Electrical technology has recently erupted into a wide area. Due to this knowledge explosion, it is difficult to take time to study individual items in detail. To obtain knowledge of the object item in less time, numeric simulation is a useful and effective method. We present in this paper, a simulation model and simulation scheme for a reactor using a ring core. Various simulations were performed, and the results are shown for demonstration.

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We defined an effective hysteresis model of two-dimensional magnetic properties for magnetic field analysis. Our hysteresis model is applicable to both alternating and rotating flux conditions. Moreover, we compared the calculated results with the measured ones and verified the accuracy of this model. We can calculate iron losses in the magnetic materials exactly. As a result, we show that the hysteresis model is generally applicable to two-dimensional magnetic properties of some kinds of magnetic materials.

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With the downsizing of switching power supplies in recent years, efforts have been exerted to develop smaller, more efficient power supply transformers with higher value added. In addition, the need to develop power-saving transformers has increased since the COP3 Framework Treaty on Climate Change Meeting held in Kyoto, Japan, in 1997. As a result, demand is growing for soft ferrite materials having higher flux density and lower loss. The current data on ferrite materials, however, do not reflect the operation conditions of switching power supplies. It is thus necessary to develop a new ferrite core evaluation method that enable prediction of power savings in power supply transformers in relation to ferrite material formulation, core shape, and winding mode. We report our current activities in material development and circuit design, with a view to establishing a new ferrite core evaluation method and to obtaining power-saving transformers with higher efficiency.

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Visualization of magnetic flux density using the CT (Computed Tomography) method was presented by using a reduced number of probe terminals. In this method, the sensor (CT probe) is composed of only the patterned coil plane, and can visualize two-dimensional magnetic flux density of a vertical component with the plane. The distributed data can be observed without scanning motion by use of a multi-layered CT probe. To obtain more effective measurement, we propose a new shape for the coil pattern with a switch function; this design permits display of an alternative magnetic flux density.

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This paper presents a new Eddy-Current Testing (ECT) probe configuration for inspection of printed-circuit boards (PCBs). The probe design had been based on a meander (exciting) coil and a pick up coil, which has solenoid structure. The paper includes the results of numerical calculation showing the magnetic flux distribution around defects, as well as experimental scanning results. It demonstrates that the probe can detect cracks on PCB conductors with high resolution.

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We used the Multi-Frequency Excitation Spectrogram (MFES) method for eddy current nondestructive testing of Inconel tubes. Inconel tubes have several kinds of cracks. Our measurements show that defects csn be evaluated using the spectrograms obtained from analysis of multi-frequency response of the eddy current sensor.

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We performed experimental and numerical studies on identification of opposite side defects in stainless sheet using Eddy Current Testing (ECT). Measurement and simulation with the 2-D boundary element method (BEM) we carried out to evaluate the sensor signals for opposite side defects in test specimens. We tried to overcome the outer skin effect of input voltage by using multiple frequencies in the numerical approach.

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We studied a detection and identification method for cracks and defects, using eddy current testing (ECT). To use impulse excitation, we performed numerical analysis by the boundary element method (BEM) with Laplace transforms. The shapes of cracks and defects are obtained directly from the BEM integral equation. We applied the singular value decomposition (SVD) and regularization method to the matrix for the unknown variables to obtain proper crack shapes.

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Eddy-current testing (ECT) is a non-destructive inspection method having various advantages, such as testing that involves both conduction and non-contact. One attractive application for ECT is inspection for etching defects in high-density printed-circuit boards (PCBs). To apply the ECT technique to PCBs, it is important not only to make a conformable probe but also to investigate the characteristics of signals using the probe to determine the shapes of defects. This paper describes characteristics of inspecting signals for shapes of defects. When resultant signals are expressed in two dimensions, we can clearly examine etching defects in PCBs.

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An ECT signal from a small reverse-side defect existing on a thick metallic plate is very small because of the long distance between the probe and the defect. To detect a minor reverse-side defect on a thick metallic plate, we therefore have to develop a new ECT probe with high sensitivity. We developed a new ECT probe with a gradio-magneto sensor, which consists of two MI elements and a CMOS electric drive circuit. The experimental results show that this new ECT probe using MI elements shows high sensitivity and stability.

