A high temperature superconducting (HTS) cable has been researched in many countries. We have studied an HTS tri-axial cable that is composed of three concentric layers. A tri-axial cable is more advantageous than a triad co-axial cable that is composed of three cores in one cryostat. Since conventional tri-axial cables had not realized three-phase equilibrium, we proposed a tri-axial cable composed of two longitudinal sections with different twist pitches. However, it is too difficult to realize the designed twist pitches in manufacture process. Therefore, we investigated the influence of fabrication errors in the twist pitches on electromagnetic properties of a tri-axial cable. In this paper, we evaluated the combination of the twist pitches that realize the maximum imbalanced ratio. Then, we considered the worst error in twist pitches and how long the tri-axial cable can transmit electricity safely.
This paper proposes two types of novel magnetic-geared motors which are superior to conventional magnetic-geared motors in terms of torque characteristics. The concept and operational principle of the proposed magnetic-geared motors are described. Finally, the proposed magnetic-geared motors are compared with the conventional magnetic-geared motors using the N-T curve.
Achieving a high efficiency in rotating machines is especially important in terms of saving energy. It is well known that the efficiency of a rotating machine such as the induction motor is not 100%. The manufacturing process of a rotating machine increases iron loss. This problem is called the building factor problem. The cause of this problem is a residual tensile stress and a residual compressive stress in the stator core caused by the manufacturing process. It is well known that the circumferential iron loss distribution of the stator core was changed by a residual tensile and compressive stress in the stator core. In addition, they also influence the axial iron loss distribution. Therefore, it is necessary to know their influences on the axial iron loss distribution. In this paper, iron loss and other magnetic properties of an actual stator core of the complex configuration was evaluated by using a small excitation inner core under the external compressive force. The results indicate that magnetic properties such as iron loss (Wi) of the laminated actual stator core clearly depend on the axial position, the circumferential position and the external stress.
In recent years, Ultra wideband (UWB) technology has been drawing attention as a promising technology in order to materialize ubiquitous network. Third-Generation (3G) smart phones which employ the UWB technology have been hot. In this paper, a UWB antenna built into the smart phone was investigated. As a result, the antenna with the VSWR less than 2.1 at both 3G and UWB frequency bands, which was enough in practical use, was designed and developed.
The crystal grain shape of GO sheet is considered by three-dimensional polycrystalline magnetic field analysis in which grains grown horizontally and grains grown vertically are compared. Because the grains grown vertically have more grains grown nearly parallel to the direction of the magnetic field than the other ones, they have uniform magnetic flux density distribution and then small iron loss. Therefore, the grains grown vertically are preferable to the grains grown horizontally in order to reduce the iron loss.
The measurements of the effective coercivity (Hc) of magnets are very difficult to determine as a function of the internal fields in samples with arbitrary shapes. We tried to obtain the exact coercive force, M-H curve in high pulsed magnetic fields up to 20T with an induction method using a triple-fold pick-up coil. The values of Hc were found over-estimated more than 20% for the Nd-Fe-B magnets in comparison with those announced by the company, caused physically by the leakage fields in between the sample and probe. The flux distributions were well simulated with the errors using the software of JMAG. The nature of magnetically isotropic microstructure of the raw material in the sintered Nd-Fe-B samples was also clarified in this study.
This paper reports a novel system that real-timely detects the respiration and the heartbeat during sleep for the purpose of early diagnosis of Sleep Apnea Syndromes. Real-time discrimination of the signal components related to the respiration and the heartbeat was realized using the Independent Component Analysis from the observed signals of PVDF films, which are placed on the bed under the bed sheet. Body movement is taken into consideration in order to prevent the system from divergence and to improve the discrimination accuracy. Efficacy of the system is testified through experiments.
Phantoms that mimic the electrical properties of the human body are widely used for the safety assessment of medical equipment, etc.Although a high hydrous gel phantom is useful in the high-frequency band, there is no phantom that can mimic the living human body in the low-frequency band. A living body's relative permittivity cannot be acquired by adjustment of the quantity of material in a frequency band of 10 MHz or less. Therefore, a carbon microcoil (CMC) was added to the conventional phantom in this study, and the relative permittivity in the low-frequency band improved.
