor for the resulting production costs. Between minimum and maximum assumed volumes, an average cost per unit reduction of 67% could be observed. Furthermore, the results imply that the winding production is responsible for the greatest part of the overall costs, followed by the rotor assembly (including rare earth magnets). When using the model to compare different wire types, it can be stated that up to a production volume of roughly 150,000 units/year, hairpin wires are more expensive to produce. Above this volume, hairpin windings will get cheaper than round wire windings due to its higher grade of automation of the production process. Through the conducted investigations and the presented results, it is demonstrated that the cost model can serve to evaluate technologies with regards to costs in the early development stage. This way a more holistic assessment of technologies for PMSM is possible, helping to find the ideal compromises between costs and performance and to increase the attractiveness of sustainable mobility.

Magnetic Circuit Feature Investigation of a Radial–Axial Brushless Hybrid Excitation Machine for Electric Vehicles

The magnetic circuit feature of a radial–axial brushless hybrid excitation machine (RA-BHEM) is studied in this article. An axial stator is placed on one side of the rotor, which is wound with ac excitation winding to adjust the air-gap flux flexibly to make it have good flux regulation capability. The flux distribution of the RA-BHEM is a radial–axial 3-D mixed magnetic circuit, which is difficult to be analyzed by the 2-D finite-element analysis (FEA). Therefore, a radial–axial equivalent magnetic circuit (RAEMC) model is established to obtain the air-gap flux density with different excitation magnetomotive forces (MMFs), which simplifies the design process and reduces the amount of calculation. The flux density distribution in different MMFs is analyzed by 3-D finite FEA and the results are consistent with the RAEMC model results. The torque characteristics in the low-speed region and the flux-weakening capability in the high-speed region are analyzed to verify the possibility of the proposed machine in the field of electric vehicles (EVs). Finally, a 2-kW prototype is manufactured to verify the correctness of the above analysis.

Design and optimisation of energy‐efficient PM‐assisted synchronous reluctance machines for electric vehicles

AbstractThe design and optimisation of a permanent magnet‐assisted synchronous reluctance (PMaSynR) traction machine is described to improve its energy efficiency over a selection of driving cycles, when installed on a four‐wheel‐drive electrically powered vehicle for urban use, with two on‐board powertrains. The driving cycle‐based optimisation is defined with the objective of minimising motor energy loss under strict size constraints, while maintaining the peak torque and restricting the torque ripple. The key design parameters that exert the most significant influence on the selected performance indicators are identified through a parametric sensitivity analysis. The optimisation brings a motor design that is characterised by an energy loss reduction of 8.2% over the WLTP Class 2 driving cycle and 11.7% over the NEDC and Artemis Urban driving cycles, at the price of a 4.7% peak torque reduction with respect to the baseline machine. Additional analysis, implemented outside the optimisation framework, revealed that different coil turn adjustments would reduce the energy loss along the considered driving cycles. However, under realistic size constraints, the optimal design solutions are the same.

Interturn Short-Circuit Fault Diagnosis of Interior Permanent Magnet Synchronous Motor for Electric Vehicle Based on Search Coil

This article proposes an interturn short-circuit fault diagnosis method for permanent magnet synchronous machines for electric vehicles based on search coils (SC) with a unique structure. In this proposed structure, the SCs are uniformly wound in the main flux direction of each phase, and the number of SCs is twice the number of phases, resulting in significant cost savings. Based on this structure, a novel fault feature based on the negative-sequence components of the second carrier frequency sideband harmonics in the voltage signal of the SC is proposed. As a result, this fault characteristic frequency component is not only more obvious than the fundamental component used in the traditional SCs method but also can be transformed to a dc indicator by two coordinate transformations, which is conducive to online implementation in both stationary and nonstationary conditions. Finally, experiments are presented to verify the proposed diagnosis strategy.

