Propulsion Coils Research Articles

R&D of on-board metal-insulation REBCO superconducting magnet for electrodynamic suspension system

Metal-insulation (MI) REBCO high-temperature superconducting (HTS) magnet has the advantages of short charging delay, low contact losses, and self-protection abilities, which shows important application prospects in many fields. Recently, Institute of Electrical Engineering, Chinese Academy of Sciences developed a prototype on-board MI HTS coil used for electrodynamic suspension (EDS) system working with an acceleration of beyond 8 g. To design a reliable engineering on-board magnet, specific Ic angle dependence data of short sample under different fields were fully considered to estimate the operating margin and losses accurately of the on-board magnet. A semi-analytical method, combination of the dynamic circuit method and finite element method, was used to analyze the dynamic electromagnetic force distribution inside the on-board magnet under motion state, in which the effect of the propulsion coils and the figure-eight-shaped coils were taken into considerations. Finally, a full-size MI double pancake racetrack coil was fabricated and tested in a liquid nitrogen bath. The test results meet the design requirements and verify the feasibility of the design, which provides an important reference for the experiment of on-board EDS with high acceleration in the future.

3-D Modeling of Current Decay in a Closed HTS Racetrack Coil Under Traveling Magnetic Fields

High temperature superconducting (HTS) magnets working in persistent current mode (PCM) have shown a superior potential in electrodynamic suspension (EDS) train applications. When exposed to the external traveling magnetic fields generated by the propulsion coils, the on-board HTS coils used as the secondary of synchronous motor will suffer a non-negligible loss resulting from dynamic resistance which is much larger than caused by joint resistance. In this work, we build a 3-D finite element model of a real scale HTS racetrack coil to predict its behaviour. In the modeling, homogenization technique and the symmetry plane are adopted for accelerating computation, and the proper boundary conditions are used for field-cooling excitation as well as applying traveling fields. Firstly, the effectiveness of the model has been validated by comparing with experimental results of a small prototype. Then based on the method, a real scale HTS racetrack magnet model with the symmetry modified as to adapt the EDS scenario is built for investigating the current decay property varying with the external fields. Moreover, the effect mechanism of the instantaneous AC loss on the current attenuation is deeply analyzed.

Improvement of the Propulsion Force by the Excitation Principle of the Propulsion Coil in the Permanent Magnet-HTS Hybrid Magnetically Levitated Transport System

Improvement of the Propulsion Force by the Excitation Principle of the Propulsion Coil in the Permanent Magnet-HTS Hybrid Magnetically Levitated Transport System

<b>Insulation Diagnosis with a Focus on Partial Discharge of the Propulsion Coils of the Superconducting Maglev</b>

<b>Insulation Diagnosis with a Focus on Partial Discharge of the Propulsion Coils of the Superconducting Maglev</b>

Calculation and Optimization of Propulsion Force of a Real-Scale REBCO Magnet for EDS Train

Electrodynamic suspension (EDS) train has the unique advantages of excellent levitation and guidance stabilities, large levitation gap, and so on. All of these merits make it a promising candidate for the future ultra-high-speed transportations, in which the high-temperature superconducting (HTS) linearly synchronous driving motor (LSM) plays an important role because of the decrease of energy consumption of HTS magnet. This paper, which serves as a fundamental study on the HTS synchronous driving system of EDS train, is aimed to calculate the propulsion force of LSM and optimize the propulsion fluctuation. First, in order to define the operating current of LSM, the critical current of a real-scale REBCO coil was numerically estimated using the so-called T-A model. Second, based on the Neumann formula and virtual displacement method, an analytic model to estimate the propulsion force of LSM was established and verified by comparing results with a finite-element method (FEM) numerical model. Finally, by resorting to the validated analytic model, the geometric parameters of propulsion coil were optimized, and then using the optimal parameters, the maximum electromagnetic forces of LSM under different operating conditions of EDS train were calculated. It was found that the linearly driving system inherently keeps robust driving stability to the lateral and normal displacements.