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This paper deals with the impedance characteristics of an electromagnetic type rail joint gap sensor (RGS-SC) using probe coil for the ordinary railways. The sensor is able to detect a joint gap of rail by the change in impedance. The following results are obtained: (1) the impedance of the probe coil depends on the joint gap, the rail displacement, and the lift-off at constant frequency; (2) the impedances of the probe coil are 15.7 Ω and 16.4 Ω at joint gaps of 0 and 16 mm.

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Environmental magnetic noises change with time influence biomagnetic measurements. There are two types: artificial magnetic noises, and those caused by natural fields For example, the former are caused by the movement of objects composed of magnetic materials, such as cars or trains, elevators, and fan-pumps of air conditioners, on the other hand, the latter are caused by natural fields, such as volcanoes or solar wind. The magnitude of geomagnetism is about 10 ^-4 T, and that of movements of cars or trains, elevators, and fan-pumps of air conditioners are 10^-6 ∼ 10 ^-10 T. By contrast, the magnitude of magnetoencephalogram or magnetocardiogram is 10^-12 ∼ 10 ^-14 T. Although they are, very weak, environmental magnetic noises cannot be ignored we measured the temporal vertical component of geomagnetic changes with a SQUID (Superconducting Quantum Interference Device) magnetometer in the vicinity of the crater of the Mount Sakurajima volcano for about 40 days. taken, By comparing our data taken by SQUID with the data of by the magnetic observatory of the Japan Meteorological Agency, we confirmed that our data are convincing. The influence of magnetic fluctuation caused by volcanoes on biomagnetic measurement is also discussed.

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We tested the application of a magnetic ribbon to create a highly sensitive magnetic sensor. The sensor employs the impedance change in a magnetic ribbon when a radio frequency (rf) current is passed through it and an external magnetic field is applied. To achieve a highly sensitive magnetic sensor, we had to increase the impedance change. We examined a multilayered magnetic ribbon structure and interpreted the results by using an equivalent circuit of the impedances. The impedance change is enhanced by multiplying the number of ribbons in which rf currents flow in the same direction. The maximum variation rate in the impedances that are proportional to sensitivity was obtained with a double-layered structure.

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A common method for the measurement of dc-biased magnetic properties is the use of ring specimens. Although ring specimens are popular for measuring magnetic properties, it takes a long time to prepare the windings. It is therefore difficult to compare various kinds of specimens in a short period. This problem can be solved by using a single-sheet tester (SST). This paper presents an improved measurement system for dc-biased magnetic properties and some measured results for grain-oriented silicon steel sheets of different rolling direction.

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Thin-film inductors with micro-patterned CoNbZr films for impedance-matching elements in a 1-GHz-drive mobile communication handsets application have been demonstrated for the first time. Narrow slit trains along the easy axis direction and a square spiral coil control the ferromagnetic resonance frequency through changes in shape anisotropy energy and magnetostatic energy. Inductance increased by 18% compared with the air core inductor, while Q was almost the same.

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A novel high-frequency transformer using a fine-grain Mn-Zn ferrite has been proposed for transmission line use. The device consists of a fine-grain Mn-Zn ferrite core, polyimide film, copper planar spiral winding, and copper ground-plane, which operate as a distributed constant circuit. A quarter-wavelength transmission-line transformer with a large voltage-gain under higher impedance termination has been investigated, and it has been applied to a step-up transformer in a high-frequency inverter for a cold fluorescent lamp (CFL).

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A remote temperature sensing system was investigated for use, local such as inside the human body. The system was divided into a magnetic generating part, temperature sensing and temperature information generating part, and temperature information receiving part. A ferrite having a low Curie temperature was used in the temperature sensing part. To receive and transmit the temperature information effectively, LC resonance circuits were used in the system. The resonance frequency of 145 kHz to 220 kHz was varied in the range of 58°C to 66°C. From this experiment, we determined that temperature could be measured at the local site using this system.

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A new technique to control thermal convection that utilizes a gradient magnetic field has been introduced. First the magnetic field dependence of the pressure difference produced magnetically was examined. Next the changes of the thermal convection flow due to the position of the magnetic field center and to the experimental procedure were studied. Changes can be explained on the basis of a detailed analysis made by examination of the temperature distribution. Control of the thermal convection can therefore be made possible by control of magnetic field strength, position of the magnetic field center, and the experimental procedure, with no mechanically driven parts.

