Coil Assembly Research Articles

High Frequency Approaches for LTCC Based Sensors

Low temperature co-fired ceramics (LTCC) have been developed for RF and microwave circuits for a number of applications (i.e. cell phones and wireless systems). The same attributes that make LTCC an important technology for telecommunications are also important for sensors. Compact three-dimensional architectures with low dielectric loss materials are available with LTCC technology. The underlying electric and magnetic responses of materials in the RF and microwave frequency ranges will be discussed and these unique responses can be exploited in a sensor system. Gases, liquids and solids have unique dipolar responses in the RF and microwave ranges. For example, the dielectric relaxation of water has been investigated in water/starch mixtures. Classic dipolar relaxation of water occurs at 30GHz and additional relaxation mechanisms have been found in the 1–10 GHz range because of the starch gelation process. These relaxations could be the basis for a sensor system to monitor the gelation of food starches. In addition, miniature coil assemblies for magnetic resonance imaging (MRI) systems with operation in the 300 MHz to 850 MHz range will be presented. These types of coils with additional passive components are envisioned in a LTCC-based circuit topology.

A Study on the Shape of Iron-Core for a Hybrid Electro-Magnetic Suspension System

This paper deals with the shape design of the iron-core of a hybrid EMS (electro-magnetic suspension) system. A proto-type hybrid EMS system was developed by Yonsei University in 2010 [1], [2]. It is the first step of study on fundamental technology for advanced railroad systems development. The hybrid EMS system requires cooling systems because it uses superconducting magnets [3], [4]. These cooling systems can influence costs to making and operating the hybrid EMS system. Therefore, a study to reduce the number of cooling systems needs to be carried out in order to economically commercialize the hybrid EMS system. In this paper, a method that reduces the number of cooling systems of the hybrid EMS system was proposed. To achieve this, a small-scale iron-core and coils assembly was fabricated. Using this system, characteristics of levitation force according to the structure of the iron-core was evaluated. Also, numerical analysis using the FEM tool in order to evaluate the levitation force and net force of a full-scale model was performed. This paper can be expected to suggest useful data for the design of a hybrid EMS system.

Modeling of Electrodynamic Zero-Net Mass-Flux Actuators

electrodynamic zero-net mass-flux (ZNMF) actuator for flow control applications. The electrodynamic actuation schemeemploysamagneticassemblytoestablisharadialmagnetic fieldpatternwithanimbeddedcurrent-carrying coil winding. The coil is attached to a composite diaphragm having a rigid center boss and compliant outer annular region. The magnetic field acting on the coil assembly is modeled using a one-dimensional magnetic circuit. The composite diaphragm is modeled as a transversely isotropic, annular clamped plate. An overall lumped-element electromechanical system model is obtained by combining previously developed lumped models of the cavity/neck structures with lumped models for the composite diaphragm and electrodynamic actuation. The complete lumpedelement model is used to provide insight regarding performance characteristics and design limitations. The model is validated over a frequency range of 10–1000 Hz with hotwire anemometry measurements for both slot and orifice configurations for the jet. The model is useful as a design tool for electrodynamic ZNMF actuators. Nomenclature Amagnet = cross-sectional area of the permanent magnet, m 2 a = outer radius of the diaphragm, m aorif = axisymmetric orifice radius, m Bavg = average magnetic flux density acting on the coil placed in the magnetic assembly, T Bgap = magnetic flux density in the magnet gap predicted by magnetic circuit, T Br = remnant magnetic flux density of the permanent magnet, T b = inner radius of the compliant part of the diaphragm or the radius of the center boss, m CaC = acoustic compliance of the cavity, m 5 =N CaD = acoustic compliance of the diaphragm, m 5 =N CmD = mechanical compliance of the diaphragm, m=N c0 = speed of sound in air, m=s dC = diameter of the cavity, m dslot = diameter of the rectangular slot, m dT = overall diameter of the ZNMF actuator, m Ememb = Young’s modulus of the material of the compliant region of the diaphragm, Pa fN = undamped natural frequency of the diaphragm, Hz fr = steady-state resonant frequency of the diaphragm, Hz f1 = lower 3 dB cutoff frequency, Hz

Optimization and Test of 120 mm LARP Nb$_{3}$Sn Quadrupole Coils Using Magnetic Mirror Structure

The US-LARP collaboration is developing a new generation of large-aperture high-field quadrupoles based on Nb Sn superconductor for the LHC upgrades. The development and implementation of this new technology involves the fabrication and testing of series of model magnets, coils and other components with various design and processing features. New 120-mm HQ coils made of Rutherford cable, one with an interlayer resistive core, and both with optimized reaction processes, were fabricated and tested using a quadrupole mirror structure under operating conditions similar to those in a real magnet. The coils were instrumented with voltage taps and strain gauges to study the mechanical and quench performance. Quench antenna and temperature gauges were installed in the mirror structure to measure the coil temperature and locate quench origins. This paper presents details of the coil design and fabrication procedures, coil assembly and pre-stress in the quadrupole mirror structure, and coil test results.

