Iron Core Coil Research Articles

Research on the Conduction-Cooled YBCO Magnet for an MW Class Induction Heating System

High-efficiency high-temperature superconducting (HTS) induction heating equipment has been regarded as a promising application for thermal processing of metal material, in which an HTS magnet generates a high magnetic field to form the background field in the iron core and the rotating billet is heated by eddy current to process temperature. Efficiency analysis for the traditional induction heating and new structures for the HTS induction heating are studied in this paper. A new type of superconducting induction heating magnet structure is proposed. Through the parallel connection of multiple magnetic circuits, it can make more effective use of the high magnetic field produced by superconducting magnets. The applicable range and application criterion of the new structure are also given. Calculation models for induction heating system electromagnetic field and billet region temperature field analysis are established. The megawatt (MW) class conduction-cooled Yttrium Barium Copper Oxide (YBCO) magnet system is designed. The magnet consists of an iron core and HTS coils wound with the spliced YBCO-coated conductors. The magnet system is cooled by two AL325 GM refrigerators and the operating temperature is 20 ~ 30 K. Furthermore, the prototype YBCO coils with the same thickness are fabricated and tested in the LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . Test result of the prototype magnet is presented.

Abstract A41: Biomechanics: A new therapeutic innovation deposit – From the proof of concept to the proof of efficacy

Abstract Malignant tissue can be normalized in vitro using mechanical signals. A biomechanical treatment has been applied to a tumor of human origin grafted subcutaneously in mice and demonstrated the normalizing effect of stress on tumor growth in vivo. Following this Proof of Concept, a feasibility study has been performed to build a prototype for a Proof of Efficacy: Application of a Constraint Field on human pancreatic cancer grafted in the pancreas of mice. Two devices are combined to generate the local constraint: First a generator of Gradient of Magnetic Field (GMF), second magnetizable iron nanoparticles located in the neovessels surrounding the tumor itself. Nanoparticles act as bioactuators transforming magnetic energy in mechanical energy. This feasibility study was performed on the GMF generator with two opposite permanent magnets. The pressure (Pa) created on the neovessels is: P = Fv.L.Ms,v.dB/dx L is the stroma thickness (m); Fv is the nanoparticle volume proportion of stroma; Ms,v is the magnetization of nanoparticles (A/m); dB/dx is the magnetic induction gradient in stroma thickness direction (T/m). Iron-core coils are the best means to obtain our goal: A magnetic pressure of about 100 to 500 Pa on the tumor surface. The tumor is a one-centimeter-diameter sphere located at the center of our measured zone, a tube with 3 cm square section. Three dimensional magnetic simulations with a finite element method show that a magnetic induction gradient of 50 T/m is achievable. This gradient can be maintained permanently, can vary with time, and can have a variable direction in the field of study. The other variables that increase pressure are: The proportion of iron particles (greater than 100 mg/ml), the thickness of stroma, and the magnetization of particles. The experimental laboratory environment in which the anesthetized rodents are studied must permit heat dissipation to obtain reproducible results with no influence of temperature. The power losses do not exceed 600 watts, so the use of air-cooling is adequate. The magnetic induction gradients are strong, but obtainable at the tumor-stroma interface. The progression to a whole human prototype will necessarily require supra-conductor coils. We will present the data on changes in in vivo human tumor size and configuration with the application of external quantifiable constraint field in the experimental mouse. Citation Format: Remy Brossel. Biomechanics: A new therapeutic innovation deposit – From the proof of concept to the proof of efficacy. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr A41.

Construction and evaluation of rodent-specific TMS coils

Rodent models of transcranial magnetic stimulation (TMS) are crucial for understanding the cellular and molecular mechanisms underlying TMS induced plasticity in humans. However commercial coils used to stimulate rodents lack the spatial resolution used clinically. Here we describe two novel TMS coils designed for focal stimulation in rodents. Two circular coils (8 mm outer diameter) were constructed with either an air or pure iron core. Peak magnetic field strength for the air and iron-cores were 90mT and 120mT respectively, with the iron-core coil exhibiting less focality. Coil temperature and magnetic field stability for the two coils undergoing repetitive TMS (rTMS), were similar at1Hz but varied at 10Hz. To test the biological relevance of the coils, we applied rTMS in rodents to examine changes in cortical excitability (motor evoked potentials) and molecular markers (western blot and ELISA) implicated in TMS neuromodulation. Preliminary results suggest 5Hz rTMS delivered with the iron-core coil suppresses motor evoked potential amplitudes in anaesthetised rats. Analysis of molecular data is ongoing. Our results suggest the coils are suitable for the use in rodents and provide the opportunity to investigate the mechanisms underlying TMS in an experimental setting.

