Jian Xun Jin

Measurement and Modeling of Rotational Core Losses of Soft Magnetic Materials Used in Electrical Machines: A Review

In many situations, for example, in the cores of a rotating electrical machine and the T-joints of multiphase transformers, the magnetic flux varies with time in terms of both magnitude and direction, i.e., the local flux density vector rotates with varying magnitude and varying speed. Therefore, it is important that the magnetic properties of the core materials under various rotational magnetizations be properly investigated, modeled, and applied in the design and analysis of electromagnetic devices with rotational flux. Drawing from the huge amount of papers published by various researchers in the past century, this paper presents an extensive survey on the measurement and modeling of rotational core losses of soft magnetic materials used in electrical machines, particularly from the view of practical engineering application. The paper aims to provide a broad picture of the historical development of measuring techniques, measuring apparatus, and practical models of rotational core losses.

High-Temperature Superconducting Linear Synchronous Motors Integrated With HTS Magnetic Levitation Components

High-temperature superconductors (HTSs) including HTS bulks and tapes have potential applications in linear motion drive and magnetic levitation/suspension systems generating substantial advantages over conventional ones. When an HTS linear motor is integrated with an HTS magnetic suspension subsystem, it can inherit both merits of HTS linear motion drive and HTS magnetic suspension simultaneously and can be applied into various fields, such as the maglev and electromagnetic aircraft launch systems (EMALSs). Based on different HTS aspects and arrangements, three modes of HTS linear synchronous motor (HTSLSM) integrated with HTS magnetic suspension subsystems have been proposed in this paper. To verify the modes for the design of a practical HTSLSM, the structural features of these systems are described, the magnetization characteristics to obtain HTS bulk magnets, the trapped-field attenuation characteristics of the HTS bulk magnet exposed to external traveling field, and the magnetic field distribution characteristics for different permanent-magnet guideways have been studied with experimental verification. Based on the study, a demonstration prototype of a single-sided HTSLSM integrated with HTS magnetic suspension subsystems has been developed. Its performance and thrust characteristics have been obtained by experimental measurements and compared with theoretical results. With regard to practical applications, two modes of double-sided HTSLSM integrated with HTS magnetic suspension subsystems have been designed for the maglev and EMALS, respectively, and then, the 2-D finite-element-analysis models for the HTSLSMs were built to analyze their performance characteristics. The comprehensive simulations and experimental results constitute a framework for the structural and electromagnetic design of the HTSLSM integrated with HTS magnetic suspension for practical applications.

Design and Analysis of a Prototype Linear Motor Driving System for HTS Maglev Transportation

High temperature superconductors (HTSs) can produce a strong magnetic levitation force with self-stabilizing feature and hence have attracted much attention for applications in maglev transportation systems. For the linear motion of transportation, a linear drive is an obvious advantage. This paper presents the design and analysis of a permanent magnet (PM) linear synchronous motor for driving a small-scale prototype vehicle with PM-HTS bulks used for the levitation. The linear motor consists of PMs on the vehicle sides and stator windings in the slots of side tracks. The three phase windings are supplied by a 3-phase inverter, and are controlled with a brushless DC control scheme. Analysis and calculation details of magnetic fields and driving force about the motor prototype are presented.

Performance Characteristics of an HTS Linear Synchronous Motor With HTS Bulk Magnet Secondary

A single-sided high-temperature superconducting (HTS) linear synchronous motor (HTSLSM) with an HTS bulk magnet array as its secondary has been developed, and a split pulse coil magnetization system is used to magnetize the secondary HTS bulks with alternating magnetic poles. The electromagnetic parameters of the HTSLSM have been calculated to verify its performance. The HTSLSM is incorporated with a developed control system based on the voltage space vector pulsewidth modulation strategy implemented by a computer-software-controlled platform. A compositive experimental testing system has also been developed to measure the thrust and normal force of the HTSLSM. The traits of the thrust and normal force have been comprehensively identified experimentally, and the results from the experiments and analysis would benefit the electromagnetic design and the control scheme development for the HTSLSM.

