International Journal of Applied Electromagnetics and Mechanics - Volume 13, issue 1-4

Authors: Didosyan, Yuri S. | Hauser, Hans | Reider, Georg A.

Article Type: Research Article

Abstract: Otherthoferrites are canted ferromagnets which exhibit extremely high domain wall (DW) velocities. The change of handedness in the DWs does not occur in Bloch lines but in lines of zero magnetization. Observations of the lines and of the DW inclinations in plates of yttrium orthoferrite are reported. The inclinations occur towards the direction of the crystallographic a axis and reach tens of degrees.

DOI: 10.3233/JAE-2002-333

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 13, no. 1-4, pp. 215-218, 2002

Authors: Nagaya, Kosuke | Tont, Feng-Ying | Murakami, Iwanori | Tai, Norio

Article Type: Research Article

Abstract: A differential motion restraint coupling is presented. In order to have strong torque, multi friction plates are installed in the friction unit of the device that involves magnetorheological fluid. Two permanent magnets lie on both sides of the friction unit. Hence, magnetic fluxes freeze the magnetorheological fluid. The friction discs have a number of slits in the radial direction, which generate torque due to shear forces between the frozen fluid and the slits. A design method …has been presented for the device. To validate the present design formulae, experimental tests have been carried out. Calculated results are in good agreement with the experimental ones. Show more

Keywords: torque, differential motion, device, coupling, magnetorhrological fluid, clutch

DOI: 10.3233/JAE-2002-335

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 13, no. 1-4, pp. 219-228, 2002

Authors: Yamazaki, Katsumi

Article Type: Research Article

Abstract: This paper presents a method to calculate efficiency of induction motors considering stray losses caused by stator and rotor slot ripple. The harmonic electromagnetic fields are calculated by the combined 3D-2D nonlinear time-stepping finite element analysis considering movement of the rotor to estimate the harmonic copper and iron losses. The calculated losses and efficiency is compared with the experimental results. It is clarified that the losses concentrate at the surface of the stator and the …rotor core and that the consideration of the time-harmonics caused by the rotor movement is indispensable to estimate the losses and the efficiency of the motor. Show more

DOI: 10.3233/JAE-2002-324

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 13, no. 1-4, pp. 229-234, 2002

Authors: Chiriac, H. | Lupu, N. | Takeuchi, A. | Inoue, A.

Article Type: Research Article

Abstract: Extensive magnetic studies on Nd_{90-x} Fe_{x} Al_{10} (x = 35 ∼ 50) amorphous alloys in the shape of both melt-spun ribbons with thicknesses between 25 and 150 μm and rods with diameters no larger than 3~mm prepared by mould casting and suction casting indicate a complex magnetic behaviour depending on the Fe content. The microstructure and magnetic properties are strongly dependent on the cooling rate and the preparation …technique. The high values of the coercive field of Nd_{90-x} Fe_{x} Al_{10} amorphous samples in the as-cast state as well as their increase by the decrease of the cooling rate and temperature result from the formation of very small metastable or non-equilibrium clusters, whose size vary as a function of the quench rate. The presence of these magnetic clusters is evidenced by multiphase magnetic transitions observed from the ac-susceptibility measurements at low temperatures. Show more

DOI: 10.3233/JAE-2002-331

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 13, no. 1-4, pp. 235-239, 2002

Authors: Caltun, Ovidiu Florin | Spinu, Leonard | Stancu, Alexandru | Sava, Anca

Article Type: Research Article

Abstract: Ferrites properties depend very strongly on the chemical composition and on the microstructure. The complex permeability spectra of Cu substituted Ni-Zn ferrites produced by conventional ceramic process for high frequency were studied. The experimental and theoretical curves of real and complex permeability were compared. Is discussed the contribution of the domain wall and of the spin rotational motion on the complex permeability in the MHz region. A small amount of Cu ions can provide high performances …to the Ni-Zn ferrite. Show more

DOI: 10.3233/JAE-2002-328

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 13, no. 1-4, pp. 241-244, 2002

Authors: Ohto, Motomichi | Ishikawa, Koji | Nose, Yukio

Article Type: Research Article

Abstract: An application of Finite Element Method for iron loss calculation is proposed. The motor iron loss is predicted by taking into account current ripple caused by PWM inverter power supply. This paper describes simulation method about iron loss under inverter drive system. In this method, drive system simulation is used to obtain the motor current waveform. The skin effect in the laminated core is considered by using results of two-dimensional magnetic field analysis. The method is …applied to an interior permanent motor and shows the result of iron loss distribution in the motor. Show more

DOI: 10.3233/JAE-2002-337

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 13, no. 1-4, pp. 245-250, 2002

Authors: Verdes, C.G. | Diaz, B.R. | Chantrell, R.W. | Thompson, S. | Stancu, Al.

Article Type: Research Article

Abstract: A Monte Carlo time and temperature dependent model was developed to simulate magnetization processes in fine ferromagnetic particle media. The model uses a combination between a time dependent Stoner-Wohlfarth model and a standard Metropolis algorithm to find the magnetization of single-domain particle systems. Both magnetostatic and exchange interactions are introduced explicitly. Variation of magnetic viscosity with interactions and temperature is studied. Results show that viscosity exhibits a maximum around coercive field. …The value of this maximum is closely related to the strength and the origin of interactions as well as to temperature. Dipolar interactions decrease the viscosity and broaden the viscosity vs. field curve, while exchange interactions lead to an increase in viscosity around coercive field. An increase in temperature up to the critical temperature for the superparamagnetic behavior leads to an increase in viscosity. Further increase of temperature produces a decrease in viscosity. Show more

DOI: 10.3233/JAE-2002-330

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 13, no. 1-4, pp. 251-256, 2002

Authors: Stancu, Alexandru | Stoleriu, Laurentiu | Cerchez, Mihai

Article Type: Research Article

Abstract: The interactions in particulate ferromagnetic media are generally described by magnetostatic interactions and exchange interactions. The Preisach type models describe the interactions by the use of an interaction distribution and a mean interaction field. It is usually considered that the mean interaction field is determined by the exchange interactions in the system, while the statistical interactions are determined by the magnetostatic interactions. This paper presents a micromagnetic analysis of the hypotheses used …in the Preisach models to describe the magnetic particulate system. Show more

DOI: 10.3233/JAE-2002-326

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 13, no. 1-4, pp. 257-262, 2002

Authors: Matsuoka, Taichi | Ohmata, Kenichiro

Article Type: Research Article

Abstract: A new type of magnetic damper using rare-earth magnets and a pinned displacement magnifying mechanism has been developed. The magnifying ratio and the resisting force characteristics of the damper and its effects of vibration suppression for a piping system were discussed experimentally, theoretically and numerically.

DOI: 10.3233/JAE-2002-321

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 13, no. 1-4, pp. 263-270, 2002

Authors: Verringer, Joseph | Nafalski, Andrew

Article Type: Research Article

Abstract: Recent developments in antenna design have led to fractal arrays -- recursively generated objects where successive dimensions are fractional. These arrays can provide frequency independent, multi-band characteristics that can be used to electromagnetically design an antenna that exhibits good properties over two widely separated frequencies for the purpose of satellite communications. The fractional design results are compared in the paper to simulation results in order to analyse the performance at the required …frequencies. Show more

DOI: 10.3233/JAE-2002-320

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 13, no. 1-4, pp. 271-276, 2002