Mechanical Behavior of the KSTAR Central Solenoid Coil Structure During Thermal Cycles

The central solenoid (CS) coil system of the KSTAR device consists of four pairs of coils with up-down symmetry and a set of support structure. The CS coil system should endure various loads including thermal and electromagnetic load during operation. One of the most important roles of support structure is to preserve the structural stability of coil system from vertical forces by applying the pre-compression on the coil stack. The main assembly procedure of the coil stack is as follows: 1) coil subassembly and stacking, 2) structure assembly, 3) preloading process by heating shells in the support structure, and 4) measurement on the final dimension. The special jigs and heating system for the preloading were designed to apply pre-compression on the coil stack during the assembly at room temperature. Moreover, a few tens of thermocouples and strain gauges were installed for measuring temperature and thermal expansion of preloading structures. Since the final assembly of the CS coil was successfully completed with about 7.3 MN of preloading in 2006, the CS coil system has been experienced four thermal cycles from 300 K to 5 K until 2011. This paper describes the main results of applying the pre-compression on the coil stack and mechanical behaviors of preloading structures during thermal cycles.

Magnetic Measurement of the Current Center Line of the Toroidal Field Coil of ITER at Room Temperature

Geometrical deformations and assembly errors in the ITER Toroidal Field (TF) coils will lead to magnetic field perturbations, which could degrade plasma confinement and eventually lead to disruption. Extensive computational studies of the influence of coil deformations and assembly errors on plasma behavior have given the basis for definition of the geometric tolerance of the Current Center Line (CCL) of the winding pack of the TF coil. This paper describes an analysis method to establish the feasibility to measure the magnetic CCL locus of the final winding pack (WP) with accuracy better than 1 mm. The proposed method is based on arrays of gradient coils accurately mounted with respect to the WP fiducial marks and datum surfaces. The magnetic measurements will be performed at defined locations around the WP perimeter to characterize accurately the CCL locus. The analysis emphases the robustness and sensitivity of the method versus the measurement location and the TF coil 3D geometrical deformation. The analysis and proposed measurement techniques will be described in detail.

Conduction Cooled High Temperature Superconducting Dipole Magnet for Accelerator Applications

A 3T proof-of-principle dipole magnet for accelerator applications, based on 2nd generation high temperature superconducting tape was designed, built, and tested by a consortium under the lead of Danfysik. The magnet was designed to have a straight, circular bore with a good field region of radius r = 25 mm, and a magnetic length of 250 mm. A total length of 2.5 km YBCO-based copper stabilized conductor supplied by SuperPower Inc., NY, USA, was isolated with 0.025 mm of epoxy and subsequently wound into 14 saddle coils and 4 racetrack coils with a cosine theta like configuration. The coils were impregnated with epoxy and mounted between a support of stainless steel and a collar made from aluminum. The cold mass consisting of the coil assembly and a laminated steel yoke is cooled by two cryocoolers from via copper bars to below 20 K. Current leads were made from the same batch of HTS tape. Cryogen-liquid free operation of an HTS accelerator magnet was demonstrated. The cold mass support design permits magnet orientation under arbitrary angles. Careful choice of materials in terms of magnetic, heat conducting and mechanical properties resulted in a robust and compact solution which opens up for accelerator applications in many fields, in particular where cryogenic liquid cooling is not an option.

Development of ITER sector assembly tools and mock-up

ITER sector assembly tools are customized tools for final integration of nine 40° sectors sub-assembled at assembly building and ex-vessel components. These tools include a central column, radial beams and their supports, assembly tools for poloidal field (PF) coils, and pre-compression ring (PCR) assembly tools and so on. The central column was designed to have sufficient strength to support nine 40° sectors and adjustment function of toroidal field coil (TFC). The PF assembly tools were designed also to support temporarily PF5 and 6 coils during sectors assembly duration, and to assembly PF coils to designated position with synchronized lifting and adjustment functions. Synchronized system applied to hydraulic cylinders of TF inner adjustment device and PF coil assembly tools is the key function to make highly precise assembly at final positioning. Hence, mock-ups were fabricated and tested to verify synchronized system of TF inner adjustment device and PF assembly tools. As results of tests, synchronized system operated by solenoid valves and linear sensors was verified to have high-resolution for final assembly of TFC and PF coils.