Non-Contact DC Electromagnetic Propulsion by Multipole Transversal Field: Numerical and Experimental Validation

This paper describes the numerical and experimental validation of a novel non-contact dc electromagnetic propulsion concept. In the proposed approach, a propulsion coil carrying a dc current is surrounded by a dc transversal multipole field created inside of a launch tube. The interaction between the transversal dc magnetic field and a dc propulsion coil results in the generation of axial (thrust) force with no need of sliding contacts. This paper describes a numerical assessment of the field-current-force interactions based on both analytical calculations and finite elements, and the corresponding validation experiments. The experiments demonstrate the generation of contactless axial (thrust) force in a dc launch coil using a dc transversal multipole field, and provide a benchmark for the model-based prediction of the field-current-force interactions. Partial magnetic shielding of the propulsion coil is used to selectively attenuate the magnetic field experienced by the thrust coil in a way that a net thrust force is achieved. Experimental measurements confirmed that it is indeed possible to generate contact-free thrust force on a dc propulsion coil using a dc multipole magnetic field, and the measured values of thrust force are in good agreement with the corresponding predictions.

Propulsion Characteristics Using Pinned Flux of the HTS in the Permanent Magnet–HTS Hybrid Magnetically Levitated Conveyance System

The hybrid magnetically levitated carrying system has been developed. In this system, the pinning force of the high-temperature superconductor (HTS) achieves stable levitation and guidance without control. Repulsive force caused by the permanent magnets is used to support the load weight of the carrier. The interaction between the permanent magnet and the air core copper coils (propulsion coils) generates propulsion force. To increase the propulsion force, propulsion coil pitch is changed. In a previous research study, only flux of the permanent magnet is used for propulsion. Hence, the flux of the HTS for levitation and guidance is also used for propulsion. From the experimental results, propulsion force becomes about 131% larger than that of the conventional excitation method. There is no influence on the pinning characteristics for levitation and guidance by using the pinned flux of the HTS for propulsion.

Study on control method of running velocity for the permanent magnet–HTSC hybrid magnetically levitated conveyance system

We have developed the magnetically levitated carrying system. In this system, pinning force of high temperature bulk super conductor (HTSC) is used for the levitation and guidance. Four HTSCs are installed on the carrier. The magnetic rail is set on the ground, and flux from the magnetic rail is pinned by HTSCs. To increase levitation force, repulsive force of the permanent magnet is used. The hybrid levitation system is composed. The permanent magnet is installed under the load stage of the carrier. Repulsive force by the permanent magnet between the load stage on the carrier and the magnetic rail on the ground is used to support the load weight. Levitation and guidance one by pinning effect of the YBaCuO HTSC in the carrier is used to levitate the carrier body. The load stage is separated from the carrier flame and can move freely for vertical direction levitation. For the propulsion system, electromagnet is installed on the surface of the magnetic rail.In this paper, control method of running velocity of the carrier is studied. Propulsion force is given as follows; Air core copper coils are installed on the magnetic rail. Interaction between current of these coils and permanent magnets on the carrier generates propulsion force. Running velocity is controlled by current of the propulsion coils. It is also changed by position of the carrier and the load weight. From the results, stability of the propulsion system is given, and propulsion characteristics are improved.

Multimission Electromagnetic Launcher

The multimission electromagnetic launching system employs induction coilgun technology. The system is composed of a launcher, electromagnetic pulse power supply, control system, support equipment, and multiple launch packages. The goal of the system is to extend countermeasure decoy effectiveness and expand electromagnetic launch missions. A series of concept feasibility demonstrations were conducted in 2005 and 2006. Concept feasibility demonstrations for the launcher and pulse power supply were conducted in 2005. Launch package concept feasibility demonstrations for a countermeasure decoy were conducted in 2006. In 2007 and 2008, we developed and tested prototype propulsion coil technology to address tactical application capabilities. Results will be discussed for all series of demonstrations. Lockheed Martin MS2 has performed the system concept feasibility demonstrations and prototype testing with support from Sandia National Laboratories.

Durability Evaluation Tests of Mold Resin for Ground Coil

The superconducting magnetically levitated transportation (Maglev) system requires ground coils suitable for long-term outdoor use along the entire length of the guideway, meaning that the assurance of stable performance and high reliability is an important consideration in developing these coils. Durability verification testing from the level of the component materials to the actual product on the assumption of commercial service is therefore necessary to guarantee total reliability. We performed flexural fatigue tests using specimens made of the epoxy resin used for actual propulsion coils. The results were used to create a fatigue limit diagram as well as a diagram to verify Miner's Law. We then confirmed the correlation between the color difference and the flexural strength by comparing the outdoor exposure test results with those of accelerated artificial exposure testing.