A magnetically suspended total artificial heart has been developed with a single magnetically suspended motor. The device has double pumps to replace the function of the left and right ventricles. A stator which has both of a magnetic bearing core and a motor stator core is set at center of the device. The left and right pump impellers are connected with a rod through the center hall of the stator core. Attractive forces produced by the magnetic bearing and the motor are made balance to suspend the rotating impellers. Flow difference between the left and the right pump is regulated by changing the amount of the secondary flow through blood gap between impeller top edge and pump casing by shifting the impeller position axially. Flow rate of the left pump is changed 4.1∼6.7 L/min, flow rate of the right pump is changed 6.5∼7.4 L/min when axial position of the impeller is shifted by ±0.2 mm.
In this paper, a new highly efficient wireless communication link around human body using magnetic resonance coupling was proposed and investigated. The communication between wearable devices located on forearm and upper arm, like a wristwatch or armband, is assumed as a model for body area communication. The transmission characteristics S21, between transmitting and receiving antenna which is put on forearm and upper arm, respectively, like a wristwatch or armband, were analyzed and measured. As a result, the transmission characteristics S21 showed the maximum value of -3 dB, and was excellent compared with that of conventional body area communication using the electrodes in contact with the body. Moreover, the SAR of the body was less than a three-hundredth compared with the safety limit of 2 W/kg. Therefore, we confirmed that the wireless communication link using magnetic resonance coupling is useful for body area communication.
Creep-fatigue damage for welded specimens of austenitic stainless steel SUS316FR and high-chromium steel Mod.9Cr-1Mo was investigated by magnetic characterization techniques such as vibrating sample magnetometry and magnetic force microscopy. In SUS316FR at weld metal region remanent magnetic flux density decreased as creep-fatigue strain increased and it resulted from the decrease of δ-ferrite at weld metal region. In Mod.9Cr-1Mo steel at weld metal region permeability increased and micro-vickers hardness decreased as creep-fatigue damage increased and it resulted from magnetic domain structures change during creep-fatigue. It was found that the creep-fatigue damage for these energy structural materials was related to magnetic characteristics change which caused by micro-magnetic structure.
This paper proposes a novel rotary vernier actuator which can rotate bidirectionally according to the principle of a linear vernier motor. It is clarified by using 3-D FEM that the cause of the cogging torque and torque ripple is the permeance between the stator and mover and the end effect due to the arc-shaped stator. It is also discussed how the skewed mover or the arrangement of two blocks of the stator can reduce these ripples.
In daily life, we often use earphone to listen sound and music. However kanal type earphone like earplug shape shuts off the sound of surroundings, thus, is not preferable to use in jogging or driving. Bone conductive speaker is alternative to hear sound from surroundings and player simultaneously. However conventional ones based on piezoelectric material or voice coil are large size, difficult to equip, and amplifier necessary due to the low output force. Here, we propose functional earphone using magnetostrictive vibrator. The device consists of magnetostrictive rod (Galfenol) and magnetic yoke constructing unimorph structure, winding coil, bias magnet and vibration plate. The ring shape vibrator with hole to pass air-conductive sound is easy to equip on ear hole and can generate sufficient sound without additional amplifier. In this study, we fabricate several prototypes to evaluate static and dynamic characteristics to verify the principle and advantages.
When a robot system is developed by only normal motors that rotate around an axis, the necessary number of motors is the same as that of joints resulting in large and complicated system. On the other hand, spherical motors will realize a small and simple mechanism because they can rotate in various directions. The authors developed a spherical motor in which a permanent magnet is placed on each apex of a truncated octahedron for the rotor and an electro-magnet is place on either the apex or the middle point of two apexes of a regular dodecahedron for the stator. The spherical motor has two kinds of rotation axes and rotates totally around six axes. This study proposes a technique to change rotation axis and develops a control electronic circuit to generate PWM signals depending on the axis and direction of rotation. The circuit is composed of several micro-controllers applying CAN technique for data communication. The results of experiments to change rotation axis show that the proposed a technique work successfully.
The effect of a series connection on micropumps using oscillating elastic films has been investigated. The moving part of the micropump is composed of a NdFeB magnet and a polyimide film. When an alternating magnetic field is applied, the magnet oscillates rotationally due to magnetic torque, which causes the film to fan the fluid and induce the flow. At first the basic pumping properties of the single and serially connected micropumps were evaluated. The output pressure was proportional to the number of the pumps in series. Based on this result, a novel liquid cooling system for portable electronic equipment such as a laptop computer has been fabricated and tested. The prototype including multiple micropumps serially connected in a cooling pipe has successfully demonstrated good cooling performance.
