Magnet Research Articles

Study on the Application of Vibration Energy Harvester Based on 3D Chip-scale Solenoids Coil in Rail Transit

Introduction: A 3D chip-scale solenoid coil was fabricated by micro-electro-mechanical system (MEMS) and wafer-level micro casting technology, and an electromagnetic vibration energy harvester was manufactured with an NdFeB permanent magnet. Methods: Three coils with different turns were designed, namely 45 turns, 90 turns, and 150 turns. The coils had a wire width of 40 microns, a pitch of 25 microns, and a thickness of 150 microns. The permanent magnet was cylindrical with a diameter of 1.8 mm. According to the length of the coil, three specifications of 3/6/10 mm were selected for the permanent magnet. Special PCB circuit testing tooling was processed to test the actual performance of three kinds of permanent magnet energy harvesters with different specifications. Results: The vibration frequency was set to 10 Hz~150 Hz, and the acceleration was designed to be 50 m/s2~300 m/s2. For the energy harvester with 90 turns, a maximum output power of 75 μW was obtained under vibration conditions of 100 m/s2 & 30 Hz. The experimental data showed that vibration frequency, acceleration, and sample size had a certain influence on the energy conversion and output power of vibration. Conclusion: Through the above study, the design and performance of vibration power generation devices can be optimized better to match the actual application requirements of rail transit.

Severe plastic deformation of Mn-Al permanent magnets

Manganese-aluminum permanent magnets are promising candidates to fill the cost and performance gap between lower-performance bonded ferrites and high-performance magnets based on rare-earth elements. This is due to the favorable combination of saturation magnetization and magnetocrystalline anisotropy in the Mn-Al τ phase combined with low raw material cost. However, the τ phase is metastable and prone to decomposition at high temperatures, making processing by conventional milling and sintering difficult. Severe plastic deformation (SPD) is an alternative processing route to control the microstructure of a material by applying very high amounts of strain. In this study, equal-channel angular extrusion (ECAE) and high-speed high-pressure torsion (HS-HPT) were both tested as SPD processing routes. ECAE improved magnetic energy product, (BH)max, by 220% by refining the grain size and imparting a high density of dislocations. HS-HPT enabled a rapid phase transformation from the high-temperature ε phase to the τ phase but lowered Hci, making it better suited to soft magnet processing.

Pre-magnetization smashing hydrated vanadium ions to improve redox flow batteries performance

The vanadium redox flow battery (VRFB) has received extensive attention due to its intrinsic safety and high scalability. Currently, there are still deficiencies of low energy efficiency and higher unit capacity cost in VRFB energy storage. Continuously optimizing the battery performance through reducing electrode polarization losses is a necessary way to achieve efficient VRFB energy storage technology. In this study, a method of pre-magnetizing the electrolyte to improve the performance of the battery was proposed. A permanent magnet with an intensity of 0.9 T was used to pre-magnetize the vanadium-ion aqueous electrolyte before feed into the battery stack and working-on, it was found that the diffusion capacity of vanadium ions increased by 133.6 % after pre-magnetized even if the external magnetic field was removed. Meanwhile, both of the charge transfer and concentration polarization resistance of the electrode were reduced. The energy efficiency (EE) of the battery was increased by 6.4 % in the charge–discharge test at current density of 300 mA cm−2. The power density increased by 6.19 % with current density 400 mA cm−2 at most, and it prefers to continuously increase as current larger. The electrolyte pre-magnetization showed significant positive improvements on the electrode reaction kinetics and battery charge–discharge cycle.