Multi-Objective Optimization Framework of a Radial-Axial Hybrid Excitation Machine for Electric Vehicles

This paper proposes a multi-objective optimization framework for a radial-axial hybrid excitation machine (RAHEM) to provide higher average torque, better flux regulation ability and smaller torque ripple, which are applied to electric vehicles (EVs). The design variables related to multiple-objective are analyzed by sensitivity stratification. Non-dominated sorting genetic algorithm II (NSGA-II) based on response surface model (RSM) is adopted for the high sensitivity layer variable. The advantages are selected with the pareto optimal solutions (POS), while the low sensitivity layer variables are optimized by sensitivity ranking for single parameter scanning. The optimization function compares the two sensitive layers results to obtain the optimal design. Three-dimensional (3-D) finite element analysis (FEA) is used to compare the electromagnetic performance of initial and optimal designs. Finally, a prototype is manufactured to verify the effectiveness of the proposed framework.

Optimal Design of High-Speed Electric Machines for Electric Vehicles: A Case Study of 100 kW V-Shaped Interior PMSM

The need of compact machines increased in recent years due to increases in raw materials’ price. Hence, many studies are currently being conducted on high-speed challenges to propose an optimal design methodology. AC losses in windings are often not included in the optimization process and are treated in post-processing by choosing a suitable conductor’s diameter to mitigate skin and proximity effects. This paper presents an optimization and design methodology for high-speed electric machines considering these losses, using models with an interesting trade-off between computation time and accuracy, which is helpful for large-scale optimization, in which more than 9,600,000 machines are evaluated. Optimizations are conducted on 100 kW high-speed one-layer V-shaped interior permanent magnet synchronous machines, widely used in vehicles thanks to their high power density, based on the specifications of the Peugeot e208, for different values of pole pairs and maximum speed. The influence of lamination thickness, fill factor, and maximum current density on the optimal design is also investigated. This paper concludes the utility of increasing speed to achieve high power density and proposes best alternatives regarding automotive constraints. Results show that the number of pole pairs is not always a key parameter in obtaining the lowest volume, especially at high speed.

Multi-objective optimisation design for brushless electrically excitated synchronous machines in electric vehicles

Multi-objective optimisation design for brushless electrically excitated synchronous machines in electric vehicles

Multi-objective optimisation design for brushless electrically excitated synchronous machines in electric vehicles

Multi-objective optimisation design for brushless electrically excitated synchronous machines in electric vehicles

Design and Analysis of an Asymmetric Spoke and Delta-Shape Interior Permanent Magnet Synchronous Machine

This paper proposes a design of an asymmetric spoke and delta-shape interior permanent magnet (AIPM-P) synchronous machine for electric vehicles that use the magnetic-field-shifting (MFS) technique to improve the average torque and reduce torque ripples. The asymmetry of the AIPM-P is due to the asymmetric rotor structure, asymmetric permanent magnet (PM) placement, and asymmetric flux barriers (AFB). Due to this asymmetry, the MFS is utilized, which decreases the current angle difference between the peak PM torque ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{PM}$ </tex-math></inline-formula> ) and reluctance torque ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{r}$ </tex-math></inline-formula> ) components. In the delta-shape, the bar magnet helps reduce the d-axis inductance, which helps in increasing the reluctance torque, ultimately increasing synthetic torque. Furthermore, the combination of delta-shape and spoke shape PM makes the novel hybrid layer structure that improves the average torque. The proposed AIPM-P is then compared with the conventional designs in the literature having the same stator and rotor radius, with a 4-pole and 24-slot combination. The open circuit, on-load characteristics, efficiency, copper, and iron loss maps of the proposed and conventional designs are investigated and compared. Compared to the conventional designs, the proposed AIPM-P synchronous machine has high efficiency and a good torque profile, which is suitable for EV applications.

