Magnetic Saturation Phenomenon Research Articles

Impact factor on the measurement stability of Roche's coil

Compared with the traditional electromagnetic current sensor, Roche coil has advantage in no magnetic saturation phenomenon, simple structure, and has been widely used in current measurement. However, the measurement accuracy, bandwidth and sensitivity of Roche coils are still affected by a variety of factors, and the problem in ensuring the stability of the measurement system of Roche coils still remains to be a problem nowadays. This article is a review of how each factor affects the measurement stability of Rochester coils. In addition, Roche coils also have certain limitations, such as not being able to directly measure the size of the DC current for the principle of current mutual inductance , in order to make Roche coils to obtain a wider range of applications, this article mentions the zero-drift adjustment method, the method of AC superposition, the use of differential coils, and the method of the Hall effect sensor, which are of guiding significance for the future design of Roche coils capable of measuring DC currents.

Design and testing of a hybrid electromagnetic damping device for automotive applications

This study proposes a new design concept for combining a viscous fluid damper (VFD) with an eddy current damper (ECD). Three main concepts were thoroughly discussed: the magnetic system, the conductive material, and the housing. In particular, the excitation circuit and magnetic field were applied from the exterior of the main chamber of the VFD to minimize the intrusive risks introduced into the damper when trying to connect an internal magnetic system to an external power source.Experimental investigations on a test rig developed for this purpose were carried out in this work. The design aimed to generate eddy currents in an oscillating cylinder made of copper placed around an existing real-world car damper and secured to its moving rod. When exposed to an electromagnetic field, the newly designed system rapidly generated an extra level of damping in addition to the initial damping effect provided by the viscous mechanism. The obtained results showed that applying an electric current of only 1A increased the amplitude of the drag force by 12 % for an electrode with a thickness of 1.5 mm. A magnetic saturation phenomenon resisted any extra increase in the current. Making the metal conductor thicker is expected to increase the volume of the conductor in which the currents are flowing and, consequently, increase the damping effect.

Fuzzy Logic PI controller based Direct Torque control of a Self-Excited Induction Generator through a three-level Rectifier

The main goal of this work is to control the terminal voltage of a Self-excitation induction generator (SEIG) that supplies autonomous load and is driven by a variable speed wind turbine. More advanced strategies of control have been suggested and applied these through a two-level converter. However, in this paper, we propose to study a modified DTC approach which based on the use of three-level converter (NPC structure) and instead of the traditional PI controller, we use a PI fuzzy controller to reduce torque and flux ripples, the induction generator's stator flux and electromagnetic torque are controlled using voltage space vector selection. The proposed control strategy has to maintain constant DC bus voltage regardless of load or wind speed variations. Finally, it should be noted that this control accounts for the induction generator's magnetic saturation phenomenon.

A Simple DC-Offset Eliminating Method of the Series-Inductance Current for the DAB DC–DC Converter

Based on the phase-shift modulation, the dual-active-bridge (DAB) dc–dc converter always features the natural self-volt-second balance performance even during the transient process. Besides, different phase-shift ratios usually result in different initial series-inductance currents. Therefore, when the phase-shift ratio is suddenly changed for dealing with the change of required transferred power, a dc offset in the series-inductance current will emerge. Especially for the high-power condition, this dc offset lasts for a long time because of the high-current value but low damping conduction resistor. Then, the magnetic saturation phenomenon may emerge in the transformer, resulting in the potential failure of the converter system. To address this issue, a simple dc-offset eliminating method is proposed for the DAB dc–dc converter. Different from most of the existing methods, the proposed one is independent from the phase-shift modulation method. Therefore, the proposed dc-offset eliminating method can be easily embedded in different phase-shift modulation methods, such as single-phase-shift, double-phase-shift, and triple-phase-shift methods. Finally, the experimental results are provided to verify the effectiveness of the proposed dc-offset eliminating method for the DAB dc–dc converter.

