Transcutaneous energy transmission systems that supply power to the ventricular assist device implanted in the human body have been studied. The magnetic field radiated from a transcutaneous transformer exceeds the limit set by the international standard CISPR 11. Therefore, we proposed a magnetic-field-reduction method using both 0° and 180° phase-shift transformers. In this study, we measured the magnetic field both in the case of using a single transcutaneous transformer (Type A) and in the case of using a couple of transcutaneous transformers (Type B). The receiving power of the load resistance was fixed at 14.4 W. As a result, the magnetic field became 59.0 dBµA/m in Type A, and 49.3 dBµA/m in Type B. Furthermore, the transmission efficiency was 57.2% in Type A and it was 45.2% in Type B when the distance between the couple of transcutaneous transformers was 30 cm. These results indicated the effectiveness of our method in magnetic-field reduction.

　High-hydrous gel phantom simulating the electrical properties of living body (relative permittivity, conductivity) is used, such as to evaluate the biological effect by the communication equipment. However, it is necessary to improve the electric properties of the phantoms in order to use in low frequency bands. In previous studies, the addition of carbon fiber to the phantom causes interfacial polarization and improves electrical properties in the low frequency band. Non-uniformity of the phantom, however, increases with the increase in carbon fiber amount, leading to a decrease in reproducibility. In this paper, we investigated to reduce the amount of inductive material and improve electrical properties in the low frequency band by adding activated carbon fiber with a large surface area instead of carbon fiber. As a result, although a large surface area was effective in the dielectric relaxation frequency, conductivity increased due to the conductivity of activated carbon fiber.

　The authors have been studying non-contact brakes using eddy current brake as the next generation for aircraft. This paper deals with three-phase alternating eddy current brakes using Cu composite discs. As a result, the braking torque using Cu composite discs is obtained 1.6 times compared to Cu disc. And then, it is found that there is a maximal braking torque by depending on material discs.

　The maximum magnetic flux leakage from a crack is obtained when the magnetic flux is distributed orthogonally towards the crack; thus, clear magnetic particle indications are formed, which enables accurate inspection of cracks via magnetic particle testing (MT). However, cracks may be overlooked in a complex 3D shape because a magnetizer often cannot be configured to the complex portion being inspected and the test object cannot be appropriately magnetized.

　In this study, the MT with a rotating magnetic field was executed for an H-shaped test object replicating a complex mechanical part, and the flaw detection performance in its complex shape portions was evaluated. Additionally, distributions of rotating magnetic flux density in a test object were analyzed with the finite element method. The analytical results and the actual magnetic particle testing results were compared.

　This paper investigates a vernier motor with a consequent pole rotor which reduces the permanent magnet volume and increases the productivity, compared with a surface permanent magnet (SPM) rotor. The consequent pole design may cause the reduction of the output torque and increase of the torque ripple due to the unbalanced flux density between the permanent magnet pole and consequent pole. The performance comparison between these designs is implemented by 2-D finite element analysis and measurements on a prototype.

　This paper describes the development of pressure distribution visualization device using relatively inexpensive and available materials such as PC keyboard boards and conductive rubber. If the device is cost-cut, it can be widely used in the field of rehabilitation and sports. Conductive rubber is inserted into a keyboard boards for a PC. The pressure can be estimated by measuring the resistance at each point. In this study, the basic performance of the prototype sensor was investigated by investigating changes in the thickness of the conductive rubber and the resulting changes in resistance from a quantitative perspective. As a result, proposed method can be useful to measure the pressure distribution under static conditions and sufficiently long time conditions.

　A planar motor with multiple movers has been developed to save the temporary storage space and automate packages loading and unloading in small warehouses. We propose a sensorless position estimation method for the multiple movers with permanent magnets and iron cores using each coil’s inductance under the movers. The inductances are measured in real-time using the current response, and each distance between the coil and the iron core is determined. The position measurement accuracy is evaluated using an experimental planar motor.

　In this paper, we propose a mathematical model for evaluating the performance of an onboard energy harvester. First, the static analysis results using the finite element method and the measurement results using a prototype are compared, and the parameters are supplemented as table data. In addition, the parameters necessary for a mathematical model are identified using a damping vibration. In order to easily evaluate the harvester, we propose a mathematical model that combines the results of using the finite element method with the identified parameters. Finally, a power generation experiment is conducted, and the experimental results are compared with the simulation results to discuss the validity of the proposed mathematical model.

　An AC magnetic suspension system operated differentially has been designed and developed to investigate the characteristics of AC magnetic suspension using magnetic resonance coupling. This device enables the floator to keep a constant position despite changing the parameters of the stator electromagnets by differential operation. A permanent magnet is incorporated in this system to minimize the required power supplied to the stator electromagnets. Magnetic suspension with a maximum gap of 3.4 mm or a minimum gap of 2.0 mm is achieved. Indirect damping is applied using VCM to make the system dynamically stable. The frequency response analyses the relation between the stiffness and the floating position and the effects of indirect damping on the suspension characteristics. The effect of the amplitude of the applied voltage and the applied frequency is estimated experimentally during the stable suspension in the differential operation.

　The Transcutaneous Energy Transmission Systems (TETS) can non-invasively transmit power to a totally-implantable artificial heart. One of the most important problem is the improvement of power transfer efficiency. We aimed to improve the power transfer efficiency by applying a class-E amplifier and reducing the switching loss. Moreover, the insertion mode of the capacitor for resonance (series resonance or parallel resonance) and the rectification mode are also important. We compared the power transfer efficiency and the frequency characteristics by the resonance circuit and the rectification mode by simulation.

