Electromagnetic Attractive Force Research Articles

Magnetic focusing sensor and its characterizations of defect non-destructive testing for ferromagnetic steel plate

The fast development in precision manufacturing and product quality inspection of ferromagnetic material desperately demands that the defect determining the performance, service life and reliability of the mechanical part should be accurately sensed, detected and evaluated. However, conventional defect detection methods and related magnetic induction sensors are usually characterized with low accuracy in small defect detection, which makes the non-destructive testing (NDT) for ferromagnetic material full of challenges. Thus, a new magnetic focusing sensor is proposed and designed for the precision defect detection of ferromagnetic steel plate here. First, the theoretical principle analysis of the magnetic focusing sensor is introduced, and the preliminary finite element modeling (FEM) is conducted to demonstrate the feasibility of the magnetic focusing sensor in tiny defect inspection. Then, both the static and coupling dynamic characterizations of the magnetic focusing sensor are investigated using the FEM method. The optimal structural parameters of the magnetic focusing (MF) sensor in static conditions are summarized. Furthermore, the effects of the dynamic movement of the MF sensor on the multi-physical fields of the magnetization field, electric field, electromagnetic attraction force field and thermal field are all revealed. Finally, experiments regarding the performance evaluation and comparison between the MF sensor and other two magnetic flux leakage (MFL) sensors are conducted, and the prominent capabilities of accurate and precise defect detection for the MF sensor is demonstrated through the defect detection with different sizes. The effectiveness and feasibility of the MF sensor in detecting tiny defects on ferromagnetic object, as well as its great potential for practical application is therefore validated. Additionally, the main conclusions, advantages of the MF sensor are summarized and the future work is discussed.

Improved SEM Current Ringing Suppressor for Maglev Trains

In electromagnetic suspension (EMS) systems, the air gap between the suspension electromagnet (SEM) and steel track is adjusted by changing the electromagnetic attraction force, which is accomplished by controlling the maglev chopper (MC). When switching the power electronic devices of the MC, SEM current ringing tends to occur, which is harmful to the whole EMS system. A conventional current ringing suppressor (CRS) deteriorates the SEM port voltage ringing, which may accelerate the aging process of SEM insulation or even directly result in a breakdown fault. Herein, to explore the generation mechanism of SEM current ringing, a third-order equivalent circuit model of the suspension electromagnet-maglev chopper (SEM-MC) system is established by using the field-circuit coupling analysis technique. A series of simulations and experiments have been undertaken to verify the validity of the built circuit model, and the deviation between the simulation and experimental results is acceptable. As the influencing factors of SEM current ringing are analyzed based on this third-order equivalent circuit model, an improved CRS, i.e., hybrid inductor-resistor CRS, is proposed to avoid deteriorating the SEM port voltage ringing and protect the SEM insulation. Finally, the feasibility of the proposed hybrid inductor-resistor CRS is verified by corresponding experiments.

Displacement amplification enhances rapid actuation of electromagnetic actuators: Drive with load of spring–mass–damper system

Displacement amplification affects the response time of actuators using electromagnetic attractive force. Although this force is widely used for actuation, it exhibits a tradeoff between thrust and stroke, because thrust depends on the gap between the electromagnet and armature, and increasing the gap (stroke) drastically degrades thrust. Displacement amplification has been proposed for actuators to mitigate this tradeoff by magnifying the gap motion to efficiently use large forces in small gaps. Although such an actuator is applicable to submillimeter stroke and fast motions, dynamic characteristics have not been studied enough for designing in practical usages. This paper reveals the effect of displacement amplification on the actuation time through both a simple dynamic model for basic theoretical discussion and a simulation including damping factor to gain a more practical perspective. We also propose a test bench to verify the analyses and compare experimental and simulation results. The experiments confirm shorter actuation time and thus improved performance by combining electromagnetic attractive force and displacement amplification with spring–mass–damper as load. In addition, the experimental and simulation results show that only characteristics of the magnetic circuit should be considered for deciding the amplification ratio in designing DAEAs.