Adaptive Feedback Linearization Control of SynRM Drives With On-Line Inductance Estimation

This article proposes an adaptive input-output Feedback Linearization Control ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FLC</i> ) techniques for Synchronous Reluctance Motor ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SynRM</i> ) drives, taking into consideration the iron losses. As a main original content, this work proposes a control law based on a new dynamic model of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SynRM</i> including iron losses as well as the on-line estimation of the static inductances. The on-line estimation of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SynRM</i> static inductances permits to inherently take into consideration the magnetic saturation phenomena occuring on both axes. As a major result, it permits a null stator current steady state tracking error even with a proportional derivative controller. The estimation law is obtained thanks to a Lyapunov-based analysis and thus the stability of the entire control system, including the estimation algorithm, is intrinsically guaranteed. The proposed adaptive <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FLC</i> technique, has been tested experimentally on a suitably developed test set-up, and compared experimentally with its non-adaptive versions in both tuned and detuned working conditions. Moreover, a sensitivity analysis of the performance of the adaptive <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FLC</i> to the variations of the stator resistance at low speed has been made. Finally, an analysis of the effects of the iron losses on the control performance and stability at high speed in the field weakening region at medium/high loads has been made.

Magnetohydrodynamic modeling and simulation of a vacuum arc plasma jet with a ring anode under different external magnetic fields

Supersonic plasma has been widely used. A vacuum arc ion source provides one possible method for generating supersonic plasma. An external magnetic field can effectively avoid the wall loss of the plasma in the ion source and improve the ion yield. In this work, a two-dimensional magnetohydrodynamic model is established, considering different components including ions and electrons. With the help of simulation, we explore the physical characteristics of the supersonic vacuum arc plasma formed from a copper disk cathode. The characteristics that we focus on include plasma composition, current density distribution, plasma velocity, and plasma temperature. These characteristics as well as the ion yield are compared when different magnetic fields generated by solenoids near the cathode are applied, as well as when the arc current is different. The results show that, in the absence of an external magnetic field, ions expand freely with the approximate axial velocity and average ion charge state. With the increase of external magnetic flux density, the wall loss of the plasma will decrease, and the axial velocity and average ion charge state will increase, but the magnetic saturation phenomenon exists. The simulation results are consistent with the experimental results.

A novel magnetorheological braking system with variable magnetic particle volume fractioncontrolled by utilizing shape memory alloy

To address the shortcomings of decreasing shear yield stress of magnetorheological fluid due to temperature increase, magnetic saturation phenomenon under the action of a strong magnetic field, and decreasing performance of magnetorheological brake due to magnetic particle settling, a braking system of variable particle volume fraction of magnetorheological fluid modulated by shape memory alloy spring is proposed, which solves the shortcomings of constant particle volume fraction magnetorheological brakes. The brake temperature rises and automatically increases the volume fraction of magnetorheological fluid, leading to increase in the braking torque and ensuring stable braking performance at high temperatures. The magnetorheological fluid particle settling stability is enhanced, and energy consumption at idle is reduced. Based on the shape memory effect of shape memory alloy, the relationship between the output displacement of shape memory alloy spring and temperature, squeezing pressure and volume fraction of magnetic particles is established. Based on the microscopic body-centered tetragonal structure of magnetorheological fluid, the relationship between the volume fraction of magnetic particles and the magnetic permeability of magnetorheological fluid was established. Based on the rheological characteristics of magnetorheological fluid, the relationship between the braking torque of magnetorheological fluid and the magnetic permeability and the volume fraction of magnetic particles is established; and the finite element method was applied to simulate and analyze it. The results show that the magnetic permeability increases with the increase of the volume fraction of magnetic particles and the braking torque increase with the increase of the volume fraction of magnetic particles during the evolution of the magnetorheological fluid microstructure from single chain to body-centered tetragonal structure. When the volume fraction of magnetic particles in the magnetorheological fluid increased from 15% to 45%, the magnetorheological brake torque increased to 10.1N·m, and the braking performance of the magnetorheological brake improved by 14.3%. The experimental and theoretical analyses provide a theoretical basis for the design and manufacture of magnetorheological fluid brakes with variable particle volume fractions.