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The microwave absorption properties of BaZn₂Fe_16-x(Me_0.5Mn_0.5)_xO₂₇ (Me = Ti(0≤x≤4.0),Sn(0≤x≤2.5), Zr(0≤x≤2.0)) samples, prepared by a conventional ceramic technique, were studied. The W-type phase was obtained in samples of Me = Sn, Zr. The saturation magnetization (M_1,2), Curie temperature (T_c), and natural resonance frequency (f_r) of Me = Sn and Zr samples decreased with increasing (MeMn) content. The f_r values of the Me = Sn, Zr samples were shifted to 1.9 GHz (x = 2.5) and 2.1 GHz (x = 2.0), respectively. Better microwave absorption properties (R.L. ≤ -20 dB), however, were obtained for the Me = Sn samples, than for the Me = Zr samples. In the Me = Sn samples, the matching frequency (f_m) and matching thickness (d_m) were controlled in the range of 3.6 GHz to 16.5 GHz and 2.8 mm to 0.7 mm, respectively.

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This paper shows our experimental results for the heating characteristics of magnetic wood. We made a separate heating board and a multiple-ply heating board, to both of which were adhered magnetic wood and an excitation coil. The results showed that the multiple-ply heating board, which was combined with coated magnetic wood and a spiral coil, had superior heating characteristics and heating efficiency.

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We developed a human-size, open-structure, vertical cylindrical magnetic shield consisting of four shells. The inside diameters of the four shells are 0.67 m, 0.72 m, 0.82 m and 0.97 m, respectively. The lengths of the shells are 1.80 m, 2.20 m, 2.43 m and 2.75 m, respectively. The first shell is made of Permalloy (2.1 mm thick). Other three shells, made of amorphous ribbons (approximately 50 mm wide, approximately 22 μm thick), employ magnetic shaking. The second shell consists of four subdivided helical shells with internal space of about 10 mm. Each subdivided helical shell comprises of 12 layers, with the amorphous ribbons wound helically. The outer two shells have an axial structure, in which the ribbons are placed along the axial direction of the cylinder. The third shell has 26 layers and the fourth shell has 30 layers of the amorphous ribbons. The shielding factor measured at the center was approximately 100,000 for the transverse magnetic field and approximately 380 for the axial magnetic field, the amplitude of the magnetic field being in both cases 10,000 nT. The leakage field from the shaking coils at the center of the shield was below 1 nT permitting operation of highly sensitive SQUID magnetometers.

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We measured the magnetic shielding effectiveness of a cubic box constructed from grain-oriented silicon steel sheets. We also measured the effect of varying the box wall thickness on the shielding effectiveness. Experimental results were compared with theoretical expected results. We found that the shielding effectiveness for an alternating magnetic field in the 30 Hz to 5 kHz range was qualitatively explained by the permeability of materials and eddy currents in materials, and susceptible to the gap at the joint of the shielding materials.

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We propose a magnetic field compensation system that consists of a three-axis wideband magnetic sensor plus three coils and three current sources feeding current to compensate for external magnetic fields in biomagnetic measurements and the semiconductor manufacturing process. The new system shields against composite magnetic field noise of about 20 dB, ranging from dc to high frequency, including 50 Hz.

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Fingertip blood vessel pulsation (FTP) with a capillary blood vessel pressure of few milligrams was accurately detected using a CoSiB amorphous wire stress-impedance (SI) sensor which shows a giant strain-gauge factor of about 4000. The incisura in an FTP waveform was clearly observed for young subjects, whereas the incisura was only slightly evident in the FTP waveforms for older subjects. The FTP speed, and the change of FTP waveform before and after smoking, was measured in which the magnitude of FTP waveforms for some subjects rapidly decreased during smoking and gradually recovered to the original waveform after smoking. FTP sensing will be useful for diagnosis of the circulatory system and of the general state of health.

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Magnetophosphene, a light sensation perceived when a human head or visual system is exposed to an ELF magnetic field with enough intensity, is considered to be a sensation caused by activity of the stimulated retina. Estimation of the current density induced in the retina by a magnetic field is necessary for discussion of the phosphene. Electrophosphene is a similar light sensation perceived upon electrical stimulation to the eye. We calculated the current density distribution over all of the retina in an electrically stimulated human eye, using the finite element method. To discuss the threshold of current density that is required to cause retinal cell activity in a magnetically stimulated human eye, the density is compared with other results calculated under magnetic stimulation.