Single-core fluxgate gradiometer with simultaneous gradient and homogeneous feedback operation

A novel configuration of a single-core gradiometer, utilizing both homogeneous and gradient feedback operation, is presented. The fluxgate gradiometer comprises of a standard pick-up/feedback coil and an additional gradient pickup/feedback coil with two separate electronic blocks. The 40-mm-long gradient coil is concentric and coaxial with the homogeneous pickup/feedback coil: the gradient coil assembly was slipped over an already existing race-track fluxgate sensor. The gradient coil works as a pick-up coil and it also generates the compensating field which well approximates a first-order gradient field with zero spatial-mean value. Together with the compensating field from the homogeneous feedback coil, it is thus always possible to measure in two independent feedback loops the homogeneous and gradient field components. The 1/f gradient noise is 4 nT/m/√Hz @ 1 Hz, and it can be further improved by separating the gradient feedback and compensating coil.

The Short Model Coil (SMC) Dipole: An R&D Program Towards ${\rm Nb}_{3}{\rm Sn}$ Accelerator Magnets

The Short Model Coil (SMC) assembly has been designed, as test bench for short racetrack coils wound with cable. The mechanical structure comprises an iron yoke surrounded by a 20 mm thick aluminum alloy shell, and includes four loading pads that transmit the required pre-compression from the outer shell into the two coils. The outer shell is pre-tensioned with mechanical keys that are inserted with the help of pressurized bladders and two 30 mm diameter aluminum alloy rods provide the axial loading to the coil ends. The outer shell, the axial rods, and the coils are instrumented with strain gauges, which allow precise monitoring of the loading conditions during the assembly and at cryogenic temperature during the magnet test. Two SMC assemblies have been completed and cold tested in the frame of a European collaboration between CEA (FR), CERN and STFC (UK) and with the technical support from LBNL (US). This paper describes the main features of the SMC assembly, the experience from the dummy assemblies, the fabrication of the coils, and discusses the test results of the cold tests showing a peak field of 12.5 T at 1.9 K after training.

MR Continuously Variable Transmission Driven by SMA for Centrifugal Fan in Nuclear Power Plant

The running efficiency of centrifugal fan affects the economical efficiency of the ventilation system. In this paper, we proposed a continuously variable transmission system based on magnetorheological fluid and shape memory alloy for improving the operating efficiency of the centrifugal fan. The equation of transmission torque developed by magnetorheological fluid is derived to compute the torque transmission ability in the continuously variable transmission system. A shape memory alloy spring actuator is designed to control the electric current in coil assembly. The results indicate that the change of temperatures has a tremendous influence on the electric current in coil assembly, the transmission torque of the continuously variable transmission system changes rapidly according to the temperatures acting on shape memory alloy spring actuator, and the output angular velocity of the centrifugal fan can be adjusted continuously.

AUDIO SPEAKER HAVING A REMOVABLE VOICE COIL

An audio speaker (300) having a removable voice coil (320), which may be a part of a voice coil assembly (355). The voice coil may user-removable to facilitate replacement of a damaged voice coil or reconfiguration of a speaker system. Properly positioning the voice coil assembly may provide a solder-free electrical connection between the voice coil and leads that provide current to the voice coil. In some embodiments, the voice coil is user-removably attached to an inner circumferential surface of a diaphragm (310). In other embodiments, the voice coil is connected to the diaphragm (310), and the voice coil assembly (355) and the diaphragm (310) are both user removable attached to a frame (370).

Design and Implementation of Miniature 3-Axial Fiber Optic Rate Sensor

The key design and implementation methods of Miniature 3-axial Fiber Optic Rate Sensor are described in detail. Based on plenty of theoretical analysis and experimental validation, effective measures and key technology on optical components, fiber coil technics, assembly methods, control circuits and structure solidity are adopt and summarized. Finally, its main engineering performance is tested and listed detailedly. From experimental results and engineering practice, we can conclude that Miniature 3-axial Fiber Optic Rate Sensor has the performance of high reliability, radiation resistance, low air pressure resistance, temperature resistance and high reliability, and can be widely used in some special and professional fields. More importantly, it greatly promotes the development of fiber optic sensing and inertial technology application of China.