Experiment, Optimization, and Design of Electromagnetic Track Brake for High-Speed Railways System

To enhance braking force and control convenience of high-speed railway systems, this paper proposes a new electromagnetic track brake, and the corresponding design, optimization, and experimental test are implemented. The proposed track brake is longitudinal-axis magnetic circuits excited by multiple coils electromagnets, and the pole shoes are extending outward. A preliminary design of an electromagnetic track brake is developed, including iron core height, iron core width, iron core gap, excitation ampere-turn, coil arrangement form, coil thickness, and preliminary height of single-layer coil. The electromagnet number and pole shoe gap are optimized through three-dimensional electromagnetic simulation comparisons. The final design of the electromagnetic track brake is determined, including iron core length, copper wire diameter, coil turn, and final height of single-layer coil. Experimental verification of electromagnetic attractive force is performed through prototype tests, and the newly developed electromagnetic track brake can enhance electromagnetic braking deceleration by 39%.

Optimization of Braking Force for Electromagnetic Track Brake Using Uniform Design

Electromagnetic track brake is increasingly applied to improve emergency braking force together with the main wheel-rail brake system, while larger electromagnetic braking force is demanded. The bottom of pole shoe is designed as the same curved surface like track top in order to achieve a good contact between pole shoe and track and the pole shoe chamfering is also designed to improve electromagnetic attractive force. Three main variables that decide the electromagnetic attractive force are selected in the paper: pole shoe contact width, protection block length and pole shoe length. The reliability of electromagnetic simulation is verified through prototype test and then the electromagnetic attractive force in this study is achieved by electromagnetic simulation. First, the effects of the three variables on electromagnetic attractive force are investigated singly. Then, a uniform design method is employed in this study to further optimize electromagnetic attractive force by researching the interactional effects of the three variables. A regression model is established with pole shoe contact width, protection block length and pole shoe length as the independent variables, and electromagnetic attractive force as the dependent variable. Depending on the regression model, the optimum conditions of the three variables are achieved. In addition, finite element simulation of electromagnetic track brake is developed to investigate electromagnetic attractive force and magnetic field distribution by Ansoft Maxwell. Compared to the existing electromagnetic track brake, the electromagnetic braking force and electromagnetic braking deceleration of the optimized electromagnetic track brake are improved by 6.3% under the optimum conditions, which can greatly improve train safety in emergency. The proposed reinforcement optimizations have two outstanding characteristics. The first is keeping the space usage of electromagnetic track brake unaltered, and the other is its simplicity to conduct.

Experimental investigations of wave-DSRR interactions in liquid-phase media

In this paper, the mechanical displacement and the resulting resonance shift of a basic double split ring resonator (DSRR) which is placed in different low-loss liquid-phase environments are experimentally demonstrated. Such resulting dynamic process is due to the wave-DSRR interactions and the induced electromagnetic attraction force when an incident electromagnetic wave with enhanced intensity acts on the DSRR. Low-loss liquids including polyalphaolefin and polydimethylsiloxane are used in this paper as the host media to clearly show the electromagnetic resonance and its resonance shift performances. These experimental investigations and the obtained results can create a completely different research direction for the application of metamaterials in liquid-phase environments.

Optimization of a Low-Voltage Load Switch for a Smart Meter Based on a Double Response Surface Model

The existing electric energy meter load switches have issues such as a low electrical life, poor resistance to short-circuit currents, high contact point resistivity and severe heating. Research has thus been conducted on the optimization of the electric energy meter built-in load switch mechanism to establish a double response surface model for the electromagnetic attractive force and reed reaction force. The model introduces a niche fitness sorting strategy and a Gaussian mutation mechanism that are based on the standard particle swarm algorithm and form an improved multi-objective particle swarm optimization algorithm in which the static attractive force is regarded as the optimization objective. The multi-objective optimization of the structural parameters of the electromagnetic system and the reed system was carried out, and the optimization results were applied in the devices’ design and implementation. The new structure improves the electromagnetic suction and reed force at the suction position. And the results from simulation show that the proposed method exceeds that of the back propagation neural network method in achieving the optimization goal and the new structure can effectively improve the performance of meter built-in load switch by avoiding the recoil phenomenon.