An accurate online calibration system based on combined clamp-shape coil for high voltage electronic current transformers

Electronic transformers are widely used in power systems because of their wide bandwidth and good transient performance. However, as an emerging technology, the failure rate of electronic transformers is higher than that of traditional transformers. As a result, the calibration period needs to be shortened. Traditional calibration methods require the power of transmission line be cut off, which results in complicated operation and power off loss. This paper proposes an online calibration system which can calibrate electronic current transformers without power off. In this work, the high accuracy standard current transformer and online operation method are the key techniques. Based on the clamp-shape iron-core coil and clamp-shape air-core coil, a combined clamp-shape coil is designed as the standard current transformer. By analyzing the output characteristics of the two coils, the combined clamp-shape coil can achieve verification of the accuracy. So the accuracy of the online calibration system can be guaranteed. Moreover, by employing the earth potential working method and using two insulating rods to connect the combined clamp-shape coil to the high voltage bus, the operation becomes simple and safe. Tests in China National Center for High Voltage Measurement and field experiments show that the proposed system has a high accuracy of up to 0.05 class.

Development and experimental research on circumferential impulse microturbine power generation system

Circumferential impulse microturbine is a key component of the micro-electro-mechanical system and provides power to the latter. An innovative concept of microturbine power generation system was presented, and prototype improved circumferential impulse microturbine power generation systems were developed, and their output performances were tested. It is validated that the system can operate at a high speed in a dynamic equilibrium state using rolling bearings, and it is found that the output power and rotational speed of a six-blade turbine hollow-cup coil structure is higher than the output power and rotational speed of a six-blade turbine iron-core coil structure. The maximum output power of the eight-blade turbine hollow-cup coil power generation system is 1.1 W, and the maximum turbine rotational speed is 55,000 r/min. The maximum output power of the eight-blade turbine hollow-cup coil system increases up to 25% when compared to the six-blade turbine hollow-cup coil system and increases up to 83% when compared to the six-blade turbine iron-core coil system.

Electromechanical modeling of a pinion-engaging mechanism for starter motors

The goal of this paper is to present an inductance measurement method, and an electromechanical model of the pinion-engaging mechanism for the starter motors. The pinionengaging mechanism is the system of components (solenoid switch, pinion-engaging lever, and overrunning clutch with drive pinion) that engages the drive pinion of the starter motor with the ring gear of the internal combustion engine. The actuator of the pinion-engaging mechanism consists of two concentric iron core coils. The coils are excited by relatively high currents. The electromechanical model of the pinion-engaging mechanism requires inductance of the solenoid and its derivative depending on the position of the iron core.

3D transient temperature field analysis of the stator of a hydro-generator under the sudden short-circuit condition

In this study, Finite Element Method (FEM) is applied to calculate the 3D transient temperature field of the stator of a hydro-generator, SF125-96/15600, under the sudden short-circuit condition. 3D transient equation of the heat conduction and its equivalent functional equations are firstly presented. Then the sudden short current and transient heat generation of the stator are analysed and calculated. Moreover, all the parameters for the simulation such as the heat conductivity coefficients of the iron core and stator coils, heat convection coefficients of each surface as well as iron and copper losses are deduced. These parameters are verified to be reasonable by comparing the simulated temperature results with the measured in the stable state. Finally, the 3D transient stator temperature field of the hydro-generator under the sudden short-circuit condition is simulated. The variation of the temperature field and temperature rise of the key components is also predicted, on which online thermal monitoring of the stator and optimum design can be carried out.