Design of a Large 5 T Superconducting Magnet for Polarized Target for JLAB Hall B 12 GeV Upgrade Clas12 Detector

Hall B at Jefferson Laboratory (JLAB) will need a 5 T, 78 cm bore polarized target magnet with a field uniformity of ΔB/B0 <; 10-4 in a useful cylinder of the dimensions 0.04 m long × 0.02 m in diameter. The large magnet is designed with a superconducting coil that provides the solenoid with nearly perfect self shielding in order to reduce the fringe field at nearby photo multiplier tubes (PMTs) to less than 3.5 mT. Because the solenoid is also very close to the Clas12 Torus, the nearly perfect shielding provided by the self shielded solenoid greatly reduces force, field, and torque interactions with the six-coil Torus magnet. The solenoid coil consists of 18 coil modules which are made of coils mounted in aluminum plate discs. Each coil module consists of dual double pancake coils with main coils and shield coil partitioned into separate winding cavities in the aluminum plate discs to distribute and reduce radial hoop load and radial coil forces. Each coil module is effectively an enclosed aluminum box and this serves to partition the axial load and thus reduces coil axial forces. Since overall coil forces within each coil module are reduced, this will greatly reduce the number coil training quenches. This is a very important consideration for this solenoid coil because the coil cooling is adiabatic, using in-direct conduction cooling by 4.5 K supercritical helium, which will provide only a relatively small temperature stability margin. Super critical helium is used as per JLAB specification. Detail design of the coil structure, coil assembly, cold mass, and cryogenic control will be presented. The magnet protection system shall be capable of the following features: (1) quench and fault detection, (2) fast discharge of the magnet, (3) limit fault voltages to safe values, (4) monitor interlock signals to prevent unsafe operation, and (5) provide control logic necessary for safe operation of the solenoid. The instrument systems shall be capable of the following features: (1) monitors and display temperatures within the solenoid magnet, (2) measure loads or stress on the magnet suspen sion, (3) monitor voltages within the solenoid magnet and charging bus, (4) monitor pressures and (5) use data logging system to save all sensor data. These systems will be described and a quench analysis presented.

Some Aspects of Winding Geometry Control for ITER Superconducting Coils Using Magnetic Measurements

A feasibility has been demonstrated for numerical reconstruction of geometrical displacement or deformations of the winding occurred in the manufacture and assembly of magnet coils using magnetic measurements, that is one of the principal issues for the quality control of the magnet. For validations of the proposed approach, test results of reconstruction of possible misalignments and deviations of the ITER coil are presented.

From Design to Development Phase of the ITER Correction Coils

The Correction Coils system (CC) within ITER, is intended to reduce the range of magnetic error fields created by assembly or geometrical imperfections of the other coils used to confine, heat, and shape the plasma. The proposed magnet system consists of three sets of 6 coils each, located at the top (TCC), side (SCC) and bottom (BCC) of the Tokamak device and uses a NbTi cable-in-conduit superconducting conductor (CICC) operating at 4.2 K. The ITER Organization (IO) and the Institute of Plasma Physics at the Chinese Academy of Sciences (ASIPP) are jointly preparing the definition of the technical specifications and the upcoming qualification program for the Correction Coils. The proposed design consists of a one in hand conductor winding without internal joint inserted in a structural casing which reacts the electromagnetic loads. The development of major items such as terminal joints, casing manufacture, and vacuum impregnation system, is an essential phase before the series production which will take place at the premises of the supplier. This paper discusses the key technologies on CC coils and future plans for short sample prototypes fabrication.

Development of a filled resin system for the TF coils of ITER

The final step in assembly of the ITER TF coils will be the insertion of the Winding Pack (WP) into the TF Coil Casing (TFCC). In order to facilitate mounting of the WP within the TFCC the design is made with clearance gaps of 7–10 mm to allow for manufacturing tolerances and WP adjustment during mounting. It will be essential to fill these gaps as the last step of the insertion operation. The fill process is a critical part of the operation; it completes the geometric location of the WP with respect to the casing and must provide for a uniform force transfer between the WP and casing. The properties and specification of the filler material are therefore driven by these two requirements. Two process options may be considered; direct fill by vacuum impregnation using a filled epoxy; or, pre-fill of the inter-space with dry particles (fibres or beads or powder) followed by vacuum impregnation with a low viscosity (unfilled) epoxy. This paper reports on experimental studies of both process options. The properties of a trifunctional epoxy resin system (TGPAP) filled with wollastonite, dolomite and milled glass fibres have been studied. Studies of flow and particle settling are reported. The same epoxy system has been used to impregnate samples pre-filled with dry particles, soda glass and alumina. Thermal contraction and mechanical strength measurements at 77 K are reported for both systems.