A bearingless motor is characterized by integration of an electrical motor and a magnetic bearing. Electromagnetic force generated by the magnetic bearing function can realize magnetic suspension of a rotor shaft without mechanical contacts. Principal authors have been proposing a non-contact canned motor pump using the bearingless motor. This pump has no expendable parts, such as shaft seals, mechanical bearings and lubricant. Therefore, it can realize next advantages; 1. clean liquid sending. 2. maintenance free 3. longer operating life. 4. high chemical resistance. The previous paper has proposed novel structure which can generate high output and high suspension force compared with conventional structure. A prototype bearingless canned motor pump with the proposed high power structure is produced, and characteristics of suspension force and torque is tested in the prototype machine. This paper introduces the experimental results of the prototype machine with the proposed high power structure in detail.
The goal of this study is to develop a device which is used to both energy storage and wireless power transfer for ultra-low energy applications. It is a flywheel-like device with new concepts. This device consists of a rotating module and magnetic energy harvesting module. The rotating module is a rotating mechanical device that is used to store not only rotating energy but also magnetic energy. To make it simple and low costs, we use a geared-shape magnetic material between two antiparallel magnets. The magnetic energy harvesting module is an “on demand” power receiver device that is used to convert magnetic energy to electric energy. This paper focuses on this wireless power transmission performance. We consider the magnetic core shape for the magnetic energy harvesting module, and evaluate the harvesting power and its efficiency as a function of distance between two modules.
Eddy-current (EC) displacement sensors are used in a device for measuring the shaft vibration of turbines. When only the 1mpedance/voltage (Z/V) converter breaks down, it is necessary to recover as soon as possible. Therefore, identification method type of sensor probe and displacement and development Z/V converter which is suitable for each probe sensor are required. In this paper, we propose method for identifying type of sensor probe and displacement while operating a power plant with and adjusting sensitivity of six types of sensor probes. As a result, identifying type of sensor probe and displacement by measuring oscillation voltage, oscillation frequency and DC resistance of sensor probe is possible. In addition, sensitivity that meets the API standards is possible with present adjustment sensitivity method even if estimation error of displacement.
This paper deals with a new fabricated equipment to investigate a possibility of noncontact power feeding under a high speed relative motion with. First, we designed magnetic resonant type transmitting and receiving antennas and confirmed the transmission efficiency of paired antennas. Moreover, we clarified the effects of adjacent transmitting antennas on transmission efficiency from both static experiment and calculation with equivalent circuit. In the paper, we have demonstrated that the transmitting efficiency does not fall down even when the rotor having eight transmission antennas rotates up to a peripheral velocity of 72 km/h.
We investigate a L-shaped vibrational energy harvesting device using magnetostrictive material (Galfenol) for high output generation and efficiency. Galfenol is ductile magnetostrictive material with large inverse magnetostrictive effect. The device features higher output and efficiency compared with our conventional type. The device is a pair of L-shaped parallel beams consisting of Galfenol plate wound coil and stainless yoke and bias magnet. When a bending force is applied at the tip of the beam, bending moment is exerted on the Galfenol plate which yields uniform axial stress inside plate. Due to the inverse magnetostrictive effect, this stress causes flux change which time variation generates voltage on the wound coils. Prototype was verified maximum instantaneous power of 11.4W and maximum power of 0.1 J at a free vibration of frequency of 60 Hz. The output energy was increased from 20 to 30% compared with conventional type. The energy conversion efficiency more than 30% was observed.
A tuned liquid column damper (TLCD)—devised for vibration mitigation of high structures—is a passive damper categorized as a dynamic absorber. A magnetic fluid is a smart, colloidal, and strongly magnetizable fluid, and is composed of a base liquid, ferromagnetic particles, and a chemically adsorbed surfactant. Using a magnetic fluid as the working fluid of a TLCD can improve and change the TLCD into a novel semiactive damper called a tuned liquid column damper with a magnetic fluid (MF-TLCD). The natural frequency of a MF-TLCD can be changed by applying magnetic field. This novel damper can be used as an effective vibration suppression mechanism for building structures. In this study, we present the equation of motion of a MF-TLCD, and solved it numerically using a 4th-order Runge-Kutta method. Using the numerical results, we demonstrate the frequency responses of a MF-TLCD and the effect of the magnetic field on the natural frequency of a MF-TLCD. In addition, we compare numerical results with experimental results, and show that they are coincident qualitatively.