Study on a New Program of Passive Fiber Optic Current Sensor

With the raise of the grade of voltage and current in the transmission line, the traditional current transformer based on electromagnetism theory can no longer satisfy the requirement of actual measurement in recent years. Therefore a new method of fiber optic current sensor is presented in this paper. Taking the iron-core coil with air gap as current transformer in high-voltage side, the system loads the weak current signal created by mutual inductance into thin film resistor. And the strength of electric current can be known indirectly by measuring the temperature of thin film resistor. On the basis of its structure and testing conditions, supporting with finite element software ANSYS, a three dimensions model about thin film resistor is developed and thermal analysis on it is done. The temperature characteristics of the device obtained by ANSYS can provide a basis for the analysis on the current transformer.

A Nonlinear Compensation Approach for the Iron-Core Coils Based Electronic Current Transformers

Iron-Core coils based electronic current transformer is often used with electrical measuring instrumnts and meters. However, the iron-core coils used as the primary current sensor have nonlinear behavior, and its magnetizing current can be considered as the main error source. Therefore, a nonlinear compensation approach for the iron-core coils based electronic current transformers is proposed in this paper. The approach depends on a linear hardware circuit and a nonlinear numeric control law. Theoretical analysis and experimental results have verified the correctness of the proposed method.

The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HTS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HTS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets.

Research on stator temperature field of a hydro-generator with skin effect

Finite-element method is applied to calculate the stable stator three-dimensional (3D) temperature field of a hydro-generator SF125-96/15600. First, 3D controlling equation of heat conduction and its equivalent functional equation are presented. Secondly, all the parameters for simulation such as heat conductivity coefficients of iron core and stator coils, heat convection coefficients of each surface, are calculated. Thirdly, iron and copper losses are deduced by electromagnetic analysis. Then, the stator temperature field with and without skin effect are calculated. Comparing the two kinds of simulation results with that of measured, it is verified that the simulation is effective, and that the temperature field of slot under skin effect is more uneven than that of without the effect. So, more accurate temperature distribution of the key component of hydro-generator can be got on which online stator thermal monitoring and optimum design can be carried out.

VERTICAL NONCONTACT POSITIONING H∞ ROBUST CONTROL FOR MAGNETICALLY LEVITATED SURFACE MOTOR

To fulfill the stringent requirement,super-precision positioning and ultra cleanness,a surface motor with the integrated chip fabrication equipment is constructed by using permanent magnets and electromagnet coils as primary actuating components. It consists of stator and mover,and the mover is isolated from the stator by the magnetic bearing. The magnetic bearing in the stator is composed of eight air core electromagnet coils,the propulsion in the stator is composed of iron core and electromagnetic coils,and the mover is composed of NdFeB permanent magnets and levitated stage. Based on Lorentz law,some parameters,including permanent magnets dimensions,currents and levitation height,which may affect the stability,are analyzed and optimized. To improve the positioning accuracy in the vertical direction of the magnetic levitation surface motor,a robust controller is proposed using H∞ mixed sensitivity control theory. The simulation results show that by choosing appropriate weight functions,the controller can ensure the robustness of the closed loop system under the presence of uncertainties,and the H∞ robust controller is excellent for reducing steady error and increasing response speed.

Modelling and identification of a non-linear saturated magnetic circuit: Theoretical study and experimental results

This paper deals with the phenomenon of magnetic saturation in electrical machines. Taking magnetic saturation into account leads to non-linear models which need to develop parameter estimation techniques well adapted. At first, the study concerns an elementary model of saturated iron core coils and the physical parameter estimation of this non-linear model, thanks to a Non-linear Programming algorithm.

Calculation of extra copper losses with imposed current magnetodynamic formulations

To solve a magnetodynamics problem, two potential formulations can be used. In the case of the A-psi formulation, the voltage at the terminals of a conductor is naturally imposed, which is not the case for the current flowing through the conductor. On the contrary, for the T-Omega formulation, the current can be naturally prescribed, but not the voltage. In order to impose the complementary electric quantity in both formulations, a physics-based approach using a power balance is proposed. Both magnetodynamic formulations are presented by considering a domain made up of multiple conductors. These formulations are used to study the copper losses induced by the franging of the magnetic flux around a small air gap of an iron core coil. Theoretical results are compared with experimental results

Consideration of the coupling of the magnetic and electric equations with Finite Integration Technique (FIT)

In this paper, the Finite Integration Technique and an approach to solve simultaneously the magnetic and electric circuit equations is presented in magnetostatic case. The developments of the FIT will be compared with those used for the Finite Element Method. As example of application an iron core coil is studied and the results of both approaches are compared.