電磁吸引力を用いたアクチュエータにおける変位拡大率と動作時間の関係の実験的検証

Displacement amplified electromagnetic actuators are developed for efficient use of the electromagnetic attractive force by applying displacement amplification mechanisms. Although these actuators are expected to realize faster drive than actuators directly using the electromagnetic attractive force without displacement amplification, both theoretical and experimental verifications have not been conducted yet in detail. This paper introduces an experimental verification of the effect of amplification ratio to the actuation time. A measurement system for the experimental verification was developed. The results of the experiment showed that application of displace amplification to the electromagnetic attractive force reduces the actuation time under the adequate conditions.

A Novel Electromagnetic Actuator Based on Displacement Amplification Mechanism

This paper introduces a new type of linear actuator using the electromagnetic attractive force, which enables a submillimeter stroke. In general, actuation by the electromagnetic attractive force causes a tradeoff problem between the thrust force and the stroke because the thrust force depends on the gap between the electromagnet and the armature; an increase in the gap (stroke) drastically degrades the thrust force. To realize a submillimeter stroke while retaining a high thrust force, a structure that adopts a displacement amplification mechanism is proposed, which is often used to expand the stroke of a piezoelectric actuator. First, the electromagnetic attractive force is theoretically examined with and without displacement amplification. We verify that displacement amplification could create a higher thrust force and energy efficiency over a certain displacement. On the basis of this examination, a prototype actuator is designed, and the driving principle is illustrated. Further, an analytical model of the proposed actuator is developed for control and performance estimation. Several fundamental experiments with a developed actuator are performed in order to reveal the potential of the proposed actuator. The performance evaluations show that the maximum stroke is approximately 450 μm and a bandwidth greater than 300 Hz can be realized, and more a time constant is approximately 2 ms for a stroke of 450 μm. In addition, the experimental results were compared with the simulation results calculated from the analytical model to verify whether the prototype drives predictably according to the proposed concept under a dynamic situation. These results demonstrate that the proposed actuator enables good actuation performance, and it implies that there are tremendous advantages from the viewpoints of manufacturing, assembly, control, etc.

Performance Improvement in the Axial Flux-Segmented Rotor-Switched Reluctance Motor

Axial flux-segmented rotor-switched reluctance motor (SSRM) topology could be a potential candidate for in-wheel electric vehicle application. This topology has the advantage of the increased active surface area for the torque production as compared to the radial flux SSRM for a given volume. To improve the performance of axial flux SSRM (AFSSRM), various stator slot/rotor segment combinations and winding polarities are studied. It is observed that the torque ripple is high for the designed three-phase, 12/8 pole AFSSRM. Therefore, the influence of the stator pole and rotor segment arc angles on the average torque and the torque ripple is studied. In addition, the adjacent rotor segments are displaced with respect to the stator, to reduce the torque dips in the phase commutation region. The proposed arrangement is analyzed using the quasi-3-D finite-element method-based simulation study and it is found that the torque ripple can be reduced by 38%. Furthermore, the low-frequency harmonic content in the torque output is analyzed and compared. The variation of the axial electromagnetic attractive force with displaced rotor segments is discussed. The effectiveness of the proposed technique is verified experimentally.

Failure Mechanism Analysis of Electromagnetic Relay under Mechanical Impact

The aim was to analyze failure mechanism of electromagnetic relay caused by mechanical impact. The principle of electromagnetic relays was studied and the effect of mechanical impact on electromagnetic relays was analyzed in this paper. Based on the established magnetic circuit model, the relationship of the magnetic field strength, the electromagnetic attraction and the impact damage degree was studied. Then, the damage intensity of mechanical impact on magnetic circuit was decided. Afterwards, the structure of electromagnetic relays was improved, and the mechanical impact simulation was studied by ANSYS. The results show that the uncontrollability of electromagnetic relay is mainly caused by air gap, which is aroused by mechanical impact; in addition, the size of air gap is inversely proportional to electromagnetic attraction force. Moreover, the improved structure of relays can increase impact resistance and broaden the scope of engineering application of electromagnetic relay.