An Integrated Elitist Approach to the Design of Axial Flux Permanent Magnet Synchronous Wind Generators (AFPMWG)

This paper addresses an integrated and developed approach to the design of an Axial Flux Permanent Magnet Wind Generator (AFPMWG). The proposed analytical method of design employs the size equations and precise inductance calculations simultaneously, as well as considering the mechanical constraints of the back-iron disc of the rotor. An Elitist Genetic Algorithm (EGA), such as a high capability optimization method, has been used to solve the equations and design of a wind generator with predefined rating power. The objectives of the coreless AFPMWG design process are minimizing the magnet consumption, maximizing machine efficiency, and achieving maximum sinusoidal induction voltage, considering the wind properties of the geographical area of utilization. The optimal calculation of the permanent magnet thickness is also taken into consideration in this work. The flux density distribution in all parts of the machine has been investigated for the magnetic saturation phenomenon. In this regard, special attention is paid to rotor back discs, which are made from nonlinear material with an optimum thickness. The inductance of the leakage flux of the coreless machine has been considered by parallel computation via the Finite Element Method (FEM) and analytical equations. Finally, three-dimensional and two-dimensional finite element analyses are used to validate the performance of the machine design according to the characteristics of Iran wind resources. The results show the high ability of the proposed approach in AFPMWG design and in considering the objectives and constraints carefully.

A Nonlinear SRM Controller Design for Torque Ripple Reduction with accounting for Magnetic Saturation

In this paper, a nonlinear backstepping controller design is proposed for torque ripple minimization in switched reluctance motor (SRM) drive systems, which ensures less acoustic noise and less vibration. The proposed controller is based on a model taking into account the stator coils magnetic saturation phenomenon. For the torque ripple optimization purpose, the excitation angles are adapted according to the instantaneous SRM torque and speed values. Therefore, a lookup table is built, proposing the excitation angles optimal values for different machine operation points. The proposed control strategy validation was carried out by simulation, using MATLAB-Simulink tools. More specifically, the Simpower system library was exploited, since it offers an SRM simulator, taking into account magnetic saturation. To highlight the supremacy of the proposed controller, its performances are compared with those of conventional linear (PI) regulator. The obtained results validate the proposed controller robustness and efficiency.

Dynamic Equivalent Magnetic Network Analysis of an Axial PM Bearingless Flywheel Machine

A nonlinear dynamic equivalent magnetic network model for an axial permanent magnet bearingless flywheel machine (APM-BFM) is proposed in this paper. The model focuses on analyzing the magnetic field changes at the air gap of the machine. According to the relative position of the stator and rotor, the magnetic circuit between the rotor and the suspension pole (the torque pole) is divided into 7 stages (8 stages), and dynamic equivalent magnetic network models are established. The local saturation coefficient is introduced to characterize the local magnetic saturation phenomenon of the rotor yoke during the rotation of the rotor. Using the proposed model and based on the obtained winding flux, the opposing electromotive forces and inductances of the suspension and torque windings of the APM-BFM are all analyzed and calculated. Finally, the validity of the proposed model is verified by finite element analysis (FEA).

Performance Analysis of a Self-excited Induction Generator Mathematical Dynamic Model with Magnetic Saturation, Cross Saturation Effect and Iron Losses

Construction of appropriate mathematical model of plant (object to be modeled) has especially important meaning for designing controller. A reliable and good control performance requires more detailed model. Nevertheless, the latter must be established from at least two viewpoints of preciseness and compactness. In this paper, the considered plant is a self-excited induction generator (SEIG). In order to improve the accuracy, we take into consideration in the SEIG modeling: magnetic saturation phenomenon, cross saturation effect and iron losses. To our best knowledge, this is the first time that the three mentioned phenomena have been integrated into the same and single SEIG model which is presented in an inherent mathematical form. As we will see in the results, the contribution of these three phenomena in the accuracy improvement is really significant. In addition, to achieve compactness of the proposed model, a simpler configuration is obtained for the electrical equivalent circuit associated to the studied model by using Thevenin transformation. The proposed model is built in MATLAB-SIMULINK environment and used to study and analyze the performance of a SEIG under various operating point conditions. The obtained results are compared to measurements and also to the values obtained from models without the three discussed phenomena.

A Proposed Approach for Separation between Short Circuit Fault, Magnetic Saturation Phenomenon and Supply Unbalance in Permanent Magnet Synchronous Motor

This paper proposes a new approach for discrimination between short circuit fault, magnetic saturation phenomenon and supply voltage unbalance in permanent magnet synchronous motor. This proposed approach is based on tracking the simultaneous position in the polar coordinates of the amplitude and phase angle of the voltage and current indicator FFT signals of the harmonics characterizing the three phenomena. The voltage indicator set using three supply voltages to check the status of the power source. In the same way, the current indicator defined using three line currents to discriminate between the short circuit fault and the magnetic saturation phenomenon. To highlight the effectiveness and the capability of this approach, a series of simulations are performed on signals obtained from a permanent magnet synchronous motor mathematical model. This model is based on a 2D-extension of the modified winding function approach.