A New Analytical Thermal Model of Distributed Winding Wheel Machine for Electric Vehicles

Due to the complex boundary conditions of the thermal analysis method (AM), the error of the calculation results is large, and the lumped-parameter thermal network (LPTN) mostly focuses on the solution of the average temperature. This paper proposes a thermal analytical model for wheel-motor windings, which includes LPTN and AM to solve the problems of boundary condition extraction and maximum temperature solution in AM. The heat transfers between the end caps of electric vehicle wheels and the outside air are considered by the model. The node temperature of LPTN can be adopted as the boundary condition of the proposed analytical method to predict and calculate the maximum temperature and average temperature of the wheel motor and improve the accuracy of temperature rise calculation. To further analyze the winding temperature, the armature winding is divided into active winding and end winding for calculation respectively. In the calculation of active winding, based on the equivalent area method, the active winding and other materials are layered into a series of equal-width rectangular rings through a novel layered strategy. The compensated thermal resistance (TR) is introduced into the analytical model of end winding, and the accuracy of the end temperature solution is improved by the iteration of compensated TR. Finally, the effectiveness and correctness of the proposed analytical thermal model for motor temperature rise prediction are verified on a 2kW distributed double-layer winding wheel motor.

Inverter Design Considerations for Variable-Pole Induction Machines in Electric Vehicles

This article proposes a generalized inverter design framework for a variable-pole induction machine (IM). It quantifies the advantages of pole changing and a high number of inverter legs on converter efficiency and size. The framework is used to design an 18-leg drive that reconfigures a six-pole IM to four- and two-pole while increasing torque capability at maximum speed by a factor of 2.2 compared to a conventional 3-leg fixed-pole design. The framework also shows that a three-leg drive must be oversized by a factor of 1.5 to reach the same torque capability using an identical-sized machine. The proposed 18-leg drive has 50% less losses and requires 62% less dc-link capacitance compared to a 3-leg converter. The framework is used to propose a loss minimization method for the combined machine and converter, with pole count as an operational degree of freedom at partial load and high speed. As a result, variable-pole operation reduces combined machine and drive losses by up to 45% compared to a conventional three-leg drive with the same IM. An 18-leg experimental GaN-based 890 VA inverter driving a toroidally wound IM was designed, built, tested, and compared to a 3-leg inverter to validate the proposed framework.

Adaptive Controller of Bidirectional DC-DC Converter Based on Extreme Learning Machine for Electric Vehicle

Adaptive Controller of Bidirectional DC-DC Converter Based on Extreme Learning Machine for Electric Vehicle

Possibilities of Conventional PD Measurements with Non-Sinusoidal Waveforms for Electric Vehicles

Electrical traction machines in electric vehicles are normally fed by converters with DC link voltages up to 800 V. The resulting voltage pulses place particular stress on the insulating system of the drivetrain. In order to be able to investigate insulating material samples, e.g. twisted pair enameled wire, with voltages of different shapes and high frequency, a shielded experimentalsetup for the investigation of partial discharges (PD) at low voltages and high frequencies is presented. A medium frequency transformer with a frequency range up to 2500 Hz is used for this purpose, fed by a linear power amplifier on the primary side. The amplifier has a slew rate of 52 V/μs and is capable of sourcing various voltage waveforms such as sinusiodal, triangularor rectangular, with a maximum frequency of 30 kHz. Electrical PD measuring methods according to IEC 60270 as well as acoustic and optical measurement methods are applied for PD diagnosis. The experimental setup is intended to demonstrate the possibilities and limitations of conventional PD diagnostics for nonsinusoidal voltages. Focus is placed on the application of filters, the damping behavior of the step-up transformer and the rise times of the voltages.

Comparison of Different Winding Configurations for Dual Three-Phase Interior PM Machines in Electric Vehicles

In this paper, two dual three-phase winding configurations are compared based on the Toyota Prius 2010 interior permanent magnet (IPM) machine. It is found that the winding configuration with single-layer full-pitched (SF) windings can improve average torque and reduce torque ripple in constant torque range. The winding configuration with double-layer short-pitched (DS) windings has better torque performance in a constant power range. The electromagnetic performances of the two winding configurations when one winding set is excited and the other one is open-circuited are also compared. The DS winding configuration shows much better performance under this condition. Overall, the dual three-phase winding configuration with DS windings is preferred for dual three-phase IPM machines in electric vehicles. A Toyota Prius 2010 IPM machine equipped with DS windings was manufactured to verify the analyses presented in this paper.