Field pulse magnetization of power PMSM rotors

This paper proposes a power pulse magnetizing system (magnetizer) dedicated to magnetize, at once, the entire rotor with surface-mounted rare-earth permanent magnets (PMs) of a high-speed, medium-power, permanent magnet synchronous machine (PMSM). The main component of the realized power magnetizer consists of a cylindrical iron core coil (magnetizer inductor), similar to a two-salient-poles-stator type of dc electrical machine, with an inner diameter corresponding to the internal diameter of the PMSM stator. A power pulse supply provides a field pulse into the magnetizing inductor.

Magnetic Field Analysis of Iron-Core Reactor Coils by the Finite-Volume Method

An accurate evaluation of the magnetic field of the iron-core reactor coils by the finite-volume method (FVM) is presented. The linear and quadratic interpolation scheme of FVM is developed. The numerical results are compared with those obtained by the finite-element method. Good agreement is obtained. The main advantage of the approach proposed is that the formation of coefficient matrix is very straightforward without needing the complicated mathematical derivation.

Po-topic IV-14: Imaging & localizing device using the barkhausen effect

We have been investigating the use of amorphous magnetic materials as locator tags for medical applications. Heinrich Barkhausen discovered in 1919 that a slow, smooth increase of magnetic field applied to a piece of ferromagnetic material, such as iron, causes the material to become magnetized not continuously, but in small steps. A large Barkhausen effect (large step change) was observed in 1931 because of domain reversal at a rapid velocity along the wire. In the late 1980s, an even larger Barkhausen effect was produced in amorphous wires giving rise to an even sharper magnetic pulse because of domain or flux reversal in the core of the wire. In an AC magnetic field, the reversal of the domains emits large, sharp magnetic pulses of the opposite sign. We are taking advantage of this pulsed response to tag and image the location and orientation of implanted devices. Several factors affect the feasibility of imaging and reconstruction of embedded tags. These include the strength of the detected signals; the ability to reconstruct locations and orientations of the tags; and signal sensitivity to tissue composition, inhomogeneities, and the presence of neighboring metals. We have obtained voltage signals from wires of several diameters with an iron-core pickup coil along a distance from the center of a wire with the coil as a function of angle for a 60–80 Hz driving field. At a distance of about 8 cm., we have obtained a strong signal of typically 2V (depending on length), more than 50 times the background noise (about 20 mV). At 30 cm separation, we detected a signal of 0.5 V, 25:1 above background noise. When the wire direction is mis-oriented relative to the driving AC magnetic field, the amplitude and phase of the resultant output signal changes. This is because only the portion of the magnetic field that is parallel to the wire axis contributes to the Barkhausen effect for that wire. By using multiple positions of the coil, we have been able to determine the changes of these two parameters for a more accurate localization. We have also determined that intervening tissues have little effect on the signals, as was expected theoretically. Our preliminary results indicate that in vivo 3D reconstruction is feasible.

Models for capacitive effects in iron core transformers

The paper presents an efficient modeling technique for iron core coils and transformers based on a separation of the nonlinear inductive effects from the linear capacitive effects. The magnetic field is numerically analyzed neglecting the displacement currents. The distributed capacitive effects in the insulation between coils are concentrated in an Extended II scheme, an infinite circuit which is optimally reduced to a finite one. The separately extracted models are integrated in a common discrete (lumped) system. This global model obtained by postprocessing the numerical field solution was used to study the transmission of atmospheric lightning overvoltages to the secondary windings of power transformers.

Determination and utilization of the source field in 3D magnetostatic problems

In this paper we study different approaches to introduce the source terms due to the inductors crossed by a uniform current density J/sub 0/ in 3D FEM. Two equivalent methods are developed to decompose the current density J in the facet element space with divergence free close to J/sub 0/. This decomposition is used in the a-formulation without gauge condition. Moreover, from the flux facet the source field H/sub s/ can be calculated in the edge element space and introduced into the /spl phi/-formulation. As examples of applications we have studied a coil with a complex geometry and a iron core coil.