An eddy current sensors have various uses, for example metal detection and determination, nondestructive inspection, and position detection. However, there are few studies which show the influence of a conductor on the impedance of a detector coil using a theoretical formula. This paper shows the simplified calculation method on impedance of a planar coil that can be found from an equivalent circuit by considering that a conductor plate is one turn of coil which form changes according to displacement. The impedance corresponding to the overlap length of a conductor plate was calculated about the planar rectangular coil and the planar triangular coil. The calculated value was compared with the measured value and the calculated value of finite element method. The calculated value of impedance of rectangular coil and triangular coil agreed with the measured value within an error of ± 5.98%. Mutual inductance between the planar coil and conductor plate was calculated from the area ratio of planar coil and overlap.
This study intends to assess elastic and plastic deformation of carbon steel (SS400) and austenitic stainless steel (SUS304) by measuring magnetic flux leakage near a specimen surface using a hall sensor with high sensitivity and high spatial resolution. We measure the tangential components of Magnetic Flux Leakage near the specimen surface under residual magnetization condition. In the results, it is confirmed the MFL signal shows characteristic trend with respect to the elastic and plastic deformation. Furthermore, it is shown that the distribution of plastic deformation and residual stress can be estimated by MFL distribution.
Ferromagnetic materials have the interaction between mechanical and magnetic fields, which is called magnetoelastic coupling. Also it is known that magnetic properties of ferromagnetic materials depend on plastic deformation. There are various kinds of Non-Destructive Testing (NDT) based on these phenomena for fatigue estimation. We propose a new analytical method of magnetic hysteresis curve, in which the saturation magnetic hysteresis curve is decomposed to neutral magnetization curve and hysteresis gap curve. Each of the curves is expanded into power series, and its coefficients are extracted as parameters for the estimation. To verify this method, saturation magnetic hysteresis curves of STS410 steel with various fatigue degrees are measured. The method is found to be promise for the fatigue estimation.
An analysis of a symmetric wireless power transfer circuit is presented for a frequency control method to obtain maximum load power. Wireless power transfer for small medical devices such as artificial cardiac pacemakers, cochlear implants, and Holter monitors are very important. The power consumption can be reduced with simplification of the power control circuit in the devices. We have proposed a method to obtain a maximum load power in a symmetric magnetic resonance wireless power transfer system by a frequency control using the measurement of the current on the transmitter side.
Traditional ways of using plasma for medical application are blood coagulation and sterilization and etc. Recently, plasma has been used for medical treatment at Drexel University in USA. In their study, sever burn has been treated by using plasma irradiation. If plasma medicine is established, it is possible to start new regenerative medicine. They study therapies by using plasma irradiation, but the examination of safety for living body is not enough. Therefore, in this study, I investigate the effect of plasma irradiation treatment for the living body. The first step of my study, I report the changing of the Cardiovascular System by plasma inhalation.
Recently, the permanent magnet type linear synchronous motor (PM-LSM) is used as a driving source in transportation systems. In order to apply to the source of the power of the long-distance conveyance equipment, our laboratory have proposed an intermittent stator PM-LSM (ISPM-LSM). However, ISPM-LSM produces the velocity ripple due to an outlet edge of the stator. The sequence of the section changing method is changed in this paper. This suppresses the velocity ripple. The verification is performed using both of the simulation and experimental device.
Recently, the inspection of position and depth of reinforcing steel bar in a reinforced concrete structure is important. An electromagnetic induction method and an electromagnetic radiation radar method are used for inspection techniques of nondestructive. But, a general inspection technique also has the problem. Other techniques are actively researched now. Authors previously proposed a method of estimating position, depth and diameter of a single reinforcing steel bar by using the pulse-magnetization. In most cases reinforcing steel bars are usually found in more than one the reinforcing steel bars. Authors examined the method estimating the positions of reinforcing steel bars in more than one the reinforcing steel bars. The magnetization characteristic of the reinforcing steel bar was examined, Authors confirmed about the technique for estimating of the position of the reinforcing steel bar through the basic experiments and simulations, and report.
The Ministry of Economy, Trade and Industry of Japan reported that about 53% or more of the total electric power generated in Japan was consuming in motors. There are several kinds of motors, however induction motors are most popularly utilizing in factories. Therefore reducing losses and improving efficiency of the common induction motors are effective for saving energy. In this paper we focused on a synchronous induction motor (IM/PM hybrid motor), which permanent magnets are embedded in the induction machine's rotor. This machine can improve the staring characteristic in comparison with a synchronous permanent magnet motor and torque characteristic and efficiency at synchronous operation in comparison with an induction motor. The torque characteristic of IM/PM hybrid motors are numerically analyzed with the finite element method and compared with that of IM. The results show that the arrangement of the permanent magnets is very important to improve whole torque characteristics.
