DC Electromagnet Research Articles

Optimization Design of DC Electromagnet Coil Considering the Power Consumption and Cost

Electromagnet coil is mainly composed of enameled wire which wound on the coil skeleton, and the function is to convert the electrical signal into a magnetic signal, which is a very important electric‐magnetic conversion element. When designing the electromagnet coil, usually only the total winding turns and winding inner diameter can be calculated, and the specific design parameters such as the diameter of copper wire, paint layer thickness, and winding turns of each layer can only be selected through experience, indicating that the design method should be improved. In addition, the unreasonable design parameters will seriously affect the power consumption and cost of coil, so it is highly necessary to improve the optimization design method. In order to solve the above problems, an optimization design method for DC electromagnet coil is proposed in this paper. This method simultaneously takes into account both power consumption and manufacturing cost, and can achieve the optimal matching of design parameters. In this paper, the structure of electromagnet coil is introduced, and the theoretical calculation model of resistance is improved first. Then, according to the expected requirements of electromagnet coil for steady current, the optimization design method is proposed and the optimal design parameters are obtained. Finally, the effectiveness of the proposed optimization design method is verified by the test platform of electromagnet coil. The results show that the electromagnet coil designed by the optimization design method fully meets the expected requirements. The relevant research results can provide reference for the optimization design of electromagnet coil, which has a certain engineering practical value. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Design and Development of Electromagnet Power Supply for Burst Mode Repetitive High Power Microwave Sources

Single frequency High-power microwave sources like Backward Wave Oscillator, Relativistic Magnetron etc., require a high magnetic field of about 1T to 4T for efficient operation. Single-shot HPM systems usually consist of pulsed magnetic systems. However, for repetitive HPM generation, a continuous magnetic field is required. To obtain a continuous high magnetic field in the required volume usually three solutions are worldwide preferred i.e., permanent magnet, DC electromagnet with cooling arrangements and superconductor-based magnetic coil. All these three systems are bulky, expensive and technologically demanding. In this paper, a novel power supply has been suggested that discharges a charged capacitor through a magnetic coil keeping the discharging current constant for a small period like hundreds of milliseconds to a second. An IGBT switch is used to discharge the capacitor1. The duty cycle of the IGBT switch is controlled using a current feedback signal from the hall sensor, thus keeping the current steady at a preset reference value. An experimental setup has been developed using a 300mF capacitor. A constant current up to 500A is achieved for 200mS. This system is scalable. For a longer duration of operation, more capacitor modules need to be added. Details of design, development and experimental results are presented in this paper.

Near-to-Zero Switching Synchronization Approach for DC Electromagnet Actuated Relays

This article puts forward an idea for dc electromagnetically (EM) actuated switching devices operation improvement by means of an electronic controller application. The idea is aimed at applying compensation for the movable armature inertia and the time required for coil (de)energization. Based on the results of the measurements of the tested contactors switching parameters, the most efficient (de)energizing conditions for “near–to–zero” synchronized switching (NZSS) method application were determined. The NZSS process realization approach operates on the principle of controlling the driving coil supply voltage delivery moment. By means of the same controller circuit, voltage-zero synchronized contacts making and current-zero synchronized contacts breaking operations were realized. The method was experimentally verified for various supply conditions and load parameters. Long-term tests confirm the suitability of the method for low-voltage (LV) EM actuated switching devices. The circuit was able to control various EM drives with no modification required for the structure in which it was used.

Exhaustive Optimization Method Applied on Electromagnetic Device

This paper presents the application of an exhaustive optimization method based on the design of experiments (DOE) and the finite element method (FEM), with the aim of improving the actuation force developed by a DC electromagnet. The optimization of this device has been the subject of several previous works, allowing comparisons between the optimization methods applied in terms of the obtained precision and the workload. According to previous studies, two geometric parameters (the angle ratio of the support tip and the coil shape ratio) are very influential on the force developed at the maximum air gap. Thus, the exhaustive optimization method took into account these two parameters for its maximization, having as constraints the maintenance of the global dimensions of the device (external radius, the height of carcass, height of the plunger with support) and of the cross-section of the winding. The optimization algorithm used the results of 2-D FEM numerical experiments carried out with the FEMM program in combination with the LUA language and is based on the response surface methodology (RSM) and analysis of variance (ANOVA). Second-order polynomial models of the objective function were calculated using full factorial designs with three levels per factor. After three iterations, a very good result was obtained, comparable to those obtained by other methods, but with a significant cost in terms of workload, the optimum obtained being a global one.

