Silong Li

Partial Irreversible Demagnetization Assessment of Flux-Switching Permanent Magnet Machine Using Ferrite Permanent Magnet Material

This paper investigates the partial irreversible demagnetization characteristics of magnets in flux-switching permanent magnet (FSPM) machines. Two different partial demagnetization mechanisms in the FSPM machines are modeled and demonstrated. The 2-D finite-element analysis (FEA) results for a baseline 10 kW 15 kr/min ferrite FSPM machine verify the validity of the proposed partial demagnetization model. Performance degradation due to demagnetization is evaluated for the baseline machine based on the FEA results. This paper also proposes a novel design to enhance the demagnetization withstand capability. This research reveals the most vulnerable region of the magnet to irreversible demagnetization in the FSPM machines. It also provides a guideline for developing demagnetization withstand capability improvement techniques.

Analysis of flux switching permanent magnet machine design for high-speed applications

The purpose of this paper is to contribute to the high-speed aspect of flux switching permanent magnet machine by performing detailed electromagnetic design, performance evaluation, and trade-off comparisons. Topologies with multiple numbers stator slot/rotor pole combinations are analyzed, and their challenges for high-speed operation are discussed. The topology with 12 stator slots and 10 rotor poles is analyzed in detail including loss characterization. Properties of iron loss, especially the eddy current loss, are analyzed using fast Fourier transformation. Magnet eddy current loss is studied at high-speed conditions for neodymium magnets. Axial magnet segmentation is found to be effective for reducing the magnet eddy current loss. Windage loss of the rotor also is estimated using analytical methods and it cannot be neglected for high-speed operations.

High-Speed Electric Machines: Challenges and Design Considerations

High speed electric machines have been widely used in many applications nowadays and are gaining more attention. However, many special design challenges exist for HSEMs. This paper aims to discuss major challenges and design considerations for HSEMs. Four different loss components of high speed design are discussed and the methods to reduce each loss component are elaborated. Bearing options for HSEMs are compared. In addition, the rotor dynamics and thermal challenges are discussed in detail, following with some design suggestions and considerations.

Efficiency characterization and thermal study of GaN based 1 kW inverter

Rapid advancement of gallium nitride (GaN) based device technologies enables the possibility to design inverters that have superior performance capabilities compared to Si-based inverters. It is prevalently acknowledged that GaN-based switching devices outperform the Si-based counterparts in many aspects such as lower power consumption, and faster switching frequencies. GaN devices will benefit many applications such as hybrid and plug-in electric vehicles, solar power inverters, industrial motor drives, and aerospace. Nevertheless, the superiorities of GaN devices in inverter design have not been fully explored by researchers, and the purpose of this paper is to evaluate the high-efficiency capabilities of inverters that can be achieved using these new devices and the resulting benefits on the thermal aspect. As a case study, 1 kW GaN FETs inverter is considered. Loss and efficiency analysis is performed under various load conditions, and the requirements on heat sink for various ambient temperatures are specified according to the loss values obtained. Analysis results are compared with conventional Si-based inverters.

Performance Assessment of High-speed Flux-switching Permanent Magnet Machine Using Ferrite and Rare Earth Permanent Magnet Materials

Abstract This article presents the investigation and comparison of the capabilities and characteristics of high-speed flux-switching permanent magnet machines using ferrite and rare earth permanent magnet materials. Special design considerations for ferrite flux-switching permanent magnet machines under high-speed operation are proposed. Two ferrite and one NdFeB flux-switching permanent magnet machines, rated at 10 kW and 15 krpm, were designed for performance assessment. Various machine performances, including torque characteristics and loss distribution, are compared. In addition, the risk of partial demagnetization and the performance degradation due to partial demagnetization are also investigated. This research reveals several promising characteristics of the ferrite flux-switching permanent magnet machine, such as lower total loss, negligible magnet eddy current loss, and better cooling potential. The results also show the possibility of designing a high torque density ferrite flux-switching permanent magnet machine, which is comparable to the NdFeB flux-switching permanent magnet machine, taking advantage of the flux concentrating effect.

