Levitation Coil Research Articles

Heat load tests of superconducting magnets vibrated electromagnetically for the Maglev train

Superconducting magnets on Maglev trains vibrate due to harmonic ripples of electromagnetic flux generated by ground coils. Heat load caused by vibration in the magnet amounted to several tens of watts in the electromagnetic vibration test. This was mainly because a.c. loss was induced in the helium vessel housing the superconducting coil, due to relative vibration between the aluminium thermal shield and the coil. The heat load caused by vibration should be strictly restricted to less than 4W due to limited cryogenic refrigeration capacity. The heat load was tested using electromagnetic flux ripples for a superconducting magnet model of one coil which corresponds to 1 4 of an actual magnet. The flux ripples simulated the 6th harmonic of the actual ground levitation coil. Some ideas to reduce the heat load were tried for the magnet model, such as applying high resistance thermal radiation shielding, increasing rigidity of the vacuum vessel, and using high purity copper plating on the helium vessel. These ideas proved effective, and the maximum heat load due to vibration was held to less than 4 W per magnet for the one coil magnet model.

Development of a MAGLEV superconducting magnet for the Yamanashi test line in Japan: vibration characteristics and analysis for design

A high-performance and high-reliability magnetically levitated (MAGLEV) superconducting magnet (SCM) was developed. Its heat generation per unit time by the electromagnetic forces due to the spatially fifth ripple magnetic fields from levitation coils is under 2 W at the frequency range in which vehicles are levitated. The vibration mode of inner vessels that makes the largest contribution to heat generation in SCMs is clarified, the torsion mode. A modeling method to analyze SCM vibration, which considers the effect of the bogie frames of a vehicle, is examined, and heat generation in SCMs is calculated from the vibration of the inner vessel. Using the numerical analysis method, new SCMs combined with new bogie frames for the Yamanashi Test Line are designed. Good performance in vibration and heat generation of these SCMs is predicted by numerical analysis.

Magnetic Damping of the Electrodynamic Suspension Type Superconducting Levitation System

The damping characteristic of the bogie motion is one of the most important issues to be investigated in the superconducting magnetically levitated system based on the Electrodynamic Suspension (EDS). We have therefore studied the damping characteristics and the mechanism of magnetic damping. Electric circuits consisting of coil resistances and inductances can describe the electromagnetic behavior of the levitation system. By numerical calculation based on the electric circuit equations combined with the equations of motion, damping characteristics of the bogie are examined for the system consisting only of levitation coils and superconducting coils and also for the configuration with magnetic shielding structures incorporated. Furthermore, paying attention to the energy balance in the levitation and propulsion system when the bogie is forced to oscillate sinusoidally, we have investigated the relation between the input energy and the running speed and compared the waveforms of levitation force and bogie oscillation to consider the characteristics and the mechanism of the damping.

Initial fabrication of a micro-induction gyroscope

A planar coil design capable of levitating an aluminium rotor by electromagnetic induction is described. The coil is fabricated from Au onto a Si(001) substrate with a footprint size of 700 μm, and coil thickness and typical width of 1.3 μm and 50 μm respectively. The rotors are made from Al with a thickness of 12 μm and diameter of 400 μm. A maximum levitation height of 10 μm is measured with a coil excitation current of 800 mApk. This height is increased to 25 μm by the incorporation of a high permeability amorphous magnetic backing plane below the planar coils. Excellent quantitative agreement is observed between the predictions of modelling and experimental measurements of levitation height versus coil excitation current. The application of this levitated rotor to a wide range of applications, including a micromachined rotating gyroscope is described.

Dynamics of the bogie of a maglev system with guideway irregularities

This paper describes the stability of a bogie in the electrodynamic suspension system with superconducting magnets, especially in response to displacement of the levitation coils. The result of dynamic analysis indicates its stability with the displacement of coils which may happen most frequently; such as a longitudinal displacement and a vertical displacement. In addition, Cayley-Klein parameters are adopted for conversion of coordinates in this analysis in order to simplify it instead of Euler angles which are usually used in 3-dimensional analysis. All simulations in this paper are conducted with these parameters.