The purpose of this study is to develop a direct-drive, high-efficiency, small-sized axial gap microhydro-electric generator whose diameter is around 300 mm - 500 mm and output power is 1 kW at 20 rpm. In this designing, we have tried to use magnetic material attached flux concentration permanent magnet (MFCPM) arrangement in order to feed larger magnetic flux. Also the magnetic flux is enhanced by inserting a piece of electrical steel sheets in the MFCPM arrangement. The structure of the MFCPM arrangement, the combination of the segmented permanent magnets and the electrical steel sheets is optimized in cut-and-try optimizations by using the three-dimensional finite element method. The calculated result is compared with that of the surface permanent magnet (SPM) type axial gap generator with a combination of 36 poles - 54 slots.
Amorphos metal has very low iron loss and is expected to improve the efficiency of electrical machine such as motors. In general, amorphos cores are thought to be more superior in high speed motors because iron loss increases with frequency and amorphous metal's low iron loss properties are effective in high frequency region. In this report, however, we studied applicability of amorphous cores for low speed axial gap motors and found that the superiority over electric steel 35A300 existed even in low speed motors. We designed the double rotor axial gap motor which the rated output is 750r/min and 2.0N·m and the amorphous core motor shows 3% efficiency superiority over magnetic steel core motor. Also we found that the difference of efficiency gets wider in low torque output.
We previously reported that an ac Ampere type maglev conveyance system can maintain levitation height of an aluminum (Al) plate at a constant level while suppressing heat loss in the plate. In this paper, we focus on the cogging force which the proposed Ampere type maglev necessarily creates when the system stably levitates the Al plate. In comparison with a conventional ac induction type maglev system, we experimentally found that the Ampere type maglev created less cogging force in the conveyance direction. We also verified that the phenomenon contributed to energy saving at the starting to convey the Al plate.
Distance sensors using electromagnetic field have advantages of simply configuration and strongly to environment change. However, these sensors are short operating distance because the electromagnetic energy is strongly attenuation depending on the distance. Therefore, a distance sensor using magnetic resonant coupling was proposed. In this study, a distance sensor using magnetic resonant coupling with a switching function of a matching circuit is proposed for further long distance detection. A detection range of the distance sensor is examined from measurement and calculation. As a result, it is clarified that the distance sensor can be detected a ratio of a length l between transmitting and receiving coils to inner diameter d of coil l/d = 0 to 1.5 by switching with or without matching.
In this paper, we propose an energy storage circuits for magnetic energy harvesting. We successfully harvested 104 mW from applied magnetic field of 90 μT at 60 Hz. This magnetic field is smaller than the value that ICNIRP2010 guideline provided. In order to use effectively the harvested energy, we consider energy storage circuits. Because an increase in an output voltage produced an increase in the storage energy, we use Cockcroft-Walton circuit for transform AC to DC voltage and step up voltage. Our proposed storage circuit consists of Cockcroft-Walton circuit, capacitor, and constant voltage circuit. It was found that the storage energy was proportional to the square of number of Cockcroft-Walton circuit steps. From experiments, we successfully demonstrate that our energy harvesting device can provide an energy of 1 J for magnetic flux density of 5.43 μT.
This paper presents development of an industrial motor with an amorphous winding core for large capacity applications. The motor is developed for establishing proper motor designs to apply amorphous cores to large capacity motors. The motor design and the test results of a trial motor are discussed in this paper. In this research, we targeted the development of a motor which has IE4 efficiency with half the size of the previous motor. It was confirmed by the tests of the trial motor that the development targets can be surpassed by the design of obtaining higher output at high efficiency and the design of decreasing iron loss and copper loss. Comparing of the current motors for industrial motor, this motor obtained a much higher efficiency, which demonstrated the low loss amorphous core stator can contribute to high efficiency.
The cancer death toll of the digestive organs increases every year in japan. Now, the capsule endoscope is paid to attention as an image diagnosis device. However, the capsule endoscope is not equipped with locomotive system. So, research institutions develops locomotive system for the capsule endoscope. In this paper, the result of simulation that the power which is needed for this system is shown. And we described the result of animal experiment for checking the validity of this system.