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This paper describes a study of the distribution of magnetic materials in statocysts of crawfish. We think that the magnetic materials extracted consisted mainly of iron, and the fact that iron is a major clement supports this conclusion. We measured particle size. The particle size range in this study was smaller than 140 μm. X-ray diffraction analysis of the magnetic material extracted from statocysts of crawfish supported the conclusion that the crawfish acquire soil particles.

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A new type of magnetic circuit for dental magnetic attachment is proposed for use on vital teeth. The circuit is called an “integrated structure.” Fe-Pt alloy was selected as the magnetic material, as it is superior in corrosion resistance in the hostile oral environment. Thin-film technology, such as photolithography and sputtering, was used to fabricate the structure. The experimental manufacture has proved that the new structure is effective in greatly reducing the height of magnetic attachment, thus enabling the attachment to be applied on vital teeth.

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This study focused on the physiological responses of somatosensory stimulation using magnetoencephalogram (MEG) and functional magnetic resonance imaging (fMRI). The time course of signal intensity of fMRI and the dipole moment of magnetic fields responses are compared. Although there are many studies related to somatosensory responses in EEG and MEG, only a few studies have been performed of somatosensory response in fMRI. To investigate the relationship between neural activity and the hemodynamic response or BOLD (blood oxygenation level dependent) effects, the effect of the stimulus intensity to the right thumb was investigated by fMRI and MEG techniques.

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The purpose of our study was to search for a specific parameter for diagnosis of acute ischemia and infarction. Magnetocardiograms (MCG) and electrocardiograms (ECG) of five rats with coronary artery occlusion were measured using a high resolution dc-SQUID (superconducting quantum interference device) gradiometer in a magnetically shielded room. In our system, the spatial resolution of the detecting magnetic field is higher than that of the typical system. The current distribution vectors were estimated from MCGs, while the heart vectors were estimated from ECGs. The amplitudes and angles of the current distribution vectors and the vector cardiograms were analyzed to determine the effect of coronary artery occlusion. Results show that the amplitudes of the current distribution vectors and the vector cardiograms at the ST segment and at the T wave were significantly increased by occlusion. The angle of only current distribution vectors at the T wave was significantly changed by occlusion. The angle of the current distribution vectors was a useful parameter for diagnosing of acute ischemia and infarction. Our system is a useful tool for basic studies of heart disease using small animals such as rats.

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We carried out a 3-D MCG vector measurement of the PR segment using a 3-D second-order gradiometer connected to 39 dc-SQUIDs, which can detect the magnetic field components perpendicular to the chest (Bz) and tangential to the chest (Bx, By). The MCG waveform showed a ramp pattern and bump pattern with a positive or negative slope for 40 ms before onset of the QRS wave, which corresponds to excitation of the His-Purkinje conduction system (HPS). The isofield contour maps of Bz showed a dipole pattern, and the isofield contour maps of Bx and By showed one extreme pattern. The source localization was done by a single equivalent current dipole (ECD) method for this time interval. It was shown that calculated ECD traced the HPS activation pathway.

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An algorithm based on the wavelet transform (WT) was developed to analyze the MCG signals recorded by a 3-D second-order gradiometer connected to three rf-SQUIDs. By using the band pass filter banks with different central frequencies designed with the WT algorithm, we performed MCG waveform analyses for a normal subject and a patient with myocardial infarction (MI). The high frequency components of the QRS complex related to the late potential (LP) lasting about 100 ms with more than few hundreds fT behind the offsets of the QRS complex were observable from a patient with MI. It is useful to use this WT algorithm for signal processing to 3-D MCG signals.

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Magnetocardiogram (MCG) measurement using high-Tc SQUID magnetometers is receiving attention as a diagnostic technique for observing the electrical activity of the heart because the instrument is easy to operate and the liquid nitrogen coolant is low in cost compared with the liquid helium used in conventional SQUID magnetometers. In this study, we carried out MCG measurement on ten normal subjects and four patients with inferior infarction, using a 16-channal high-Tc SQUID in a prefabricated, magnetically shielded room. Using isofield contour maps of QRS waves at different times, we were able to locate the signal sources and observe their different variance in the normal subjects and patients with inferior infarction. The result shows that the method using a high-Tc SQUID magnetometer will provide assistance in the diagnosis of cardiac diseases.

