Magnetic Circuit Design Research Articles

A Simulation Magnetic Induction Tomography (MIT) for Agarwood using COMSOL Multiphysics

Magnetic induction tomography is an imaging technique used to image electromagnetic properties of an object by using the eddy current effect. (MIT) is a non-destructive method that greatly is used in the agriculture industry. This method provided an opportunity to improve the quality of agricultural products. MIT simulation was used for agarwood existence detection. This paper presented for the simulation system contains 7 channel coils receiver and a channel transmitter which is a sensing detector. This experiment aims to demonstrate the reaction of induced current density and magnetic field at 10 MHz frequency. Then, it also determines the optimal solenoid coil to be used for a better outcome for the magnetic induction system. The simulation result shows that coil diameter, coil length, and coil layer have a crucial role in the great performance of the induced current and magnetic field. The more coil turns, the greater the strength of the permanent magnetic field around the solenoid coil. The result of the simulation is important and needs to be considered to verify the effectiveness of the system for developing the magnetic induction circuit design.

Non-invasive local magnetic hysteresis characterization of a ferromagnetic laminated core

An alternative sensing solution is described to measure local magnetic hysteresis cycles through a laminated magnetic core. Due to the reduced space gap separating two successive laminations, it is impossible to interpose the usual oversize magnetic sensors (wound coil, Hall-effect sensor). In this study, the space issue has been solved by printing the needle probe method for the magnetic state monitoring and by using a micrometric Giant Magneto Resistance (GMR) for the magnetic excitation measurement. An instrumented magnetic lamination including the non-invasive monitoring solution has been built and moved successively to every lamination position of the whole laminated ferromagnetic core. A precise cartography of the hysteresis losses has been reconstructed from all these local measurements and the average values compared to the classic measurement methods obtained with a wound coil. The relative agreement between the experimental results observed opened doors to large improvement in the estimation of magnetic losses and in the design of magnetic circuits.

Magnetic circuit design and optimisation of magnetorheological mount with tapered channel under the flow mode

In order to relieve saturation of magnetic flux density in magnetic circuit, the flow mode magnetorheological mount with tapered channel is designed. The influence of geometrical parameters of the damping channel on magnetic flux density and pressure drop is analysed. The key parameters have strong nonlinear relationship with magnetic field strength and pressure drop. Then, the parametric modelling of magnetic circuit structure was carried out using ANSYS software as the analysis system. The mount optimisation analysis model was built based on ISIGHT software. The optimisation results showed that the designed magnetorheological mount improved the saturation point of magnetic flux density of the damping channel, and the resulting pressure drop had good controllability.

A Circular Tape Magnetic Circuit with an Elliptical Cross Section

A new class of magnetic circuits is presented, circular tape magnetic circuits with an elliptical cross section. They contain a rectangular part and two opposite half-circular parts. The parametric formula of the shaped cutting of the initial constant tape width is derived to obtain a sweep the winding of which on the mandrel allows making a circular magnetic circuit with an elliptical cross section of target dimensions. The tape is exposed to shape cutting and the magnetic circuit wound simultaneously in one device. The composite magnetic circuit design is considered that allows assembling magnetic circuits of varied size from standard ready-made components. The proposed class of magnetic circuits has a limit coil window filling coefficient equal to 1.

Development of vibration isolator using magnetorheological elastomer

Many vibration isolators, for example, passive vehicle mounting devices, have fixed rigidity. This article presents the development of an adjustable stiffness engine mount based on the magnetorheological elastomer (MRE) to reduce engine vibration. The development of the first MREs vibration isolator was to design the engine mounting, and then to simulate a magnetic circuit. The choice of housing material and the thickness of the MRE is considered to complement a sufficient and uniform magnetic field to change the stiffness. The innovative magnetic circuit design includes the type and size of the wire and the number of turns of the coil for optimal magnetic field. Finite Element Method Magnetics (FEMM) software was used to demonstrate the effectiveness of electromagnetic circuits in generating magnetic fields through MRE samples. Finally, influenced by the various current input in the coil, the performance of the MRE vibration isolator is investigated. The input electric current whose value increases is more useful to change the increased stiffness value of the MRE-based isolator system.