Driving Toward Accessibility: A Review of Technological Improvements for Electric Machines, Power Electronics, and Batteries for Electric and Hybrid Vehicles

Electric and hybrid vehicles continue to demand a considerable share of the automotive market. This movement has been enabled by the recent technological improvements in the areas of electric motors, power electronics, and energy storage. While many electric vehicles (EVs) are on the market, they are not as cost competitive as conventional vehicles, and affordable cost is necessary for large-scale market penetration. For this to become a reality, continued research is needed to develop new cost-efficient technologies. This article presents the metrics and benchmarks used to gauge the performance of various electric drivetrains. In addition, current state-of-the-art technologies are presented in terms of these metrics as well as the future goals and trends in the industry. With ongoing development, the market for electric and hybrid vehicles will continue to increase.

Comparative Analysis on Conducted CM EMI Emission of Motor Drives: WBG Versus Si Devices

Silicon carbide (SiC) MOSFETs and gallium nitride (GaN) high-electron mobility transistors are perceived as future replacements for Si IGBTs and MOSFETs in medium- and low-voltage drives due to their low conduction and switching losses. However, it is widely believed that the already significant conducted common-mode (CM) electromagnetic interference (EMI) emission of motor drives will be further exacerbated by the high-speed switching operation of these new devices. Hence, this paper investigates and quantifies the increase in the conducted CM EMI emission of a pulse width modulation inverter-based motor drive when SiC and GaN devices are adopted. Through an analytical approach, the results reveal that the influence of dv/dt on the conducted CM emission is generally limited. On the other hand, the influence of switching frequency is more significant. Lab tests are also conducted to verify the analysis.

Evaluation of torque compensation control algorithm of IPM machines considering the effects of temperature variations

For automotive applications, accurate torque production capability and high efficiency of the traction motor is very important. However, the performance of widely used interior permanent magnet (IPM) machines is influenced by temperature variations, and temperature variations of the magnets in automotive applications can be profound. In this paper, the state-of-the-art torque compensation control methods of IPM machines in the literature are reviewed. The methods for torque error estimation due to temperature variation are classified. In addition, the methods for adjusting the operating points of IPM machines to maintain torque production accuracy and high-efficiency operation are also overviewed. The advantages and disadvantages of each algorithm are described and compared in detail. This paper facilitates the development of high performance and robust IPM machine drive systems for the automotive industry.

Analysis of temperature effects on performance of interior permanent magnet machines

The purpose of this paper is to analyze and investigate the influence of temperature variation on the characteristics and performance of interior permanent magnet (IPM) machines. The impact of temperature variation on the materials of IPM machines is discussed to show the sources of performance variation. The flux linkages and torque output capability variation as functions of the temperature of are analyzed and discussed. The paper also shows the influence of temperature variation on key IPM machines performance including constant torque curves, voltage limit ellipses, maximum torque per ampere and maximum torque per volt trajectories and torque-speed curves. The results and trends shown in this paper set a foundation for developing control algorithm which takes the temperature effects into consideration, especially in the applications where operating temperature varies significantly.

Core loss estimation of high speed electric machines: An assessment

High speed electric machines have been gaining significant interest over the last several years. This is mainly due to several advantages including increased power density and lower cost. High speed machines can allow for the elimination of gear box to achieve higher reliability and reduced maintenance of the full drive system. One of the challenges with designing high speed machine is accurate estimation of core loss. This paper will introduce both opportunities and challenges of estimating core loss for high speed electric machines. First, this paper will summarize core loss characterization and modeling based on physical and mathematical formulation. The limitation of classical Steinmetz equation is explained and a modified Steinmetz equation with variable coefficients is presented to improve accuracy of the core loss estimation for wide frequency and flux density range. Several contributing factors are also reviewed for estimation of core loss with consideration of arbitrary excitation waveform, flux density distribution, and the skin effect. This paper explains a core loss model for permanent magnet electric machines and discusses the dependency of core loss on machine dimensions as well. Finally, future opportunities are suggested for core loss estimation of high speed machines.