On the Possibility of In-Process Magnetic Detection of Flaws in Rails

A procedure has been developed to detect surface defects in the head and foot of a rail using a magnetic method involving thin-film magnetoresistive field sensors. The setup consists of a system for moving the rail in the longitudinal direction, a magnetizing solenoid, cartridges with field sensors for inspecting the rail head and foot, a DC electromagnet with attached pole pieces, and a “robotic” transverse movement unit with an additional cartridge for revealing long-sized defects (over the entire length of the rail). The electrical signals of the sensors are transmitted to an analog-to-digital converter and processed digitally. The possibility of detecting all surface defects stipulated by the regulatory and technical documentation of JSC Russian Railways is demonstrated.

The influence of the winding and the meridian section of the core on the magnetic moment of the electromagnet

The problem arising in the design of DC electromagnets, which is associated with the limitation of the application of the known methods for calculating the magnetic moment of an electromagnet, is described. The influence of the nonuniformity of the external magnetic field of the magnetizing coil on the magnetic moment of an electromagnet is analyzed to determine the limits of applicability of the assumption of uniformity of the external magnetic field. For this purpose, an iterative algorithm was used to numerically solve the integral equation for the surface density of fictitious magnetic charges on the surfaces of cylindrical elements of the core, considering the nonuniformity of the external magnetic field. It is established that the main cause of the discrepancy between the magnetic moment of the core of the electromagnet and the core, located in a uniform magnetic field, is the degree of nonuniformity of the external magnetic field of the coil, as well as the section of the magnetization curve, which corresponds the strength of the resulting magnetic field for the dominant part of the core. It is indicated that the region of application of the assumption of uniformity of the external magnetic field is limited by a relative core length and level of an external field. The influence of the shape of the meridian section of the core on the magnetic moment of the electromagnet is investigated. For core with washers, an iterative algorithm was used with a partitioning of the core medium into both cylindrical and ring elements to account for the additional edge effect due to the presence of washers. The results of the calculation have shown that their presence makes a significant contribution to the magnetic moment of the electromagnet, sometimes giving growth twice, and the level of contribution depends on the position and size of the washers, as well as on which section of the magnetization curve is the strength of the resulting magnetic field for most of the core in the absence of washers. It is shown that with increasing washer radius and a decrease of the distance from the washer to the ends the magnetic moment of the electromagnet increases, which is more pronounced for short cores and less pronounced for long cores .

Comparison of methods for calculating the magnetic moment of the cores of electromagnets of spacecraft control systems

The relevance of determining the magnetic moment of the core of a DC electromagnet of spacecraft control systems is shown. The review of methods for calculating the magnetic moment of a cylindrical core by demagnetizing factors and integral equations is made. Methods based on the use of demagnetizing factors are considered in more detail, their comparative analysis is made, and the field of application is investigated depending on the level of the external magnetic field and the relative length of the core. It has been established that the field of application of experimentally determined demagnetizing factors is limited by the range (60–100) of the relative length of the core and the upper limit of the level of an external magnetic field of strength 10000 A/m, and for other variants of relative lengths and levels, additional experiments are necessary. The determination of the demagnetizing factors under the assumption of the uniformity of magnetization is possible if the relative length of the core and the level of an external magnetic field exceed, respectively, the values of 100 and 40000 A/m. The use of demagnetizing factors under the assumption of constant magnetic permeability for cores of relative length not less than 60 with the level of an external magnetic field whose strength does not exceed 10000 A/m is not sufficiently substantiated, since its values may differ by an order of magnitude at different points of the core. The drawbacks of the method of demagnetization factors are noted and the necessity of using the method of integral equations is justified.

Control Unit for Electromagnet Current

The paper deals with the results of research and development of the electromagnet current control unit for the case when only two outputs without specifying the polarity of the source connection may be available from a circuit with a series of DC voltage sources and electromagnet winding. Theoretical results have been verified by modelling in Matlab-Simulink environment as well as by testing the starter of the contactor air switch.