Innovative servo gap-retainer design by applying electromagnetic attraction force

A TDOF (Two Degrees of Freedom) Servo Gap-Retained Mechanism (SGRM) is proposed and verified by experi- ments in this work. It mainly consists of a flywheel and an Intelligent Posture Tracking System (IPTS). The flywheel, driven by an induction motor for spinning, is regarded as the tracking objective of the IPTS. The IPTS is mainly composed by an intelligent disc and the Hybrid Magnetic Actuators (HMAs). The posture of the intelligent disc is controlled by the magnetic forces induced by the HMAs to retain a constant gap with respect to the eccentric flywheel which spins, tilts and wobbles. Since the HMA is highly nonlinear, a Feedback-Linearized Sliding Mode Control (FLSMC) is synthesized to account for system pa- rameter nonlinearities or unmodeled dynamics. The dynamics of the flywheel and the IPTS are theoretically investigated and analyzed. In fact, the proposed SGRM is a part of an entire flywheel cell. That is, once the MGU (Motor/Generator Unit) in fly- wheel cell operates at idle mode, the shaft of flywheel will be separated apart from MGU in order to avoid the energy loss of the flywheel by the back EMF induced by the magnetic field of MGU. On the other hand, the shaft of flywheel and MGU still need to maintain synchronous power transmission even at idle mode so that a non-contact clutch is equipped. Generally speaking, the role of SGRM in a flywheel cell is to ensure the centerline of the flywheel properly aligned with the non-contact clutch. At last, intensive computer and experimental simulations are undertaken to verify the feasibility of the proposed SGRM and FLSMC. It is evidently showed that the proposed SGRM under FLSMC exhibits superior transient response and servo capability upon constant gap retained. The steady-state tracking errors are about 5% with respect to the amplitudes of the reference trajectories in two radial directions (i.e., X-axis and Y -axis).

Experimental Study on Electromagnetic Force Induced Vibration and Noise from Universal Motor with Off-Centered Rotor

There are many harmonic components in the electromagnetic force caused by electrical motors. The harmonic components induce the structural vibration and noise, frequently. The amplitude of harmonic components is also affected by magnitude and angle of the eccentricity of rotor. The unbalanced electromagnetic attractive force is generated between the rotor and the stator when the rotor is not corresponding to the center of the stator, that is, eccentric in the electrical motor. The unbalanced electromagnetic attractive force causes vibration and noise. In the paper, electromagnetic vibration and noise from universal motor with rotor eccentricity are experimentally discussed comparing with normal rotor. The magnitude of eccentricity is 0.2mm against air gap 0.4mm and, angle of eccentricity is 0, 45, 90, and 135 deg. The vibration and the noise of the motor grow by the frequency of the electromagnetic force agreement with structural natural frequency, that is, resonance. As for eccentricity magnitude 0.2mm and the angle 90 deg, maximum value of vibration amplitude doubles roughly and the noise is about 9 dB larger than those of normal motor. The amplitude of vibration and noise depend on eccentric angle. The vibration and the noise depend on the angle of rotor eccentricity.

BLDC 모터를 적용한 로터리 컴프레서 소음 저감에 관한 연구

The main noise and vibration source of the BLDC rotary compressor for air conditioner was analyzed by using the measurement of noise and vibration, noise contour, and experimental modal analysis. The source is presumed to the mechanical resonance excited by the electromagnetic attractive force of the BLDC motor. To reduce the excessive noise of the BLDC rotary compressor due to the mechanical resonance, air-gap enlargement and structural dynamic modification were applied in this paper. Its validations were conducted by the analysis of the electromagnetic attractive force which is generated by the BLDC motor and by the measurement of noise and vibration of the BLDC rotary compressor. By enlarging the length of air-gap and conducting the structural dynamic modification, the noise and vibration in the compressor was significantly improved by 4.5 dB(A) and 56 percent, respectively.

