International Journal of Applied Electromagnetics and Mechanics - Volume Pre-press, issue Pre-press

Authors: Guo, Rong | Yu, Haitao | Wang, Yao | Chen, Hao | Liu, Xiaomei | Xia, Tao

Article Type: Research Article

Abstract: Permanent magnet synchronous linear motors (PMSLMs) have been widely used in industry applications due to their outstanding dynamic characteristics and improved servo-capability. However, the detent force of PMSLM is an inevitable problem, which causes vibration and affects the positional accuracy of the machine. An improved PMSLM structure with arc-teeth and inner-ladder end teeth (AIL-teeth) is proposed in this study to reduce detent force. This structure is advantageous because it not only reduces detent force but also keeps motor size constant. First, the parameters that affect detent force are confirmed using Fourier analysis method. Second, a hybrid optimization method is adopted …to obtain the structural parameters of the AIL-teeth PMSLM. The hybrid optimization method is based on the flux-tube and Taguchi methods. The optimal structural parameters of the AIL-teeth PMSLM are determined using the optimization method. Finally, two PMSLMs with traditional and improved structures are contrasted by finite-element analysis (FEA) method and experimental verification, results show that the improved AIL-teeth PMSLM can reduce detent force effectively with the least sacrifice of electromagnetic performance. Show more

Keywords: Detent force minimizes, AIL-teeth PMSLM, flux-tube method, Taguchi method, FEA method

DOI: 10.3233/JAE-180047

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-17, 2018

Authors: Zhai, Luxin | Han, Bangcheng | Liu, Xu | Zhao, Jianhui

Article Type: Research Article

Abstract: Magnetic-bearing reaction wheel (MBRW) can be applied to stabilizing satellites with stringent pointing accuracy. Temperature rise subjected to losses is a key issue for a MBRW. The prediction models of iron loss and copper loss for magnetic bearings and BLDCM are established, and the loss coefficients of iron core are determined by measured loss curves at different frequencies. The copper loss distribution and iron loss distribution of the MBRW are investigated. Based on the loss values, the heat generation rates of the different parts in the MBRW are calculated, then the thermal field of the prototype is analyzed by 3-D …finite element model. Thermal-structure coupled analysis of rotor is also investigated. Finally, the prediction and analysis of losses are verified by experimental results in a prototype of MBRW with rated speed of 5000 r/min and rated angular momentum of 15 Nms. Show more

Keywords: Magnetic bearing flywheel, iron loss, magnetic bearing, BLDCM, finite element model

DOI: 10.3233/JAE-180049

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-20, 2018

Authors: Zhang, Bo | Lu, Ping | Kong, Jinjiao | Liu, Rui | Cao, Quanliang | Shao, Hongbo | Deng, Wanting | Chen, Jun

Article Type: Research Article

Abstract: An actual occurred ground-fault accident of 500 kV transformers in HVDC converter station is presented. A 2D transient electromagnetic-thermal-mechanical finite-element coupling model of 500 kV transformer is developed to analyze the transient process of failure, with consideration of the resistance-temperature relationship and plasticity displacement in the windings’ thermal and mechanical characters. To verify the proposed finite-element model, the model is calibrated by pre-fault field test of the transformer in steady state, which shows good agreement with measurement. The short-circuit current adopted in simulation is based on actual on-site measurement of the ground-fault accident. By using the proposed model, simulation results …reflect the transient process and explain the post-fault inspected damage well in term of over burn regions in thermal analysis and deformation tendency in mechanical analysis when compared with field post-fault inspection photos. Show more

Keywords: Electromagnetic analysis, finite-element, transformer, ground-fault accident and DC grid