Dimensioning of a permanent magnet synchronous machine for electric vehicles according to performance and integration requirements

AbstractFinding the optimum design of electrical machines for a certain purpose is a time-consuming task. First results can be achieved, however, with scaling known machine designs in length and turns per coil by means of analytical equations, while scaling in diameter requires finite element analysis (FEA), since electromagnetic properties change significantly. In this paper, the influence of diameter, length and turns per coil on the torque, power and efficiency of a permanent magnet synchronous machine (PMSM) are investigated in a sensitivity analysis. Furthermore, their impact on energy consumption in different drive cycles and different vehicle types is outlined. A highway car and a city car are compared in a highway cycle, a city cycle and the Worldwide Harmonized Light Vehicle test Cycle. The results describe significant differences in energy consumption for different machine designs in one application but also between different applications. This highlights the necessity to decide whether or not the powertrain should be optimized for a single purpose or for universal use.

Electromagnetic torque prediction and harmonic reduction of interior permanent magnet synchronous motor for electric vehicles using an analytical method

Interior permanent magnet synchronous motors (IPMSMs) have been widely used as drive machines in electric vehicles (EVs) due to their high torque density. However, the torque ripple of IPMSMs will result in severe noise and vibration. This paper proposes a new analytical method for electromagnetic torque prediction and harmonic reduction of IPMSM. On the basis of dq theory, an analytical model of electromagnetic torque is firstly established by taking the permanent magnet flux harmonics and the cross-coupling effect into consideration. And the specific sources and orders of torque harmonics are also determined. Then, the torque-angle characteristics are further studied. In particular, the permanent magnet (PM) torque and the reluctance torque are separated and quantitatively analyzed via the proposed analytical model. Finally, a theoretical method of reducing the specific order torque harmonic by PM shifting is derived and proposed from the perspective of avoiding resonance. The accuracy and effectiveness of the proposed analytical method are verified by finite-element analysis. The results show that the proposed analytical model is accurate enough to predict the electromagnetic torque performance of IPMSM. Moreover, the electromagnetic torque harmonics with specific orders can be effectively reduced by shifting the PM to an appropriate angle.

Design Optimization of Multi-Layer Permanent Magnet Synchronous Machines for Electric Vehicle Applications

This paper presents a comparison between two design methodologies applied to permanent magnet synchronous machines for hybrid and electric vehicles (HEVs and EVs). Both methodologies are based on 2D finite element models and coupled to a genetic algorithm to optimize complex non-linear geometries such as multi-layer permanent magnet machines. To reduce the computation duration to evaluate Induced Voltage and Iron Losses for a given electrical machine configuration, a new methodology based on geometrical symmetries and magnetic symmetries are used and is detailed. Two electromagnetic models have been developed and used in the design stage. The first model was the stepped rotor position finite element analysis called abc model which considered the spatial harmonics without any approximation of the waveform of flux linkage inside the stator, and the second model was based on a fixed rotor position called dq model, with the approximation that the waveform of flux linkage inside the stator was sinuous. These two methodologies are applied to the design of a synchronous machine for HEVs and EVs applications. Design results and performances are analyzed, and the advantages and drawbacks of each methodology are presented. It was found that the dq model is at least 5 times faster than the abc model with high precision for both the torque and induce voltage evaluation in most cases. However, it is not the case for the iron losses computation. The iron loss model based on dq model is less accurate than the abc model with a relative deviation from the abc model greater than 70% at high control angle. The choice of the electromagnetic model during the optimization process will therefore influence the geometry and the performances of the obtained electrical machine after the optimization.