A new design of magnetic circuits in magnetorheological dampers for simple structure subjected to small stroke and low damping force

A magnetorheological (MR) damper is popularly applied for vibration control owing to its fast response and the easy controllability of the field-dependent damping force. However, most of the existing MR dampers developed so far possess design complexity and a high manufacturing cost due to complicated coil structures. To resolve these drawbacks of the existing MR dampers, a novel magnetic circuit positioned separately from the piston head of MR damper with a simple structure is proposed in this work. As a first step, a design configuration using the operating principle of the magnetic circuit is demonstrated, and subsequently, the magnetic analysis of MR damper is carried out through an analytical approach and the finite element method. In the magnetic analysis, the magnetic flux density is numerically calculated at various piston locations with different applied currents. After determining the principal design parameters of the proposed MR damper, experimental validation to demonstrate the concept of the new magnetic circuit is performed. The effect of the piston stroke length on the damping force is evaluated as a function of the current. In addition, it is discussed that the proposed MR damper can provide much higher control range of the damping force than conventional types of MR dampers in a low level of damping force.

Multi-objective optimization of magneto-rheological mount structure based on vehicle vibration control

Considering the influence of mount structure parameters on the quality of vehicle noise, vibration and harshness (NVH), a multi-objective optimization method of the magneto-rheological (MR) mount based on vehicle vibration control was proposed. A lumped parameter model was used to establish the relationship between the structure parameters of the MR mount and the NVH performance of the vehicle. Considering the influence of current on the magneto-rheological fluid viscosity and flow rate in damping channel, the dynamic characteristics of MR mount was obtained by the lumped parameter model. Then, a 10 degrees of freedom (DOF) vehicle model with MR mounting system was established. Finally, a co-simulation optimal platform was developed by the ISIGHT, MATLAB, and ANSYS software, and the non-dominated sorting genetic algorithm II was used to optimize the design of the mount magnetic circuit with the goal of improving the quality of vehicle NVH. The results showed that under the start/stop and the constant speed conditions, the root mean square values of vibration acceleration of the driver’s seat rail of the vehicle with the optimal design magneto-rheological mount decreases by 31.6% and 7.8%, respectively compared with the initial design mount, improved the ride comfort of the vehicle.

Verification of effect of secondary conductor bar on starting characteristics in line‐start type self‐excited wound‐field synchronous motor

This study clarifies experimentally the effect of the secondary conductor bar on line-start characteristics in a line-start type self-excited wound-field synchronous motor. This motor is based on a brushless wound-field synchronous motor having a rotor winding connected to a diode rectifier circuit. And it has a secondary conductor bar that is independently connected at a pitch of one pole, without end-ring. First, the operation principle of the proposed motor and its magnetic circuit design are described, and then the details of the prototype for principle verification are clarified. Next, when the combination of the connecting of the secondary conductor bar is changed, an experiment of line-starting characteristics and measured rotor field current is demonstrated. Consequently, it was clarified that the influence on the synchronous pull-in, speed ripple, and rotor field current.

Influence of liquid nitriding on the properties of the electric steel 10

Liquid nitriding (carbonitriding) effect on hardness, wear resistance and magnetic properties of electric steel grade 10 is reviewed here, as well as on the electric contact resistance. It was found that hot-rolled steel 10 loses its hardness as a result of annealing. Surface carbonitriding of specimens generates an improved layer of higher hardness, high wear resistance and increased electrical resistance. The specimens carbonitrided have contact electric resistance higher than that of hot-rolled specimens after descaling. The magnetic permeability of ‘grade 10’ steel does not practically change after annealing and carbonitriding, while the magnetic permeability corresponds to the magnetic field strength in a very typical way with typical parameters for carbon steels. Traditional methods of processing electrical steels, carried out in order to achieve such a complex effect, combine heterogeneous processes, such as electroplating, vacuum, plasma, high - temperature annealing, coating-are very expensive and difficult to implement. Carbonitration is more accessible for practical use and has a significantly lower cost. The results obtained can be used in the design of magnetic circuits for various electric devices.