Stator Inter-Turn Short-Circuit and Eccentricity Faults Detection in Permanents Magnets Synchronous Motors Using Line Current Spectrum Analysis

Stator inter-turn short-circuit and Eccentricity faults are among the most common types of faults encountered in permanent magnet synchronous motors. This paper proposes a new method for the diagnosis of these types of faults based on the motor current signature analysis. A mathematical model based on the modified winding function approach has been developed to model the healthy PMSM, considering the effect of the magnetic saturation phenomenon and in the presence of inter-turns short-circuits and eccentricity faults. In order to highlight the interest of the model employed and the efficiency of the spectral analysis technique of the stator current, a series of simulations are performed in the different operation modes (Healthy and faulty operation modes).

Magnetic Field Analysis of an Iron-Cored Tiered Type Permanent Magnet Spherical Motor Using Modified Dynamic Reluctance Mesh Method

This article develops a modified dynamic reluctance mesh (DRM) method that can be utilized to calculate and analyze the magnetic field of the iron-cored tiered-type permanent magnet spherical motor (T-PMSpM) effectively and efficiently, with the multi-degree-of-freedom (multi-DOF) movements taken into account. According to the structural characteristic of the iron-cored T-PMSpM, the tilting function part, including the tilting stator and rotor, is equivalent to a dynamic lumped-parameter magnetic network model. Besides, the magnetic saturation phenomenon of the iron materials is also considered. The DRM results of magnetic field distribution, flux linkage and back electromotive force (EMF) show a good agreement with the three-dimensional finite-element method results. For further verification, a prototype motor of the iron-cored T-PMSpM has been manufactured. The back EMF curves with different rotor tilting positions are measured by experiments and compared with the calculated results.

A two-phase simulation of convective heat transfer characteristics of water–Fe3O4 ferrofluid in a square channel under the effect of permanent magnet

In this numerical study, the hydrothermal characteristics of the water–Fe3O4 ferrofluid are investigated using the two-phase mixture model. The ferrofluid flows in a square channel and is under the effect of magnetic field produced by permanent magnet(s). A parametric study is performed to analyze the effect of different factors such as nanoparticles concentration and diameter, Reynolds number and magnet strength. It is observed that applying such magnetic field creates mixing in the flow and disturbance in the boundary layer development, leading to local enhancement in the convective heat transfer at regions close to the magnet position. Higher enhancement in heat transfer is observed when the ferrofluid with higher concentration and particle size is used. Using stronger magnets also improves the heat transfer rate, and the amount of enhancement is limited by the magnetic saturation phenomenon. Increasing the Reynolds number at a given magnet strength decreases the effectiveness of the applied magnetic field on the flow and heat transfer. To create more efficient mixing in the flow and disturbance in the boundary layer, four magnets at different positions are used. It is observed that the average convective heat transfer coefficient in case of using four magnets is about 40.79% and 58.19% higher than those of using no magnet with ferrofluid and pure water, respectively.

A Proposed Technique for Discrimination between Saturation Phenomenon and Short-Circuit Faults in Induction Motor

This paper proposes a new technique of discrimination between the two signatures related to the magnetic saturation phenomenon (MSP) and the inter-turn short-circuit (ITSC) fault in a three-phase induction motor (IM). This technique is based on the exploitation of the amplitude and the phase angle of a new harmonic characterizing both phenomenons obtained from the characteristics of the Hilbert transform. In addition, and in order to simplify the interpretation and analysis of the various modes of operation covered in this paper, a new graphical tool based on a triangular representation is proposed. This graphical representation depending on the position and the orientation of the triangle makes it possible to display in a simple and clear manner the existence of the ITSC fault and its discrimination with respect to the MSP phenomenon. To assess the performance of this new technique, some simulation works are performed on signals obtained from a mathematical model of the IM based on the calculation of the inductances by the modified winding function approach (MWFA).