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Measurement of the magnetic fields of the lung, called magnetopneumography, provides a good tool for those engaged in lung research. The distribution of accumulated particles in the lung, however, is not accurately reflected by a measurement value for magnetic flux density alone. Actually, it is necessary to determine the distribution of particles in the lung quantitatively to be able to apply results for clinical use. To estimate the distribution and amount of magnetic dipoles, we used a spatial filter to reduce noise in the measurement values. An analytical result by the least squares method is provided that uses a method for removing the noise included in the measurement values with a spatial filter. This analysis method is called magnetic noise elimination.

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Little electric power, thin cellular phones are gaining remarkable popularity. Most recent cellular phones have a vibration function generated by a rotary vibration motor to notify the user of arrival of a message. We developed a little electric power, thin Linear Oscillatory Actuator (LOA). Its vibration acceleration is larger than that of rotary vibration motors. This paper describes: (1) the structure and operating principle of the LOA for cellular phones, (2) effect of a center yoke for increasing thrust force of the LOA, (3) influence of a center yoke on the LOA electric power for cellular phones, and (4) comparison between the LOA and rotary vibration motor.

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The electrical and mechanical time constants of the linear dc motor (LDM) are required to be small so as to achieve a high-speed response. This paper describes a design method of the magnetic circuit and the electrical and mechanical time constants on a moving-magnet-type LDM. The following results are obtained:
(1) Design a high-speed-response moving magnet type LDM using the expressions of the electrical and mechanical time constants.
(2) In the LDM designed using this approach mechanical time constant is 1.9 ms and erectrical time constant is 5.4 ms. Moreover the calculation by FEM mechanical time constant is 2.0 ms and erectrical time constant is 4.6 ms, and the differences with a pemeance method are 5 % and 17 % grade, respectively. Therefore, this design approach using the pemeance method is useful as means to calculate characteristics of LDM as compared with the calculation approaches, such as FEM, though it is simple.

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We have fabricated and developed a novel flux-concentration-type linear induction motor (FCLIM) utilizing the effect of the flux concentration by eddy currents. In the developed FCLIM, leakage flux between the yokes is reduced and more flux is concentrated into the air gap. It is evident from the results calculated using equivalent circuit parameters and from the experimental results that the FCLIM's performance is superior to that of a normal tubular linear induction motor (LIM).

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An X-Y Linear Induction motor (X-Y LIM) is a structure having two windings in the horizontal -X and Y- axes directions. One-direction thrust is created by exciting one winding, and a two-dimensional drive becomes possible by exciting two windings at the same time. We modeled only one pole of an X-Y LIM having a three-phase, six-pole structure, and used a three-dimensional finite element analysis method that ignored end effect and the influence of winding overhang. The following characteristics were examined to obtain guidelines for future designs: (1) flux density with respect to slot depth; (2) flux density with respect to the primary current; and (3) the relation-ship between the air gap and the thrust.

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We have reported various characteristics of systems using an X-Y LIM (X-Y Linear Induction Motor) for non-contact transport. Until now, transport, required coincidence of the center of gravity of the bogie-truck and the center of that truck. The center of gravity on the bogie-truck, however, is not always located at the center of the truck because of the load shape, weight, and so forth. We investigated the following aspects of fundamental switching performance of the system: (1) differences in switching caused by shifts in the center of gravity of the bogie-truck; (2) the relationship between starting thrust and switching angle for shifts in the center-of-gravity position on the bogie-truck; and (3) the relationship between starting thrust and rotational angle for center-of-gravity position shifts.

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We studied linear compensation and precision control of nonlinear hysteric piezoelectric actuators using a highly magnetostrictive amorphous FeCoSiB film pattern as a strain sensor. The elements had a hybrid structure in which thin silicon substrates with the magnetostrictive films, the strain sensitivity of which was improved by annealing with bias stress, were bonded on PZT piezoelectric substrates. The magnetostrictive film as a strain sensor detects the deflection of the actuator, and a voltage signal from the strain sensor related to a deflection of the actuator is used for control of the actuator. The application of the actuator for control of the head-disk contact properties was demonstrated.