High-abundant rare earth La/Ce substituted Nd2Fe14C based permanent magnet materials prepared by mechanochemical method

To balance the utilization of rare-earth resources and reduce the preparation cost, the La and Ce substituted Nd2Fe14C hard magnetic alloys were prepared by a facile mechanochemical method for the first time. A two-step process is typically employed: 1) Decomposition of hydrocarbon and disproportionation of (Nd1-xREx)2.5Fe14B0.08 (RE=La or Ce, x=0-0.3) alloys during high-energy ball milling, Nd+Nd2Fe17+n-hexane→NdH2+δ+α-Fe+Fe7C3; 2) (Nd, RE)2Fe14C hard magnetic powders were obtained via the vacuum annealing at 800 °C for 2min. The phase relation, magnetic properties and microstructural evolution of (Nd, RE)2Fe14B0.08C0.92 (named Nd-RE-Fe-C-based) alloys were systematically investigated. Substitution of La for x=0.1 Nd in the Nd-RE-Fe-C-based alloy increase the coercivity from 15.6kOe to 18.6kOe without reducing the remanence. First-principles calculation was performed to study the mechanism of magnetic properties La and Ce substituted samples. The results showed that La tends to be expelled from 2:14:1 phase to form more minor phases which act as the domain wall pinning center, increasing the coercivity. However, Ce prefers to enter the 2:14:1 phase, diminishing the permanent magnetic properties due to the poor intrinsic magnetic properties. This paper provides a novel viewpoint for the effective utilization of high abundant rare earth and the investigation of low cost Nd2Fe14C permanent magnet materials.

Design comparison of surface-mounted permanent magnet synchronous motors with inner and outer rotor configurations

Design comparison of surface-mounted permanent magnet synchronous motors with inner and outer rotor configurations

The Process of Stacking a Conductor with Current Within the Interpolar Line of a Permanent Magnet

The Process of Stacking a Conductor with Current Within the Interpolar Line of a Permanent Magnet

Reduction of torque ripples using the DTC-SVM method in PMSM with extended Kalman filter

A detailed analysis has been conducted on two motor control algorithms: direct torque control (DTC) and field-oriented control (FOC). There are two ways that a voltage source inverter (VSI) can regulate a permanent magnet synchronous motor (PMSM). When using the PMSM and voltage source inverter (VSI), dead time is employed to turn off both the upper and lower switches to prevent short circuits. However, by supplying the PMSM with unexpected polarity voltages at the VSI output voltage, this switching technique reduces distortion. It is challenging to utilize the sensor to directly detect the fault voltage that results in an open circuit. This work examines the nonlinearity of the electric power controller during dead time during PMSM operation using the DTC algorithm to increase control stability. The stress distribution is estimated using an extended Kalman filter (EKF). Ultimately, the model presented in this study verified the increase in stator current and torque output through simulations and testing.

Mechanical modulation wave energy harvesting for self-powered marine environment monitoring

Small-scale wave energy harvesting can be used for self-powered marine environmental monitoring, with the advantages of sustainability, convenience, and environmental protection. The low-frequency and strong random fluctuations of ocean wave motion are not conducive to electromechanical conversion. In this paper, we propose a mechanically modulated wave energy harvester embedded with interference-free triboelectric nanogenerators. The mass pendulum oscillates under irregular low-frequency wave excitation, and then the oscillation is mechanically modulated into a unidirectional high-speed rotation of four permanent magnet disks. The elastic parts on both sides of the mass pendulum are functionalized into multi-layered folding triboelectric nanogenerators, which neither increase the volume of the wave energy harvesting system nor affect the operation of the electromagnetic generator. The prototype was manufactured and the experimental results show that the sum of the average power of the prototype is 4.8 W under excitation at a frequency of 3 Hz and a inclination angle of 40°. The 0.47 F capacitor can be charged to 5 V in 80 seconds by the prototype under the wave excitation generated by push plate, and then used for self-powered marine environmental monitoring (illumination, temperature and pH) and wireless information transmission.

Performance analysis of field oriented controlled PMSM based electric truck

The electric vehicle (EV) concept is considered the ideal solution to save the environment from pollution occurring due to internal combustion engines or ICE-based vehicles. However, electric power trains have found more penetration in the segment of passenger vehicles and electric buses. This paper presents the performance of an electric truck. Field-oriented controlled permanent magnet synchronous motor (PMSM) is used for the powertrain of the proposed electric truck. The performance of the proposed electric truck is analyzed for propulsion as well as regenerative mode of operation using MATLAB. The effect of different gradient conditions of the road surface on the behavior of the proposed truck is observed. The presented simulation results depict the satisfactory operation of the proposed PMSM-driven electric truck for various operating conditions.