Determination of Hydrogen in Steel by Using a Levitation Melting Method

A new quantitative technique for determination of hydrogen in steels has been developed using levitation, which permits flotation and melting of samples by magnetic pressure under application of a high-frequency magnetic field to steel specimens. Steel samples are melted in a state of levitation in a flow of nitrogen gas. The discharged hydrogen gas is detected and measured quantitatively with a thermal conductivity detector. This method needs no crucible because the melting occurs in flotation. A cylindrical-shaped steel sample of 6 mm diameter and 6 mm length (about 1.5 g) was melted using the levitation melting technique. Radio frequency power of 1.5 kW with 200 kHz was applied to the levitation coil. Hydrogen was completely extracted within 1 min after melting. Working reference materials of stainless steel samples were analyzed in order to evaluate the present analytical method. The calibration curve showed an excellent linearity in a range of 0.4−6.7 μg/g, with a relative standard deviation of about...

Minimization of the induced current effects in the shields of SC coils in EDS-MAGLEV trains

In magnetically levitated transport systems of the electrodynamic type, eddy-currents in the shield of the on-board superconducting coils are caused by the harmonics of the magnetic field produced by the on-ground coils, in particular by the reaction field of the levitation coils. The paper presents a method to optimize the geometrical sizes of both the superconducting and the levitation coils, with the aim to minimize the field harmonic content on the shield. The method is based on the iterative application of analytical expressions of the flux density produced by the levitation coils. As an example of application, a given configuration is optimized according to the proposed technique; the shield eddy-current losses are calculated by means of a 3D FEM code for both the starting and the optimized configurations and the results are compared.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Persistent Current Analysis of Superconducting Coils in an Electrodynamic Suspension System

AbstractIn a superconductive electrodynamic suspension system, superconducting coils experience a space harmonic magnetic field generated by induced current in the levitation coils installed along the guideway. Current in a superconducting coil varies to keep the total magnetic flux constant when the coil is exposed in an external magnetic field. However, superconducting coil current was treated as constant in the conventional analysis because the electromagnetic forces can be estimated easily.The purpose of this paper is to determine the behavior of the persistent current in making reliable and tough superconducting magnets. A simple method to analyze fluctuating persistent current in a superconducting coil is proposed first. Calculated results for the normal running condition showed that the fluctuations of persistent current are less than 1 percent of the initially excited current for the sidewall levitation system, and less than 2 percent for the ground levitation coil system. Even when the null flux guidance cable is short‐circuited, the fluctuation is less than 5 percent. Considering that the magnetic shield effects by the conductive cryostat vessels were neglected in this analysis, the fluctuating magnetic field by levitation coils will never affect the stability for a superconducting magnet.

Consideration of the Excess Heat Capacity for the Evaluation of Mixing Enthalpies Measured by Levitation Alloying Calorimetry

A levitation alloying calorimeter (LAC) was developed by us and has been used frequently to measure the mixing enthalpies of high-melting binary liquid alloys. Performing a gradually alloying of small solid secondary samples into a liquid basis sample which is levitated in the electromagnetic field of a levitation coil, we were able to determine the mixing enthalpies containerless and economically in comparison with conventional calorimetric methods. An error occurs particularly in systems with intermetallic compounds because we have neglected the excess heat capacity during the evaluation. The presented mathematical method takes the excess heat capacity into account and results in a substantial improvement on the applicability of the LAC method

A new repulsive magnetic levitation approach using permanent magnets and air-core electromagnets