Direct Off-Line Two-Switch Forward Converter with a Boost PFC Converter for Powering of DC Electromagnet Systems

In this paper a switch mode power supply design for electromagnet systems is presented. It is based on a boost converter with power factor correction and a two-switch forward converter. The powered electromagnetic systems in this research are part of various electrical contact apparatus such as electromagnetic contactors, relays, circuit breakers etc. The proposed schematic works in a wide input voltage range which solve the problem with the voltage sag occurring in the energy distribution system. The proposed solution ensures stable operation of the contact equipment and the relay circuits in their industrial application.

Estimation of power losses because of viscous friction in vibroisolation devices with electromagnetic stiffness compensators

In this research the method of the calculation of the power losses in DC electromagnet through eddy currents, which are analog of the viscous friction, is presented. The influence of these currents on the operation of the vibroisolator with the electromagnetic stiffness compensator is estimated. The losses of the power by eddy currents are less than 1 per cent of the electromagnet power itself and the compensator totally. The example of the calculation of the losses for eddy currents in steel conductor is also shown.

Eddy Current Impact Estimation in Designing Vibroisolator with 3D Electromagnetic Stiffness Compensator

In this research the method of the calculation of the power losses in DC electromagnet through eddy currents, which are analog of the viscous friction, is presented. The influence of these currents on the operation of the vibroisolator with the electromagnetic stiffness compensator is estimated. The losses of the power on eddy currents are less than 1 per cent of the electromagnet power itself and the compensator totally. The example of the calculation of the losses for eddy currents in steel conductor is also shown.

Minimizing the power consumption of a clapper-type dc electromagnet in intermittent operation

A technique for designing a clapper-type dc electromagnet with its power consumption being minimized is proposed. The technique is based on the experimentally obtained load characteristics and mathematical models of thermal characteristics of the winding that depend on the maximum temperature in its bulk. The optimality criterion for power consumption is determined, and an algorithm for searching for its best solution by two-phase scanning of the factor space is developed. The main dimensions of an optimized electromagnet are calculated as an example for different values of the initial parameters: the working gap, the counteracting force, the ratio of the maximum power supply voltage to the actuation voltage, and the power overload factor. Simple mathematical expressions for the determination of the main dimensions of an electromagnet are provided in order to reduce the time expenditure at the design stage. These expressions were obtained by generalizing the results of computational experiments using the methods of active experiment planning and the similarity theory. An algorithm for calculating these dimensions is outlined. The proposed technique was used successfully in the process of designing a new series of dc contactors for severe operating conditions.

Large DC Electromagnet for Semi-Industrial Thermomagnetic Processing of Nanocrystalline Ribbon

A large dc electromagnet with a 200 mm long air gap was designed, constructed, and tested. Analytical calculations provided the first approximation of required parameters. The design was refined with the aid of finite element modeling. Thermomagnetic processing required nominal flux density level to be 0.35 T. It was validated on a prototype that the average flux density in the air gap exceeded this value. The magnetizing coils were designed to be cooled by natural air convection. Despite a large size $({\sim}{\rm 1900}~{\rm kg})$ , the electromagnet was designed to consume less than 2.5 kW and could be energized from a single-phase mains socket.

Measuring cerebral hemodynamics with a modified magnetoencephalography system

Magnetoencephalography (MEG) systems are designed to noninvasively measure magnetic fields produced by neural electrical currents. This project examines the possibility of measuring hemodynamics with an MEG system that has been modified with dc electromagnets to measure magnetic susceptibility while maintaining the capability of measuring neural dynamics. A forward model is presented that simulates the interaction of an applied magnetic field with changes in magnetic susceptibility in the brain associated with hemodynamics. Model predictions are compared with an experiment where deionized water was pumped into an inverted flask under the MEG sensor array of superconducting quantum interference device (SQUID) gradiometers (R2 = 0.98, p < 0.001). The forward model was used to simulate the SQUID readouts from hemodynamics in the scalp and brain induced by performing the Valsalva maneuver. Experimental human subject recordings (N = 10) were made from the prefrontal region during Valsalva using concurrent measurement with the modified MEG system and near-infrared spectroscopy (NIRS). The NIRS deoxyhemoglobin signal was found to correlate significantly with the SQUID readouts (R2 = 0.84, p < 0.01). SQUID noise was found to increase with the applied field, which will need to be mitigated in future work. These results demonstrate the potential and technical challenges of measuring cerebral hemodynamics with a modified MEG system.