Cryogenic Power Conversion for SMES Application in a Liquid Hydrogen Powered Fuel Cell Electric Vehicle

Cryogenic power conversion for superconducting magnetic energy storage (SMES) application in a liquid hydrogen (LH2) powered fuel cell electric vehicle (FCEV) is investigated. Principle and operation strategy of the SMES-based onboard energy system are presented for various operational models. A typical FCEV system equipped with a 720-kJ SMES device is conceptually designed and theoretically modeled with a bridge-type cryogenic chopper, which consists of four metal-oxide- semiconductor field-effect transistors (MOSFETs) cooled by low-temperature gas hydrogen (GH2). The bridge-type cryogenic chopper has higher energy storage and utilization efficiencies than the conventional one because the MOSFETs have much less thermal loss compared with normal operations of the MOSFETs and diodes. Both the start-up time and the regenerative braking time of the FCEV are significantly reduced with the introduction of the SMES. The design and tests of an experimental energy exchange prototype are also presented to verify the feasibility of the proposed high-efficiency SMES system incorporated with the FCEV.

High-Frequency Magnetic-Link Medium-Voltage Converter for Superconducting Generator-Based High-Power Density Wind Generation Systems

Recent advances in solid-state semiconductors and magnetic materials have provided the impetus for high-frequency magnetic-link-based modular medium-voltage power conversion systems, which would be a possible solution to reduce further the weight and volume of superconducting generator-based wind generation systems. To verify this new concept, in this paper, a laboratory prototype of 5 kVA high-frequency magnetic-link modular power conversion system is developed for a scaled down 1.2 kV grid application. The design and implementation of the prototyping, test platform, and the experimental results are analyzed and discussed. It is expected that the proposed new technology will have great potential for superconducting generator-based wind farm applications.

HTS Power Devices and Systems: Principles, Characteristics, Performance, and Efficiency

As the critical barriers to advanced high-temperature superconducting (HTS) device technologies are overcome, practical HTS devices and systems have been enabled and become available for commercial application. In identifying the applicability of various HTS devices, their operation principles, characteristics, performance, and efficiency are fundamental. Consequently, the corresponding verification of a wide range of HTS devices, especially the HTS power devices and their system technologies, has been comprehensively carried out, and the analytical results are presented in detail towards their practical applications.

Characterization of Partial Discharge With Polyimide Film in

High temperature superconducting (HTS) cable has now reached the stage where their application in power systems is in the process of being implemented. Liquid Nitrogen (LN2) and polyimide film have been used as a coolant and insulation in HTS cable systems. Partial discharge (PD) events may lead to material degradation and total breakdown. PD testing is an important quality check for the insulation of HTS cable. Thus it is necessary to consider PD for the insulation testing in LN2 which is generated in void defects of the insulation layers. The PD characterizations of polyimide film in different defects were investigated under 50 Hz AC voltages in LN2 and at room temperature (298 K). The results show that the number of discharges and the discharge quantity increase with the increasing of the applied voltage and the defect size. The PD inception voltage decreases when the void defect diameter enlarged and it is higher in LN2 than that at room temperature. The maximum field strength for HTS tape insulation increases with the defect close to the tape boundary and the addition of contaminant relative permittivity. Obtained results at cryogenic temperature provide necessary information for insulation design and pre-shipment inspections of HTS cable system.

\hbox{LN}_{2}

The battery lifetime of electric vehicles (EVs) has significant impacts on the development and popularization of EVs. A method with superconducting magnetic energy storage (SMES) to stabilize the EV charging system voltage to improve battery life and charge efficiency on a smart grid is presented. In order to verify the influence that the controlled SMES improves the system transient stability, situations under load fluctuation and fault, and the SMES capacity for system compensation have been investigated. The results obtained from the analysis indicate the effectiveness of compensating the instantaneous voltage dip in the grid and improving the power system quality.

Considering High Temperature Superconducting Cable Insulation

A superconducting magnetic energy exchange (SMEE) model based on a circuit-field-superconductor-coupled method is presented. The objective power system problems to be solved, e.g., power and load fluctuations, are transformed into equivalent energy exchange demanding values for the superconducting coil used in a superconducting magnetic energy storage (SMES) device. With the model, the buffering effects for the external power and load fluctuations and the superconducting properties of the superconducting coil itself can be obtained equivalently for optimizing and evaluating the designed SMES device. Four coil-current-dependent formulas are derived to estimate the hysteresis loss, coupling current loss, eddy current loss, and flux flow loss of the superconducting coil under different energy exchange operation conditions. A case study has been carried out using a Bi-2223 coil. The obtained results verify the effectiveness of the SMEE model and its feasibility for practical applications.