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Performance of a new electromagnetic friction-drive micro-motor has been improved. The motor uses a magnet rotor with inclined legs and a driving coil, in which an electromagnetic vibration is converted into a rotary movement through the friction of the legs. To increase the torque by increasing the attractive force between the stator and the rotor, we used a coil with a ferrite core and a modified geometry. As a result, the maximum torque reached to 0.35 mNm, which is 27 times that of our previous result.

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High-speed rotation of amorphous wire in an ac longitudinal field was investigated in relation to magnetostrictive vibration for Fe, Fe-Co, and Co based wires. It was found that high-magnetostriction Fe and Fe-Co based wires rotate around the wire axis, but low-magnetostriction Co based wire does not, and that the rotational speed is a linear function of magnetomechanical resonance freqency. It seems from these observations that the rotation of amorphous wire around its axis originates from the magnetostrictive vibration.

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We present magnetic field analysis using the E&S model and calculations of iron loss for a three-phase induction motor model core. The E&S model can express two-dimensional magnetic properties. This model shows better properties than does the conventional method, and this model can express both alternating and rotating flux conditions. It therefore can be said that using this model for magnetic field analysis is very useful, permitting evaluation of iron loss distribution.

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A novel method for non-contact detection of an I₂ signal is presented using an MI sensor head inside a hole drilled through the shaft of a general-purpose induction motor (IM). An almost pure I₂ signal at the slip frequency is stably detected. The secondary-current, feedback-type torque control system is constructed using a general-purpose V/f inverter controlled by a PC system. Accurate control continues even after long operation that increases the temperature in the IM. An improvement in response speed is obtained using the state-feedback technique.

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We have already proposed a new type of parametric motor using a laminated iron core, and have also shown that the output and efficiency of the trial motor are comparable to conventional single-phase capacitive motors. In this paper, we discuss the performance characteristics and stability of the parametric oscillation of a laminated-core parametric motor using an asymmetric stator.

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Switched reluctance motors (SRM) have several desirable features, including simple construction, high reliability, and low cost. The operating characteristics of the SRM depend on the excitation conditions, such as the phase angle and pulse width of the excitation voltage applied to the motor winding. For the optimum design, it is necessary to clarify the quantitative relationships between the excitation conditions and the operating characteristics. We conducted experiments to determine the torque-speed characteristics and efficiency of the 8/6 four-phase SRM for various phase angle of the excitation voltage. Results showed that the trial SRM has an efficiency of more than 80% over a wide operating range.

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Camcorders would be more compact, lighter, and lower-priced if their drive motors were built into their lens barrels. We propose a new direct-drive motor built into a lens barrel. This motor has a three-phase set of armature windings. Only two phases are excited by a rectangular source, and the other phase is not excited. This paper presents a new drive method, called “three-phase on mode by a sinusoidal source,” in which all three phases are excited by a sinusoidal source to get a smooth axial shift of a rotor. We confirmed that the rotor of the motor shifted smoothly in an axial direction, using the new drive method. Calculated rotor displacements and times agree well with measured values. Torques do not depend on frequency and are constant below 20 Hz. The principles for the new drive method for the motor were verified.

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We have investigated various prototype magnetic gears in which the pinion and gear are separated by maintaining a gap. Such gears have the merit of eliminating contact, and they do not need lubrication, both of which virtues are unobtainable with ordinary gears. The present study of magnetic gears is intended to establish operating principles for gears using permanent magnets or electromagnets.
In this report, I present the prototype development and performance characteristics of a multispeed, single-plane magnetic gear suitable for practical use.
Results show that it is reasonable to enlarge the intersecting zone of contact area in the case of kinematic motion or to enlarge the main contact zone for heavy load carrying.

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A permanent magnet bearing system has been fabricated in our laboratory that utilizes the repulsive forces operating between the stator and rotor permanent magnets for the levitation without any radial control. Usually a magnetic bearing system characteristically has constant stiffness in the radial direction and is soft at steady position. Therefore, it is required to determine the rotor vibration conditions at high rotational speed. This paper discusses the attenuation of vibration for axial and radial disturbances in this system. The rotor runs through the critical speed effectively owing to the soft stiffness.

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