Development of a Compact Moving-Sample Magnetometer Using High-Tc Superconducting Quantum Interference Device

We developed a compact moving-sample magnetometer that uses a high-temperature superconductor–superconducting quantum interference device (high-Tc SQUID) to directly measure the flux coupled to a normal detection coil from a sample's magnetic moment in the presence of an external DC magnetic field. The moving-sample method is employed by inserting the sample between the poles of a DC electromagnet and vibrating the sample along the axis perpendicular to the external field axis using an actuator at a frequency of 2.693 Hz. First, the magnetic field of the sample is transferred by a first-order differential normal Cu coil to a SQUID for detection. Then, the SQUID output is fed to a lock-in amplifier for detection. The critical feature of the system design is the use of high-Tc SQUID, which enables the realization of a compact system. The basic characteristics of the developed system are presented, and the current system exhibited a detection limit of 1×10-7 emu.

Generalized statistical load characteristics of a forced double-winding armored DC electromagnet with a flat stop

Using the theory of similarity and planning of experiment in the FEMM software environment, the static load characteristics of a forced double-winding armored DC electromagnet with linear and nonlinear magnetic systems are described.

On the question of taking into account the main dimensions when selecting type of electromagnet according to value of constructive factor

Using the finite-element modeling of the magnetic field with the help of Finite Element Method Magnetics (FEMM) software, the influence of the ratios the electromagnet’s main dimensions on the values of constructive and efficiency factors has been stated. The possibility of taking into account the constructive parameters and the limits of their rational use more explicitly has been shown based on the example of calculating a suction DC electromagnet with a conical frustum that operates the air gap.

Investigation into magnetorheological abrasive honing (MRAH)

A scheme to finish external curved surfaces, by imparting rotation while the abrasive-mixed magnetorheological fluid (or abrasive-mixed MR fluid) is pushed up and down, is presented in this paper. Since the relative motions resemble those present in conventional honing, the proposed method is named as ‘Magnetorheological Abrasive Honing’ (MRAH). This paper outlines the design and development of magnetorheological abrasive honing setup. A DC electromagnet with cylindrical pole faces is used and measurement for magnetic flux density is done. Experiments are conducted with aluminum and austenitic stainless steel workpieces to understand the effect of magnetic field. Effect of initial roughness, workpiece rotation and process duration on finishing was investigated with ground austenitic stainless steel workpieces. It is observed that the improvement in finish is better for rougher surface and higher rotation speed of workpiece and a reduction in roughness is consistent with process duration.

Basic Characteristics of Rail Brake Systems Using Linear Motor Technology

An eddy-current rail brake system is effective in stabilizing the braking ability of trains because its braking force does not depend on adhesion between the wheel and the rail. However, the use of the existing type equipped with DC electromagnets causes the rail temperature to increase, bringing the possibility of rail bending. Because of this, it is impractical for use in Japan. Accordingly, we applied an AC electromagnet (the same as those used in linear induction motors) to the rail brake system to reduce rail temperature rise, and investigated its basic characteristics using a rotary-type test machine.

Electromagnetic launch assistance for space vehicles

Motivated by reducing the cost of launching space vehicles, the US National Aeronautics and Space Administration sponsored an industry/university research project to explore the application of electromagnetic forces. Here, the technical issues involved are examined, the initial achievements reported and further improvements suggested. If the initial launch phase of a space vehicle is horizontal instead of vertical, it is possible to use electromagnetic forces to supplement the rocket thrust, with consequent saving of rocket fuel. The short time of the horizontal launch phase (10–20 s) enables induction levitation to be used in combination with a compact form of a linear induction motor. The performance, dynamic characteristics and scaling laws of this system are examined. Induction levitation is simple and effective, but it has an oscillatory response to force or torque disturbances, and it is unsuitable for very large space vehicles. These problems can be overcome with magnetic suspension using controlled DC electromagnets. Although the energy required for electromagnetic launch assistance is small, the electrical power demand is very high, necessitating some form of local energy storage.