Numerical simulation of magnetic flux and force in electromagnetic forming with attractive force

The electromagnetic forming process with electromagnetic attractive force can cover the disadvantage of that with electromagnetic repulsive force and expand its applications. In this paper, the principle of electromagnetic attractive force forming is proposed and the effect of the discharge current waveform on the direction of electromagnetic force acting on the workpiece is discussed. The FEA software ANSYS is used to simulate the distributions of magnetic flux and magnetic force with flat coil. The numerical simulation results indicate that the improved discharge current which ascends slowly, descends quickly, and descends slowly in turn is more suitable for the process of electromagnetic attractive force forming. A simple test basing on the principle of electromagnetic attractive force is presented and the experiment shows that the attractive force can be realized successfully.

Static and Dynamic Analysis for Contactor with a New Type of Permanent Magnet Actuator

SUMMARY A new type of permanent magnet actuator driven by elec-tromagnetic repulsive force in breaking course and electromagnetic attrac-tion force during closing course is presented in this paper, and the staticand dynamic characteristics for contactor with this new type actuator aremainly focused on by simulation and experiment simultaneously. Firstly,the static electromagnetic attraction force in closing course and electromag-netic repulsive force in breaking course are studied by FEM simulation andexperiment. Secondly, by coupling of the electrical and mechanical dif-ferential equations, the dynamic electromagnetic attraction force in closingcourse and dynamic electromagnetic repulsive force in breaking course areobtained respectively. Thirdly, by constructing the mechanical model ofcontact system and permanent magnet actuator, the displacements of mov-ing contact and moving core while both contactors’ closing and breakingare obtained by simulation and experimental study. It is indicated that sim-ulation results coincide well with that of experiment.

826 電磁力による走行柔軟磁性体の非接触案内に関するモデリング

In a processing facility, the plate usually travels at a velocity of more than 10m/s. When a long steel plate travels at high speed, rollers are usually used as supporters. However, when rollers are used, deterioration caused by cracks in the process of coating or gilding is possible. We have proposed noncontact guide by using electromagnetic attractive force for a traveling steel belt. In this study, modeling for the system was presented. To verify the usefulness of the modeling, control experiment and simulation were performed.

Vacuum interrupters with axial magnetic field contacts based on bipolar and quadrupolar design

Axial magnetic field (AMF) contacts are applied within vacuum interrupters especially for high short-circuit currents. In this paper, two AMF contact designs based on a bipolar and a quadrupolar magnetic field arrangement and their characteristics are presented. In the first section, both principles are discussed. This is followed by three-dimensional field simulations performed by means of a finite-element-analysis program. The magnitude of the axial magnetic flux density, the phase shift between current and magnetic flux density, and the residual AMF after current zero are investigated during arcing with a constant contact gap. Furthermore, the influence of motion during the contact opening on the previously-mentioned parameters is investigated. An important parameter during the design phase of AMF electrodes is the electromagnetic attractive force, which is provided by the AMF contacts during current flow. This force can reduce the required contact force provided by the drive of the vacuum circuit breaker. Finally, it is reported about the short-circuit performance of both contact systems. Contact plates after high-current interruption are presented revealing the arcing behavior during the high-current phase.

Mobile micro-robot in small pipe driven by electro-magnetic force

It is required to develop micro-machine for inspection and maintenance of defects inside small pipe with diameter smaller than one inch. Considering the advantages of electromagnetic actuators with simple mechanism, high response, convenience to control and fabricate, we tried to develop a new micro-robot in small pipe based on interaction principle of electromagnetic attraction and spring force. This paper describes its structure and design. The dimension of the prototype is diameter of 15 mm, length of 30 mm and weight of 25 g. It can climb in small pipe of diameter of 20 mm with a speed of 6∼8 mm/s in horizontal or in vertical situation.

Some Considerations on Electromagnetic Vibration in a LIM for a Train

This paper considers the generation of noise in a linear induction motor (LIM) used in a linear motor car. Frequency analysis of the electromagnetic vibration established that the noise in the LIM was generated mainly by the electromagnetic attractive force between the primary member and the reaction plate (RP) and that also by high-frequency flux due to the input current supplied from a VVVF inverter.