DOI: 10.3233/JAE-180082

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-12, 2018

Authors: Wang, Siqi | Liu, Yongkai | Li, Decai | He, Xinzhi

Article Type: Research Article

Abstract: This paper proposes a ferrofluid-based tuned mass damper with magnetic spring that is capable of absorbing the low-frequency vibration energy. The characterization and performance of the tuned mass damper are studied in theory and experiment. Ferrofluid is adhered on the moving permanent magnet and used as self-sustained viscous lubricant to reduce the mechanical damping between the permanent magnet and the inner wall of plastic tube and improve the ability of the vibration pick-up system. A magnetic spring is formed by magnetic repulsive force between the fixed and the moving permanent magnets along the horizontal axis. The tuned mass damper can …effectively reduce the low frequency vibration of the rod. And the damping time in the cases of released permanent magnet is 1/6 times as long as that in the cases of blocked permanent magnet. The compact tuned mass damper with adjustable damping and stiffness is suitable to various low frequency vibrations in nature. Show more

Keywords: Ferrofluid, magnetic spring, damper, vibration

DOI: 10.3233/JAE-180056

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-7, 2018

Authors: He, Xinzhi | Wang, Li | Yu, Jun | Li, Decai

Article Type: Research Article

Abstract: Magnetic fluid seal is the most important and mature application of magnetic fluid. Usually, gravity is ignored when analysing the performance of magnetic fluid seal and designing magnetic fluid sealing devices. With the expansion of magnetic fluid seal applications, gravity could seriously affect the performance of magnetic fluid seal, especially when the “O” ring diameter of magnetic fluid and sealing gap are both large. In this paper, the influence of gravity on the anti-pressure ability of magnetic fluid seal is theoretically analysed and proven by the experiments. The results show that magnetic fluid seal has a limit size that is …directly proportional to the magnetic field gradient in the sealing gap and is inversely proportional to the ratio of magnetic fluid density to the magnetization. If the diameter of the magnetic fluid “O” rings, whose centre axis is perpendicular to the direction of gravity, is far smaller than the limit size, the influence of gravity on the anti-pressure ability of magnetic fluid seal can be neglected. However, if the size is close to or greater than the limit size, gravity would lead to a drop in the anti-pressure ability of magnetic fluid seal. Show more

Keywords: Seal, magnetic fluid, gravity, sealing limit size, anti-pressure

DOI: 10.3233/JAE-180054

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-12, 2018

Authors: Mehboob, Nasir | Nasir, Muhammad Farooq | Grössinger, Roland | Oser, Peter | Kriegisch, Martin | Fulmek, Paul

Article Type: Research Article

Abstract: Frequency and temperature dependence of the hysteresis loops (both major and minor hysteresis loops) of well-known materials such as pure Fe and pure Ni in the as-cast state and after a heat treatment, were measured and analyzed. Furthermore temperature dependent magnetostriction of the as-cast and annealed Ni sample were measured and residual stresses were estimated by assuming the magnetoelastic energy as the origin of coercivity H c . The hysteresis measurements were made on fully automized hysteresigraph which is handled by a labview program. The system works with ring- or frame-shaped samples in the frequency range from 0.1 Hz to …2 kHz and in the temperature range from −77 K to 493 K. Show more

Keywords: Magnetic hysteresis, coercivity, residual stresses, magnetostriction

DOI: 10.3233/JAE-170075

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-8, 2018

Authors: Wang, Shen | Huang, Songling | Wang, Qing | Wang, Zhe | Zhao, Wei

Article Type: Research Article

Abstract: In this work a multiphysics model of a meander line electromagnetic acoustic transducer (EMAT) to generate S0 mode Lamb waves in an aluminum plate is built and the structural parameters of the transducer are optimized based on the model. Three approaches to solve the amplitude of the in-plane displacement component at an observation point are explored and the single frequency approach is selected because it is the fastest. In the optimization, the objective function to minimize is the negative amplitude of the S0 mode waves, and the design variables are the width and height of the magnet and liftoff values …of the magnet and the coil from the top surface of the plate. The liftoff values form a linear constraint of the optimization problem. A genetic algorithm (GA) program capable of handling the linear constraint efficiently is developed. The internal status of the GA program is tracked carefully to avoid unnecessary evaluations of the objective function. With 30 runs of the program, the optimal set of variables leads to the ratio of the width of the magnet to that of the coil of 115.85%. Show more

Keywords: ultrasonic transducers, meander line electromagnetic acoustic transducers, Lorentz force, Lamb waves, constrained optimization