Proposal of permanent magnet repulsive maglev transportation system: possibility of automobile with magnetic levitation

AbstractThis paper describes a maglev transportation system for automobiles. The track is an array of permanent magnet blocks, and the levitating body is the bedplate which consists of permanent magnet plates, propulsion coils, levitation coils, and guidance coils. The feature of this system is that an automobile equipped with the bedplate is free to approach into the track or to swerve from the track by using four wheels with the lift. The force acting on the levitating body is calculated on the assumption that each permanent magnet can be expressed as a surface current. From the calculation results, it is proven that an automobile of 4.35 m length, 1.8 m width, and 1700 kg weight can run at a speed of 500 km/h against the air resistance force of 3704 N on the condition that the battery has an output of 337.5 V and a capacity of 190 Ah. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 65– 76, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20491

Frequency Characteristics of the MAGLEV Double-layered Propulsion Coil

The MAGLEV (magnetically levitated vehicle) is now well along in development testing at Yamanashi Test Line. The MAGLEV power source needs to supply a variable voltage and variable frequency to propulsion coils, which installed on outdoor guideway. The output voltage of the electric power converter contains many higher harmonics, which causes many troubles such as inductive interference. Accordingly, it is necessary to clarify the frequency characteristics of the propulsion coils and the power feeding circuit. In view of this situation, experiments and the theoretical analysis concerning the frequency characteristics of the propulsion coils with single-layer arrangement and the power feeding circuit at Miyazaki Test Line had been performed by the author. But the arrangement of the propulsion coils had been changed in Yamanashi Test Line from the single-layered coils to the double-layered coils for the stability of the super-conducting magnet on board. Thus, experiments and investigations concerning the frequency characteristics(resonance characteristics)of the propulsion coils with double-layer arrangement at Yamanashi Test Line have been performed but a theoretical analysis had not been done enough. A theoretical analysis was therefore done in this paper by applying the inverted L equivalent circuit with mutual inductance and capacitance to the propulsion coil, from which the positive and zero phase characteristics of the double-layered propulsion coils were analyzed.

Proposal of Permanent Magnet Repulsive Maglev Transportation System-Possibility of Automobile with Magnetic Levitation-

This paper describes a maglev transportation system for automobile. The track is an array of permanent magnet blocks, and the levitating body is the bedplate which consists of permanent magnet plates, propulsion coils, levitation coils and guidance coils. The feature of this system is that the automobile equipped with the bedplate is free to approach into the track or to swerve from the track by using four wheels with the lift. The force acting on the levitating body is calculated on the assumption that each permanent magnet can be expressed as a surface current. From the calculation results, it is proven that the automobile of 4.35m length, 1.8m width and 1700kg weight can run at speed of 500km/h against the air resistance force of 3704N on the condition that the battery has an output of 337.5V and a capacity of 190Ah.

Partial Discharge in Medium Voltage PWM Propulsion Coils

Evaluations of partial discharge (PD) in 4160 V propulsion coils have been conducted to understand the impact of inverter drives on electric motors for the planned U.S. Navy “electric” ships. The medium voltage (MV) PD evaluation “testbed” was designed and tested, and the influence of voltage level, voltage rise-time, switching frequency and temperature on the generation of PD was determined by optical and electrical PD detection methods. This article describes the design of the testbed, and the process of characterizing PD conditions comprehensively based on the above four parameters, representing a drive system consisting of an inverter and a high torque, low speed motor. Comprehensive results and analyses are presented, based on the evaluation of 30 coils from two U.S. Navy coil manufacturers, which included both inverter-duty and non-inverter duty coils, resulting in over 7000 tests.

Surge Characteristics of Propulsion Coils Including Mutual Coupling for Maglev

The Maglev system employs a linear synchronous motor (LSM) with the primary side on the ground, and uses a combined levitation-guidance system and double-layered propulsion coils. To analyze electric surge propagation, we measured the surge propagation between propulsion coils. We also set up simulation models and simulated the surge propagation by using the Electro-Magnetic Transients Program (EMTP). It was found that the measured values agreed well with the values simulated by EMTP. Therefore, it was verified that the proposed surge propagation models for simulation were very useful to estimate the surge propagation of coils used for Maglev.