Study on electromagnetic force of the new micro digital valve

Electromagnetic force is crucial to the performance of the micro digital valve. The bigger electromagnetic force is needed to improve the rapidity of the micro digital valve. In the light of the traditional electromagnetic structure, which layouts the spring at the middle of the electromagnet, a new electromagnetic structure which sets the spring at the top of the electromagnet is studied. The relevant parameters and material are researched in the paper. The cross-sectional area of air gas and the electromagnetic force have a positive correlation relationship. The bigger driving current and the more turn of coil can increase the electromagnetic force in a certain range. The magnetic field would get the saturated state while driving current get a bigger value. At the moment, the magnetic force would not increase. Influence of magnetic material and non-magnetic material for valve seat is tiny. Electromagnetic force has a little difference between the two installation shells in the process of demagnetization. The simulation model is accurate and reliable. Using the simulation model, the electromagnetic cross section area, the different shell materials and the magnetic saturation phenomenon are simulated.

A two-phase simulation for ferrofluid flow between two parallel plates under localized magnetic field by applying Lagrangian approach for nanoparticles

Abstract Hydrothermal characteristics of water–MnZnFe2O4 magnetic nanofluid between two parallel plates are evaluated under effect of localized magnetic field. The Eulerian–Lagrangian approach is employed considering the effects of Brownian, thermophoretic, magnetic, lift and drag forces. Convective heat transfer enhances by increasing each of the parameters of nanoparticle size, concentration and magnetic field strength. The rate of enhancement for convective heat transfer is lower at higher magnetic field strengths due to the magnetic saturation phenomenon. Concentration is non-uniform in transverse direction, and nanoparticles migrate to central regions. In the sections with positive magnetic field gradient, the magnetic force is exerted on the particles in the flow direction and consequently, velocity increases in the central regions while decreases near the walls. Conversely, in the sections where the magnetic field gradient is negative, the velocity decreases in the central regions while increases near the walls. This causes local changes in convective heat transfer. Moreover, the pressure increases along the channel in the sections with positive magnetic field gradient, whereas in the sections with negative magnetic field gradient, the pressure drops with a greater slope compared with the case without magnetic field. Additionally, the wall temperature decreases with increasing the magnetic field gradient.

Current Control of WRSM Considering Magnetic Saturation Phenomenon

This paper introduces the characteristics of a 120 kW class wound rotor synchronous motor (WRSM) considering the effects of magnetic saturation in electrical steel. The flux linkage due to the rotor windings and the $d$ -axis inductance of WRSM vary non-linearly because of the magnetic saturation. This affects the selection of a current combination for maximum torque per ampere (MTPA) control. The relation between the current combination for MTPA control and magnetic saturation is analyzed in this paper. Finding a current combination that satisfies the requirements is very difficult, because WRSM has complicated current combinations ( $i_{f}$ , $i_{d}$ , and $i_{q})$ . Therefore, an algorithm for the calculation of the optimal current is proposed using the Lagrange function, and the current map is presented. Finally, the validation of the selected current combination is performed through the comparison of the results of an experiment and the finite-element analysis.

Effects of structure parameters on the static electromagnetic characteristics of solenoid valve for an electronic unit pump

In the present paper, the effects of driving current and solenoid valve’s structure parameters (including iron-core’s length, magnetic pole’s cross-sectional area, coil turn, coil’s position, armature’s thickness, damping hole’s position, damping hole’s size, and width of working air–gap) on the static electromagnetic characteristics have been numerically investigated. From the results, it can be known that the electromagnetic energy conversion will be seriously influenced by driving current for its effects on magnetic field strength and magnetic saturation phenomenon, an excessive increase of current will weak electromagnetic energy conversion for the accelerating power losses. The capacity of electromagnetic energy conversion is also relative to each solenoid valve’s parameter albeit it is not very sensitive to each parameters. The generated electromagnetic force will be enhanced by rising iron-core’s length, equalizing the cross-sectional areas of major and vice poles, increasing coil turn within a moderate range, closing the coil’s position towards armature’s centre, enlarging armature’s thickness, pushing the damping holes’ positions away from armature’s centre, reducing the sizes of damping holes, and reducing the width of working air–gap; but such enhancements won’t be realized once the driving current is excessively higher.