This paper introduces a new repulsive magnetic levitation approach using permanent magnets and air-core electromagnets as primary actuating components. The permanent magnets, which are attached to the bottom of a carrier, are repulsively levitated above and by oblong shaped electromagnets, which constitute one part of the guide tracks. Due to the lateral unstable nature of repulsive levitation, the stability of the levitated permanent magnets is regulated by another part of the guide tracks, electromagnetic stabilizers, which are strands of straight wires running through the entire length of the guide tracks above the levitation coils. A state feedback controller with integral compensator is designed for the stability control. The entire levitation system is divided into three subsystems: levitation, stabilization and propulsion. All the control works with respect to each subsystem are executed extrinsic to the carrier, i.e., there is no electrical circuit on board the carrier. The feasibility of this new levitation approach is confirmed successfully by a small scale demonstration system designed to transport a single silicon wafer in a microelectronic fabrication line. The wafer carrier is stably levitated 1.5 mm above the track surface with lateral air-gaps of 0.5 mm. Its maximum velocity is 22.2 cm/sec and the traveling range is 1 m. >

Preparation of amorphous alloys in Zr–Mo–Pd system

All boundary systems of the Zr–Mo–Pd system show at least one eutectic. This indicates the existence of low melting temperature (~1000°C) eutectic alloys in this ternary system, and is therefore directly related to the possibility of glass formation. Some amorphous and microcrystalline ternary samples were prepared via rapid solidification (~106 K s−1 ) in a splat cooling apparatus with a radio frequency levitation coil and a high velocity two piston arrangement driven by solenoids. To obtain the starting material, homogeneous Zr–Mo–Pd samples of differing composition were prepared via arc melting techniques. Some amorphous alloys have also been obtained in the Zr–Pd–(Si,B) systems.MST/1662

Persistent Current Analysis of Superconducting Coils in an Electrodynamic Suspension System.

In a superconductive electrodynamic suspension system, superconducting coils experience space harmonic magnetic field generated by induced current in the levitation coils installed along the guideway. Current in a superconducting coils varies to keep the total magnetic flux constant when the coil is exposed in an external magnetic field. However, superconducting coil current was treated as constant in the conventional analysis, because the electromagnetic forces can be estimated easily.The purpose of this paper is to know the behaviour of the persistent current to make reliable and tough superconducting magnets. A simple method to analyze fluctuating persistent current in a superconducting coil is proposed at first. Calculated results for the normal running condition showed that the fluctuations of persistent current is less than 1% of the initially excited current for the side-wall levitation system, and less than 2% for ground levitation coil system. Even when the null flux guidance cable is short-circuited, the fluctuation is less than 5%. Considering that the magnetic shield effects by the conductive cryostat vessels was neglected in this analysis, the fluctuating magnetic field by levitation coils will never affect stability for a superconducting magnet.

浮上式鉄道用超電導磁石の振動による熱負荷増

Superconducting magnets on Maglev trains vibrate due to harmonic ripples of electromagnetic flux generated by ground coils. Heat load caused by vibration in the magnet, made in 1990, amounted to several tens of watts in the electromagnetic vibration test. This was mainly because AC loss was induced in the helium vessel housing the superconducting coil, due to relative vibration between the aluminum thermal shield and the coil. The heat load caused by vibration should be strictly restricted to less than 4W due to limited cryogenic refrigeration capacity. The heat load has been tested using electromagnetic flux ripples for a superconducting magnet model of one coil which corresponds to 1/4 of an actual magnet. The flux ripples simulate the 6th harmonic of the actual ground levitation coil. Some ideas to reduce the heat load were tried for the magnet model, such as high resistance thermal radiation shield, high rigidity of vacuum vessel, high purity copper plating on the helium vessel. As a result, these ideas were effective, and the maximum heat load due to vibration was restrained to less than 4W per magnet for one coil magnet model.