Development of Brushless Claw Pole Electrical Excitation and Combined Permanent Magnet Hybrid Excitation Generator for Vehicles

Aiming at the problems of large excitation loss and low power generation efficiency of silicon rectifier generators and the unstable output voltage of permanent magnet (PM) generators, a hybrid excitation generator (HEG) with suspended brushless claw pole electrical excitation rotor (EER) and combined magnetic pole PM rotor is proposed in the present work. With only one fractional slot winding stator, the generator adopts PM field as the main magnetic field and electrical excitation field as the auxiliary magnetic field, which not only retains the advantages of high efficiency of PM generators but also effectively reduces excitation consumption. The main structure parameters and the design method were analyzed, and a simulation analysis of no-load magnetic field distribution and flux regulation ability was carried out using finite element software to verify the rationality of the hybrid excitation parallel magnetic circuit design. Moreover, the no-load, load, regulation, and voltage regulation characteristics of the designed generator were tested, and the results show that the designed generator has a wide range of voltage regulation, which can ensure stable output voltage under variable speed and load conditions.

Magnetic Circuit Design and Numerical Study of Diverging Stepped Magnetofluid Seal with Small Clearance

In order to obtain the maximum magnetic energy product in the sealing clearance of magnetofluid seal and improve its critical pressure, a diverging stepped magnetofluid seal with small clearance was designed based on the magnetic circuit design theory and the magnetofluid seal theory. Magnetic distribution and its theoretical critical pressure were calculated by the finite element method, which could prove the reliability of design method in the magnetic circuit. The paper studies the effects of axial clearance, radial clearance and pole tooth number on the pressure capabilities of diverging stepped magnetofluid seal in specific values, which were analyzed and compared in details. The results show that the magnetic flux leakage at the junction of the pole piece and the permanent magnet in the diverging stepped magnetofluid seal leads the theoretical critical pressure calculated by the magnetic circuit method to be lower than that calculated by the finite element method. Moreover, when the pole tooth number in the axial clearance is not less than the pole tooth number in the radial clearance, and the width of axial clearance is smaller than the height of radial clearance, the critical pressure of diverging stepped magnetofluid seal is better than that of the ordinary magnetofluid seal.

Improvement of Model Predictive Current Control Sensing Strategy for a Developed Small Flux-Switching Permanent Magnet Motor.

This paper presents an improved control system for a small flux-switching permanent magnet motor (FSPM) to enhance its performance and torque sensing. The analytical magnetic circuit design was used to determine the related motor parameters, such as the air gap flux density, permeance coefficient (Pc), torque, winding turns, pole number, width, length, magnet geometry, and the current density of FSPM. The electromagnetic analysis of this motor was performed by software (ANSYS Maxwell) to optimize the motor performance. In this study, the performance of FSPM was investigated by the uniform design experimentation (UDE). For the control system, the model predictive current control (MPCC) is currently recognized as a high-performance control strategy, due to its quick response and simple principle. This model contained the nonlinear part of the system, to improve the torque ripple of FSPM. A modified MPCC strategy was proposed to improve the distortion of the current waveform and decrease the computational burden. The new modified control architecture was mainly composed of three parts, such as the estimation of electromotive force (EMF), current prediction, and optimal vector selection/vector duration. When the reference voltage vector was obtained, the three-phase duties were easily determined by the principle of space vector modulation (SVM). The results show the different strategy methods between the newly proposed modified MPCC and traditional proportional integral (PI) controller. In the control of FSPM, a modified MPCC strategy was able to achieve a better performance response and decrease the computational burden. At a low speed of 350 rpm, the proposed modified MPCC can achieve a better dynamic response. The nonlinear problem of the startup speed was also effectively resolved. The torque sensing performance of the simulation and the experimental test value were compared. The torque sensing performance of the simulation and the actual test value were also examined. In this study, the optimization focused not only on the motor design and fabrication, but also on an improved motor control strategy and torque sensing, in order to achieve the integrity of the FSPM system.

Design of magnetic circuit and extraction system of ECR ion source for intense neutron tube

The magnetic circuit and extraction system were optimized to improve the utilization of neutral gas and neutron yield of a sealed intense neutron tube. An experimental system was established to study the relationship between microwave absorption efficiency and the magnetic field strength. The microwave absorption efficiency can reach 100% when the magnetic field intensity at the microwave window is 0.095 T. To further improve the distribution of ECR region, CST was used to simulate the internal magnetic field distribution of the ion source. The radial and axial magnetization results with the single and double magnetic rings were obtained by changing the position and spacing of the magnetic rings. There are three ECR regions and the location of ECR zones is suitable, when the distance between the center of the magnetic ring and the origin of the resonator is 12.5 mm and the distance between the centers of the two magnetic rings is 60 mm. A two-electrode slit extraction system was designed for uniform beam distribution on target. Compared with the original extraction system, the maximum current density is reduced by 82.5% and the target utilization area is increased by 38.54%, which will effectively reduce the thermal load of the target.