　A number of automobiles have been fitted with electric motors and their inverters. In order to reduce the space of the motors, we propose a two-controllable-rotor motor which consist of 2 rotors and 1 stator. However, two-controllable-rotor motor is driven by a 6-phase inverter, and the space of its inverter is almost the same as 2 motors driven by 3-phase inverters. In this paper, in order to reduce the space of its inverter, we propose a two-controllable-rotor motor using a 5-phase inverter, and its operation principle is described.

　A transcutaneous energy transmission system (TETS) is one means of supplying power to a ventricular assist device. In the system developed in this study, to prevent necrosis, we set the distance between the transmitting and receiving coils to 2 cm, assuming that the receiving coil is embedded between the subcutaneous and muscle tissues. However, as the distance between the coils increases, the input impedance decreases because the electromagnetic coupling between the coils is reduced. Hence, a stable power supply cannot be provided, and coil heat is generated. To overcome this problem, in the proposed system, the power transmission is stabilized by a newly designed impedance converter, and coil heat is suppressed by changing the number of layers of the transmitting coil. As the result, a stable power supply can be provided, and a maximum transmission efficiency of 72.7 % is achieved. Furthermore, coil heat is reduced by 15.1 °C.

　Currently, there is a need for ultra-high-speed motors that exceed 100,000 rpm, such as turbochargers and compressors. Conventional motors have a problem that when they are driven in an ultra-high speed rotation region, frequency-dependent losses such as iron loss and eddy current loss become large. In contrast, the authors have proposed interior winding synchronous motor, and in this paper we compare the loss reduction effect with a conventional motor.

Transformers used in switching power supplies can be reduced in size by increasing the frequency. However, transformer loss increases with higher frequencies, which hinders higher efficiency. Therefore, transformer using interleaved winding is being considered. The authors consider the reduction of copper loss in the planar transformer for LLC resonant converter using interleaved winding. It was confirmed by analysis that the AC resistance was reduced by 55.4 % from 217.6 mΩ to 97.1 mΩ by applying interleaved winding. In addition, an interleaved planar transformer with a substrate pattern as a winding was manufactured, and through experiments, the efficiency of an LLC resonant converter using a transformer with an interleaved winding was measured, and the copper loss reduction effect of the transformer was demonstrated.

　High power wireless power transmission coils to be used for an electric vehicle (EV) and the automatic guided vehicle used in the plant (AGV) generally have the litz wire coil is used. The litz wire can reduce the high-frequency loss of the wireless power transmission coil. The smaller the number of strands, the easier it is to manufacture litz wires, but the higher the AC resistance. In addition, coil heat generation reduction and efficiency improvement are required. Therefore, the authors proposed a magnetic tape litz wire coil that reduces AC resistance and improves efficiency by winding magnetic tape around litz wire. The AC resistance was reduced from 73.9 to 64.9 mΩ by winding magnetic tape around the litz wire coil. The power transmission efficiency was improved from 88.4% to 88.9%. Heat generation from 1 kW power transmission was reduced from 64.3 ℃ to 58.1 ℃.

　A feed screw mechanism is used in various machines and robots. Mechanical screws such as ball and slide screws have various problems due to their mechanical frictions. In order to solve these problems, a magnetic screw which is one of contactless screws has been proposed. Nowadays, magnetic screw motors which a magnetic screw is integrated with a motor are proposed. However, these screw motors require permanent magnets in their mover, and the volume of the permanent magnets increases as the stroke increases. In this paper, in order to solve these problems, a magnetic screw motor whose permanent magnets are in its stator is proposed. The static characteristics of the proposed motor is investigated using 3-D finite element analysis.

　In recent years, electric motors having flat shape are desired in order to minimize system size as well as enhancing the efficiency. Therefore, axial gap motors (AGMs) have attracted significant attention because they can achieve higher torque density in flat shape than conventional radial gap motors. In general, AGMs employ Soft magnetic composite (SMC) for stator core since they have three dimensional magnetic paths. If AGMs employ SMC which has low iron loss characteristic, the efficiency can be improved. However, average torque is decreased because SMC basically has tradeoff relationship between iron loss characteristic and permeability. Hence, in this research, AGM having coreless rotor structure that torque performance is not easily affected by the permeability of SMC is proposed. In this paper, many virtual SMC materials which have different iron loss and permeability is considered for the proposed AGM. Finally, suitable SMC characteristic to enhance the efficiency over a wide operating range is revealed by three-dimensional finite element analysis (3D-FEA).

　The functions of sensing, control and communication in wireless sensor devices could be driven with minute electric power below mW level. In these devices, attention has been paid to minute electric power supply from environmental energy (light, heat, vibration, electromagnetic fields, etc.) instead of batteries. The power induced by leakage magnetic fields is a stable minute sources secured near electric power equipment. We proposed an environmental magnetic-field generator consisting of a solenoid coil and an prolate shell-type magnetic core to compress low-level magnetic fields below mT. The analytical equation of the electromotive force induced on the generator could be derived to characterize the performance. The validity of the equation was discussed by comparing the experimental results of the tested models with the calculated values by the expression. It was clarified that the shape of the generator was discussed and that a small power of mW level could be supplied.