Application of superconducting cable-in-conduit conductors to coil systems for Maglev vehicles

Significant system advantages result if the superconducting levitation and propulsion coils can be operated at temperatures higher than 4.2 K, which can be achieved with cable-in-conduit conductors (CICCs) using Nb/sub 3/Sn and supercritical helium as the working fluid. The authors compare the relative advantages of NbTi and Nb/sub 3/Sn for this application. They also discuss the system aspects surrounding the selection of operating temperature, current density and number of modules. The features of a suitable CICC Nb/sub 3/Sn conductor which has been manufactured are described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis of superconducting magnet (SCM)-ground coil interactions for EDS Maglev coil configurations

The performance of electrodynamic magnetic levitation systems is dominated primarily by the electromagnetic interactions between the onboard superconducting magnets (SCMs) and the normal levitation and propulsion coils situated on the guideway. Alternative designs are examined for coil configurations in terms of the resulting SCM-ground coil interactions. In particular, the modified null flux configuration and the ladder-on-box-beam approach are compared. Magnetic drag, levitation, and guidance forces are considered on an absolute and per (kg/m) of ground coil basis.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Levitation coil length optimization of a magnetically levitated train

AbstractAn experimental line of a magnetically levitated train (MAGLEV) using superconducting magnets (SCM) is now under construction in Yamanashi Prefecture. In the MAGLEV system, the levitation coils are mounted in the side walls. The induced current of the levitation coils generates magnetic flux that includes higher order harmonics. These harmonics generate eddy currents at the surface of the vacuum vessels of the SCM. Forces produced by interaction between the eddy current and the static magnetic field of the SCM cause evaporation of liquid helium, or SCM quenching in the worst case. The number of levitation coil layer is now restricted to one, but by removing the restriction, it is possible to reduce the amplitude of the harmonics of the magnetic flux. In this paper, the relationship of the flux amplitude to the levitation coil length is investigated; it is found that there is an optimum length at which the amplitude is minimized.

Characteristics of combined levitation and guidance eds maglev system

AbstractA levitation method has been introduced which uses 8‐shape levitation coils arranged on the vertical surface of the guideway. These coils can act as a guidance means as well as the levitation means. The characteristics of this system are examined using numerical examples and experimental data. The cables connecting right and left coils are not connected to a high‐voltage power source unlike the usual guidance system which is combined with propulsion. Thus the electric insulation of the cables is not a problem at present. Numerical examples show that the levitation characteristics of the combined levitation and guidance system are almost the same as in the system without the guidance function, and that it attains reduced running resistance with necessary guidance stiffness obtained. A test run was done at Miyazaki Test Line equipped with coils of this type arranged about 120 m, and the results show stable running and balanced displacement which agrees with calculated values.

Some amorphous alloys in Zr-Ru-Mo and Zr-Ru-W systems prepared by rapid solidification

All binary systems of the ternary systems Zr-Mo-Ru and Zr-W-Ru show at least one eutectic point. This indicates the existence of low melting eutectic alloys in these ternary systems (∼ 1200–1300°C). As starting materials, homogeneous Zr-Mo-Ru and Zr-W-Ru samples of different compositions were prepared by rapid solidification (∼106Ks−1) in a splat-cooling apparatus with a rf levitation coil and a high-velocity two-piston arrangement driven by solenoids. The possibility of obtaining alloys in amorphous state from low-melting areas of these ternary systems with the addition of boron or silicon has been investigated.

Characteristics of Combined Levitation and Guidance EDS Maglev System.

A levitation method has been introduced which uses 8-shape levitation coils arranged on the vertical surface of the guideway. These coils can act as a guidance means as well as the levitation means. The characteristics of this system are examined using numerical examples and experimental data. The cables connecting right and left coils are not connected to a high-voltage power source unlike the usual guidance system which is combined with propulsion. Thus the electric insulation of the cables is not a problem at present. Numerical examples show that the levitation characteristics of the combined levitation and guidance system are almost the same as in the system without the guidance function, and that it attains reduced running resistance with necessary guidance stiffness obtained. A test run was done at Miyazaki Test Line equipped with coils of this type arranged about 120 m, and the results show stable running and balanced displacement which agrees with calculated values.

Levitation Coil Length Optimization of a Magnetically Levitated Train.

Levitation Coil Length Optimization of a Magnetically Levitated Train.