Embedded controlled low‐frequency AC to high‐frequency AC converter fed induction heater

PurposeThe purpose of this paper is to present, a novel boost‐active clamp bridge single stage high‐frequency zero voltage soft‐switching‐pulse width modulation (ZVS‐PWM) inverter, which converts the utility frequency AC power into high‐frequency AC power with an embedded controller. This single stage high‐frequency inverter is composed of a single‐phase diode bridge rectifier, a non‐smoothing filter, a boost‐active clamp bridge type ZVS‐PWM high‐frequency inverter, and an induction‐heated load with planar type litz wire working coil assembly. Also, the paper discusses how to extend the soft‐switching operation ranges and improve power conversion efficiency.Design/methodology/approachThe proposed converter is simulated and it is implemented using embedded controller.FindingsIt was found that the single stage high‐frequency induction heating (IH) inverter using boosted voltage function can eliminate the DC and low‐frequency components of the working coil current and reduce the power dissipation of the circuit components and switching devices.Originality/valueThe paper shows that the PWM HF inverter is preferred for IH, since it has reduced switching losses and switching stresses. The paper can be extended to PC‐based wireless control, which can be part of a distributed control system in major industrial heating systems.

Structure and Performance Analysis of Regenerative Electromagnetic Shock Absorber

This paper analyze d the structure and principle of a regenerative electromagnetic shock absorber in detail. The innovative shock absorber resembles linear generator in principle and can generate electric power through the relative reciprocating motion between coil assembly and permanent magnet assembly . A t the same time, the damping can remove discomfort caused by road roughness. The regenerated electric power can be recovered through battery. Analysis of magnetic flux density of the permanent magnet array of the innovative shock absorber was performed using ANSYS software based on the structure parameters given in the paper,then the performance parameters of the shock absorber was determined . Analysis and calculation results prove the viability of this shock absorber .

Ultrasound velocimetry of ferrofluid spin-up flow measurements using a spherical coil assembly to impose a uniform rotating magnetic field

Ferrofluid spin-up flow is studied within a sphere subjected to a uniform rotating magnetic field from two surrounding spherical coils carrying sinusoidally varying currents at right angles and 90° phase difference. Ultrasound velocimetry measurements in a full sphere of ferrofluid shows no measureable flow. There is significant bulk flow in a partially filled sphere (1–14 mm/s) of ferrofluid or a finite height cylinder of ferrofluid with no cover (1–4 mm/s) placed in the spherical coil apparatus. The flow is due to free surface effects and the non-uniform magnetic field associated with the shape demagnetizing effects. Flow is also observed in the fully filled ferrofluid sphere (1–20 mm/s) when the field is made non-uniform by adding a permanent magnet or a DC or AC excited small solenoidal coil. This confirms that a non-uniform magnetic field or a non-uniform distribution of magnetization due to a non-uniform magnetic field are causes of spin-up flow in ferrofluids with no free surface, while tangential magnetic surface stress contributes to flow in the presence of a free surface. Recent work has fitted velocity flow measurements of ferrofluid filled finite height cylinders with no free surface, subjected to uniform rotating magnetic fields, neglecting the container shape effects which cause non-uniform demagnetizing fields, and resulting in much larger non-physical effective values of spin viscosity η′∼10 −8−10 −12 N s than those obtained from theoretical spin diffusion analysis where η′≤10 −18 N s. COMSOL Multiphysics finite element computer simulations of spherical geometry in a uniform rotating magnetic field using non-physically large experimental fit values of spin viscosity η′∼10 −8−10 −12 N s with a zero spin-velocity boundary condition at the outer wall predicts measureable flow, while simulations setting spin viscosity to zero ( η′ =0) results in negligible flow, in agreement with the ultrasound velocimetry measurements. COMSOL simulations also confirm that a non-uniform rotating magnetic field or a uniform rotating magnetic field with a non-uniform distribution of magnetization due to an external magnet or a current carrying coil can drive a measureable flow in an infinitely long ferrofluid cylinder with zero spin viscosity ( η′ =0).