Mitigating Noncirculating Bearing Currents by a Correct Stator Magnetic Circuit and Winding Design

Different mechanisms by which bearing currents flow inside the electrical machine are well studied. In contrast, investigation and development of different techniques to mitigate these currents remain a field for improvement, and the final common solution to the problem has not been provided yet. In pursuit of addressing the problem, this article deals with noncirculating (or capacitive) bearing currents. The circuit mechanism of capacitive currents is explained in brief, and an approach for their mitigation is introduced. This article studies the influence of the stator winding and the slot geometry and presents different geometries to modify the motor to reduce the capacitive bearing currents. The effectiveness of the proposed mitigation technique is shown by finite-element-based modeling and verified by laboratory tests with different induction motor designs, where the winding and magnetic circuit geometries are varied. The technique can be used, in particular, for the mitigation of noncirculating currents, but it also offers potential for further research.

Features of heating technology at induction thermal processing with external electromagnetic field

According to the data of performed calculations and modeling of the hardening process, a design of inductors with magnetic cores for hardening long flat parts has been developed. At the design stage of this type of inductors, it was necessary to find out the degree of influence of the magnetic circuit design on the distribution of the temperature field during heating. To do this, we simulated electromagnetic and temperature fields to assess the concentration of the electromagnetic field at different heights of the “legs” of the inductor. As a result, a significant effect of the length of the “legs” of the magnetic circuit on the intensity of heating and the operability of the system as a whole was established. It is noted that insufficient height of the “leg” leads to a significant decrease in the field concentration, which leads to insufficient heating temperature and uneven distribution of heat zones in the heated part. In turn, an increase in the height of the “legs” leads to a narrowing of the heat release zone in the part compared to the total width of the coil and magnetic circuit. With a significant lengthening of the “legs”, the cooling circuit of the inductor will not be able to remove heat from the magnetic circuit obtained from the part, which will lead to the destruction of the magnetic circuit. The developed design of a two-turn single-circuit inductor and the general methodology made it possible to obtain a high-quality hardened layer with a depth of up to 3 mm with the formation of a martensitic structure of the required hardness on a planar-type flat part without significant energy loss. The part was machined by fixing it on a rigid base to compensate for the effect of temperature changes in linear dimensions. To obtain a uniform gap between the part and the inductor, a special pressure roller was used. The resulting structure of the hardened layer adequately meets the stated requirements for the part. The results of the research were used to develop a flat part of the “guide” type for lifting equipment (for example, a guide for the movement of the traction chain) and were introduced into production.

Coupled autotransformer and magnetic‐control soft‐start method for super‐large‐capacity high‐voltage motors

The large current generated by a direct start of the super-large-capacity high-voltage induction motor would have a huge impact on the power grid as well as the motor itself. Traditional soft starters have the shortcomings of discontinuous adjustment, voltage sags, sudden torque mutation, secondary current impact and high cost. To resolve this issue, the authors propose a novel coupled autotransformer and magnetic-control (CATMC) soft-start method. The structure of the new CATMC soft starter combines the functions of the autotransformer and magnetic control reactor via an innovative electric and magnetic circuit design. In this study, the authors analyse the magnetic circuit structure and working principles of the CATMC soft starter. Then, to validate its principle and performance, the authors conduct a simulation study using ANSYS software and design and test an 18 MW/10 kV CATMC soft starter prototype. The simulation results demonstrate that the CATMC soft starter effectively avoids secondary current impact and constrains the motor starting current to <2.5 times the rated current. The public connection point bus voltage also meets the voltage sag requirement of the IEEE standard and reduces the impact on the power grid.