DOI: 10.3233/JAE-180086

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-15, 2018

Authors: Tao, Yaqin | Wang, Jingang | Xu, Zhi

Article Type: Research Article

Abstract: A double differential D-dot overvoltage sensor is proposed based on the D-dot principle for the purpose of faster and more accurate measurement of overvoltage signals. The proposed sensor is a new D-dot sensor structure consisting of four electrodes. It is applied together with the double differential input structure. This structure allows the sensor to operate in self-integration mode and achieve a wide frequency response characteristic while has a stronger anti-interference capability. The simulation demonstration and parameter design are carried out by using the Ansoft Maxwell. A test platform is constructed and used in the steady-state performance and lightning impulse transient-state …test of the sensor. Test results demonstrate that the double differential D-dot sensor has satisfying steady-state performances, manifested by small measurement phase and amplitude errors. It can be applied to internal overvoltage measurement of power system. Moreover, the double differential D-dot sensor is equipped with good transient characteristics. The relative error of the lightning wave rise time which is measured by the double differential D-dot sensor is controlled in the range of ±1.7% and the relative measurement error of lightning wave peak is smaller than ±2.0%. It can measure external overvoltages effectively. Show more

Keywords: Double differential input, D-dot sensor, overvoltage signal measurement, non-contact, Ansoft Maxwell

DOI: 10.3233/JAE-180076

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-19, 2018

Authors: Yang, Xiaolong | Chen, Fan | Gao, Shanghan | Chen, Yanhui

Article Type: Research Article

Abstract: In order to meet the high cleanliness and high vacuum requirements of the working environment of the silicon conveyer robot, a new type of concentric biaxial stepped ferrofluid sealing structure is proposed based on the original universal ferrofluid sealing structure. The two dimensional simplified physical model of concentric biaxial stepped structure under axisymmetric condition is established by using the magnetic field finite element method. The nonlinear magnetic field distributions in the ferrofluid sealing structure are calculated and analyzed. The influences of the sealing gap, the width of the pole teeth, the ratio of the permanent magnet length to its height …on the its sealing capabilities were studied. The calculation results were also analyzed and discussed. The results show that the pressure resistances of the concentric biaxial stepped ferrofluid seals significantly decrease with the increase of the sealing gap. Their pressure resistances firstly increased and then decreased with the increase of tooth width. The pressure resistance of the outer diverging stepped ferrofluid seal in the concentric biaxial stepped ferrofluid seal firstly increased and then decreased with the increase of the ratio of the permanent magnet length to its height; Their pressure resistances of inner converging stepped ferrofluid seal firstly decrease and then increase with the increase of the ratio of the permanent magnet length to its height. Show more

Keywords: Silicon conveyer robot, Concentric biaxial stepped shaft, ferrofluid seal, key parameters, finite element method

DOI: 10.3233/JAE-180060

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-11, 2018

Authors: Zheng, Li | Qing, Chen | Yu, Xiao | Dixin, Wang | Leiyong, Wang | Qunjing, Wang

Article Type: Research Article

Abstract: Considering the influence of fluid structure interaction and cavitation on the actual deformation of hydrodynamic spherical bearing, the fluid-solid coupling analysis and multiphase flow simulation of spherical bearing for multi-degree-of-freedom motors are realized in this paper. The finite element simulation analysis of the model is carried out by using multi-physical field coupling software. In the study of bearings with and without effects of cavitation, the analysis shows that the peak value of oil film pressure and elastic deformation of spherical bearing decrease when cavitation effect is considered. The oil film pressure increases with the increase of eccentricity, rotation speed, viscosity …and the decrease of the clearance between stator and rotor, which improves the bearing capacity of the bearing, but also intensifies the cavitation in the oil film divergence area and increases the gas volume fraction. And the oil film pressure test platform with different rotational speeds of the spherical rotor is set up, the measured experimental data are in good agreement with the numerical results. In the practical application of the motor, appropriate parameters should be selected, which is helpful to improve the working condition of spherical bearings, ensure the stable operation of bearings and prolong the service life. Show more

Keywords: Spherical bearings, oil film pressure, cavitation, fluid-solid coupling

DOI: 10.3233/JAE-180064

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-19, 2018