Design of guidance system for superconducting maglev vehicle using propulsion coils

AbstractSuperconducting magnetically levitated vehicles have guidance coils that produce vehicle guidance forces using a null flux coil connection. However, the resulting forces do not have sufficient damping forces to suppress lateral vibration of the vehicle. Even though the experimental system has some magnitude of damping, it is still unsatisfactory. Moreover, since the guidance forces are very weak at low speeds, the minimum levitating speed is limited. The paper proposes a guidance method using LSM armature coil currents. When the currents are decomposed into the dq frame variables so that the d‐axis is assigned to the field axis, the d‐axis component of the currents generates lateral forces. The lateral forces of the vehicle are formulated, and the guidance force coefficient is defined. In addition, the author presents a design formula for a guidance regulator system that employs a dynamic compensator using a feedback signal of lateral displacement. The calculated results show that the guidance regulator system works as intended. © 2001 Scripta Technica, Electr Eng Jpn, 137(2): 44–51, 2001

Design of Guidance System for Superconducting Maglev Vehicle using Propulsion Coils

The superconducting magnetically levitated vehicle has guidance coils that produce vehicle guidance forces according to a null flux principle. However, the expected forces dont have significant damping forces to suppress a lateral vibration of the vehicle. Even though the experimental system has some magnitude of damping, it is still small. Moreover, since the guidance forces are very weak at low speeds, the minimum levitating speed is limited. The paper proposes a guidance method using LSM armature coil currents. When the currents are decomposed into dq frame variables so that the d-axis is assigned to the filed axis, the d-axis component of currents generates the lateral forces. The lateral forces of the vehicle are formulated, and the guidance force coefficient is defined. And the author shows the design formula of the guidance regulator system that employs a dynamic compensator using a feedback signal of lateral displacement. The calculated results show that the guidance regulator system works very well as we specify.

Insulation characteristics of XLPE cables for high frequency voltage with a PWM inverter

The development of feeder cables is being advanced for use in supplying power to propulsion coils to realize the Yamanashi experimental lines of a superconducting magnetic levitation railway (Maglev). A step voltage waveform is applied to the XLPE insulation of feeder cables by an inverter in which high frequencies are superimposed on the basic commercial frequency. The authors devised electrical testing equipment that can output such specific waveforms, and they investigated the effect of such waveforms on the insulation properties of XLPE cable, the breakdown characteristics of the model cables, and their long-term characteristics. As a result, it was learned that the insulation breakdown depends on the voltage waveform peak value and that the long-term characteristics are determined by the basic frequency. This knowledge will be useful for the insulation design of the feeder cable system of the Yamanashi experimental line. © 1999 Scripta Technica, Electr Eng Jpn, 129(2): 31–39, 1999

Insulation characteristics of XLPE cables for high frequency voltage with a PWM inverter

The development of feeder cables is being advanced for use in supplying power to propulsion coils to realize the Yamanashi experimental lines of a superconducting magnetic levitation railway (Maglev). A step voltage waveform is applied to the XLPE insulation of feeder cables by an inverter in which high frequencies are superimposed on the basic commercial frequency. The authors devised electrical testing equipment that can output such specific waveforms, and they investigated the effect of such waveforms on the insulation properties of XLPE cable, the breakdown characteristics of the model cables, and their long-term characteristics. As a result, it was learned that the insulation breakdown depends on the voltage waveform peak value and that the long-term characteristics are determined by the basic frequency. This knowledge will be useful for the insulation design of the feeder cable system of the Yamanashi experimental line. © 1999 Scripta Technica, Electr Eng Jpn, 129(2): 31–39, 1999

Surge Characteristics of Propulsion Coils Including Mutual Coupling for Maglev

A superconducting magnetic levitation system (Maglev) employs a linear synchronous motor (LSM) with primary side on ground. In the system, a combined levitation and guidance system arranging propulsion coils on the surface of the sidewall is used. Also, propulsion coils are electro-magnetically coupled to each other because they are attached in double layers. Therefore, propulsion coils on the both sidewalls are electro-magnetically coupled with the combined levitation and guidance system. This means that the surge characteristics of the system will be very complicated.As one of the analysis of the electric surge of such an electro-magnetically complicated system of Maglev, we measured the surge between propulsion coils and simulated it using EMTP (Electro-Magnetic Transients Program) in consideration of mutual coupling between coils. After confirming the agreement of the simulated results and the experimental results, characteristics for the practical large system such as Yamanashi Test Line are discussed.