A Magnetically Controlled Single-Stage AC–DC Converter

In this letter, a magnetically controlled single-stage ac-dc converter is proposed for low-power application which has the following features. First, single-stage operation is achieved by sharing switches between LLC resonant converter and totem-pole bridgeless power factor corrector (PFC) converter. Second, the power factor correction function is inherently achieved by designing the PFC converter to operate in discontinuous conduction mode. Third, the dc-link voltage is almost constant. Fourth, fixed switching frequency and duty cycle can be implemented for the switches, which simplifies the magnetic component and driver circuit design. Fifth, the LLC resonant converter is designed to operate at series resonant frequency, the highest efficiency operating point, so the converter can always achieve the maximum efficiency operation. Meanwhile, at this operating point, the converter output voltage is independent of the load so that it is functioning as a dc transformer; and finally, soft switching for all semiconductors is achieved. A 75-W experimental prototype is built to validate the proposed magnetically controlled single-stage ac-dc converter.

Design of Magnetic Circuit and Simulation of Magnetic Fluid Sealing with Three Magnetic Sources

In order to obtain the maximum magnetic energy product in the sealing gap of the magnetic fluid sealing structure to improve the pressure capability of the magnetic fluid sealing, based on the magnetic circuit design theory and the magnetic fluid sealing theory, a parallel connection with three magnetic sources is provided. The magnetic fluid seal structure is designed for the magnetic circuit. The magnetic field in the magnetic fluid seal structure is calculated by the finite element method, and the pressure capability of the magnetic fluid seal is calculated. The results are analyzed and discussed. The results show that the magnetic flux leakage at the junction of the pole piece and the permanent magnet and the axial length of the intermediate pole pieces are short, which results in a nonlinear relationship between the magnetic induction strength difference between the two pole pieces and the sealing gap between the two pole pieces. The magnetic circuit method is lower than the magnetic fluid seal pressure capability calculated by the finite element method of the magnetic field.

Magnetic Circuit Design and Magnetic Field Finite Element Analysis of Converging Stepped Magnetofluid Seal with Small Clearance

The stepped magnetofluid seal is an effective method for improving the pressure ability of ordinary magnetofluid seals (OMS) with large clearance. At present, the research on stepped magnetofluid seal with less than 0.4 mm small clearance has not been carried out yet. The equivalent magnetic circuit design of converging stepped magnetofluid seal (CSMS) with small clearance has been carried out and verified by magnetic field finite element method based on the CSMS theory and magnetic circuit theory. The effects of the width of the axial seal position, the height of the radial seal position, the number of the pole tooth in the axial seal position, and the number of the pole tooth in the radial seal position on the theoretical pressure ability of the CSMS are investigated by numerical simulation. The calculation results are analyzed and discussed. The results show that the magnetic flux leakage at the junction of the permanent magnet and pole piece causes the higher pressure ability of the CSMS structure designed by the equivalent magnetic circuit method than that calculated by the magnetic field finite element method. When the width of the axial seal position is greater than the height of the radial seal position and the number of pole teeth in the axial seal position is less than the number of pole teeth in the radial seal position, the CSMS has the best effect. Compared with OMS with small clearance, CSMS has greater advantages.

The Innovative Design of Deep In Situ Pressure Retained Coring Based on Magnetic Field Trigger Controller

Deep rock mass theory has not yet been completely established, which leads to a lack of theoretical guidance for deep resource development and poor continuity among engineering activities. The foundation of deep rock mechanics theory is to achieve the deep in situ rock fidelity coring (including the retaining of the pore pressure and temperature). To realize this, pressure‐retaining coring technology is required. A self‐triggered pressure‐retaining controller based on magnetic control is proposed in this paper. The pressure‐retaining controller realizes pressure‐retaining coring in any direction by triggering the closure of the valve cover by a magnetic force, forming a magnetic seal. Fifteen combined magnetic circuit design schemes are proposed. The magnetic flux density norm distribution and magnetic force evolution law of different schemes are then quantitatively analyzed by the finite element method. The results show that a complex magnetization combination can weaken the nonlinear negative correlation between the magnetic force and distance. The optimal design of the valve seat magnetic circuit is Scheme 9, with the valve seat consisting of four shape identical tile magnets. Among the schemes, for Scheme 9, the magnetic flux density norm of the valve cover is the most concentrated. The maximum magnetic flux density norm is in the middle, and the magnetic force at 35 mm from the valve cover to the valve seat is 2.915 N. Scheme 9 satisfies the minimum condition of the mechanical model and verifies the feasibility of magnetic field triggering. This research can be used to gain a better understanding of deep Earth properties and provides technology for the improved design of deep in situ pressure‐retaining coring devices.