Integrated electric vehicle design and simulation: Combining a mechanical and electrical model using Simscape/Multibody

This paper presents a novel methodology for modeling and implementing an electric vehicle (EV) simulation model using the Multibody approach. The proposed method provides a robust solution for studying EV performance, taking into consideration the dynamic behavior of its complex mechanical system. The mechanical design was carried out using SOLIDWORKS software and then exported to the Simscape/Multibody platform. This process was performed to combine the obtained mechanical design with an electrical model, developed using the Simscape and MATLAB/Simulink toolbox, in the same simulation platform. The proposed EV is powered by an electromechanical PowerDrive based on a permanent magnet synchronous machine (PMSM), supplied by a hybrid energy storage system (HESS). The implemented HESS, operating in a fully active topology, is controlled by a deterministic rule-based energy management system (EMS). To evaluate the proposed model performance, simulations were conducted under ECE-15.

Reduction of Torque Oscillations in Permanent Magnet Synchronous Machine Using Optimal Current Injection Based on Unbalanced Load Detection

Reduction of Torque Oscillations in Permanent Magnet Synchronous Machine Using Optimal Current Injection Based on Unbalanced Load Detection

Modeling and Analysis of a Novel Distributed Magnetic-Pole Permanent Magnet Planetary Machine

Modeling and Analysis of a Novel Distributed Magnetic-Pole Permanent Magnet Planetary Machine

Sensorless Position Control in High-Speed Domain of PMSM Based on Improved Adaptive Sliding Mode Observer

To improve the speed buffering and position tracking accuracy of medium–high-speed permanent magnet synchronous motor (PMSM), a sensorless control method based on an improved sliding mode observer is proposed. By the mathematical model of the built-in PMSM, an improved adaptive super-twisting sliding mode observer is constructed. Based on the LSTA-SMO with a linear term of observation error, a sliding mode coefficient can be adjusted in real time according to the change in rotational speed. In view of the high harmonic content of the output back electromotive force, the adaptive adjustment strategy for the back electromotive force is adopted. In addition, in order to improve the estimation accuracy and resistance ability of the observer, the rotor position error was taken as the disturbance term, and the third-order extended state observer (ESO) was constructed to estimate the rotational speed and rotor position through the motor mechanical motion equation. The proposed method is validated in Matlab and compared with the conventional linear super twisted observer. The simulation results show that the proposed method enables the observer to operate stably in a wide velocity domain and reduces the velocity estimation error to 6.7 rpm and the position estimation accuracy error to 0.0005 rad at high speeds, which improves the anti-interference capability.

Derivation of a general and explicit equation for the force between identical cylindrical permanent magnets with the help of Wolfram|Alpha application

Abstract Until recently, there has been no single, explicit equation that explains how force between identical permanent magnets varies with distance over any distance. Typically, observation data is fitted using two curve segments: at large and small distances. In this work, we derive a general equation to determine the force between identical cylindrical permanent magnets at any distance with the help of the Wolfram|Alpha application to get the explicit form of an integral problem introduced by Vokoun et al (J. Magn. Magn. Mater. 321 3758–63, 2009) that appears to have no analytical solution. The resulting equation accurately fits observational data and can be used to estimate the magnetization of permanent magnets.

Self-Powered Pressure Sensor Based on Flexible Permanent Magnet Material

Self-Powered Pressure Sensor Based on Flexible Permanent Magnet Material

Extreme learning machine‐based super‐twisting integral terminal sliding mode speed control of permanent magnet synchronous motors

AbstractThis article proposes an extreme learning machine (ELM)‐based super‐twisting integral terminal sliding mode control (STITSMC) for speed regulation of a permanent magnet synchronous motor (PMSM). First, the PMSM is modeled in a non‐cascade control structure for fast system response and uncertainty compensation in the speed and torque loops. Second, the STITSMC is designed with integral actions in both the sliding surface and the reaching law to reduce chattering. Third, the ELM is constructed to compensate for the system lumped disturbance, and relax the disturbance upper bound required by the controller which further reduces the chattering. Fourth, the stability of the whole control system is proved based on the Lyapunov method and the finite time convergence regions are derived for both the reaching and the sliding phases. Finally, the comparative simulations and experiments are conducted to show the superiority of the proposed control.

A new ultra-compact communications system across air-sea water based on ELF magnetic mechanical antenna

Abstract In this paper, a long-range trans-air-seawater medium communication system is proposed based on a small extremely low-frequency (ELF) mechanical antenna. We analyze the propagation characteristics of ELF electromagnetic waves in seawater and determine the paths of ELF electromagnetic waves propagating across domains. Equivalent models of various mechanical antennas are analyzed based on their operating principles. Based on the equivalent model, the transmission principle of mechanical antenna in transmitting across air-sea medium is analyzed, and finally the mechanical antenna with permanent magnet working horizontally is identified as the optimal choice. The above results are also verified by simulation. Experimental and simulation results verify the good performance of a horizontally operating permanent magnet mechanical antenna in transmitting across air-sea medium. The ELF-band transmission communication across air-sea medium based on binary code modulation is realized, and the farthest transmission distance can reach 200m in the experiment. Based on this system, transmission in air was also tested up to a distance of 1.5 km. The ELF transmission across air-sea medium based on a permanent magnet mechanical antenna can greatly facilitate cross-domain teleportation and ocean exploration.

Liquid-liquid extraction and separation of light and heavy rare earth elements from chloride solution using a mixture of tertiary amine and phosphinic acid: recycling strategies for NdFeB magnet

ABSTRACT This piece of work aims to study the extraction behavior of light and heavy rare earth elements, which are often found in permanent magnets, using a mixture of tri-octyl amine and bis-(2,4,4-trimethylpentyl) phosphinic acid from a chloride medium. The study showed that the extraction efficiency of Dy(III) is more than that of Nd(III) and Pr(III). Benzene proved to be an effective diluent. Increasing the pH of the aqueous phase improved the extraction percentages, with maximum extractions of 98.4% for Dy(III), 61.2% for Nd(III), and 58.3% for Pr(III) at pH 5.04 using 0.1 mol/L of each extractant. Adding sodium chloride enhanced the extraction efficiency due to the salting-out effect. The extraction mechanism has been proposed based on the slope analysis and FTIR data. From thermodynamic variables, the process was found to be exothermic. The simulated leach liquor of NdFeB magnets showed the highest separation factors of 67.7 (Dy/Pr) and 56.9 (Dy/Nd) at pH 2.05 with 0.25 mol/L extractants. The counter-current study showed that 4.15 mg/L Dy(III) was left behind in the raffinate indicating 97.4% removal of Dy(III) in two stages at unity phase ratio. Testing with actual leach liquor from hard disk magnets revealed a preference for iron extraction, which impeded REE extraction.

Ocean current turbine power take-off design using fluid dynamics and towing tank experiments

This study investigates the performance and power generation capabilities of a small-scale hydrokinetic turbine by comparing numerical simulations with experimental measurements. The key difference between the two models comes from the initial numerical analysis which focused only on the permanent magnet DC motor (PMDC) motor’s parameters and did not account for the gear-head reduction that leads to discrepancies in current and torque predictions, especially at lower input voltages. In practice, friction losses within the gear-head increased the required current and torque, highlighting inefficiencies in the motor gear-head system. A modified experimental setup incorporated a magnetic coupling to address leakage issues and enhance system reliability. While the magnetic coupling resulted in a slight reduction in speed, current, and torque, it improved the overall integrity of the system which is essential for marine applications. The comparison between experimental results and Blade Element Momentum (BEM) simulations showed good agreement at lower speeds, but the simulations under-predicted power at higher speeds, likely due to the model’s limitations in capturing complex hydrodynamic phenomena. This shows the need for comprehensive analysis, integrating both numerical and experimental approaches to optimize turbine performance. Future research will focus on refining experimental methodologies and further improving turbine design and efficiency for hydrokinetic energy systems.

Cooling Enhancement of Axial Flux Permanent Magnet Motors by Corrugated Spiral Channels with Nanofluid

Cooling Enhancement of Axial Flux Permanent Magnet Motors by Corrugated Spiral Channels with Nanofluid