Gen-ya Hattori - Academia.edu (original) (raw)
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Papers by Gen-ya Hattori
IEEE Transactions on Magnetics, 2015
The objective of this study is to provide suitable approximations of effective permeability for m... more The objective of this study is to provide suitable approximations of effective permeability for magnetic concentration cores. This core has dumbbell-shape, so that the magnetic flux is concentrated to the coil winding part of the core. It is well known that the demagnetizing factor strongly depends on the core shape which defines the effective permeability. Although several researchers have already proposed an approximation for a dumbbell-shaped core, it cannot take into account the flange part length. In this paper, a novel approximation for dumbbell-shaped core is proposed. It is based on the demagnetizing factor and correction terms related to the aspect ratio of both the flange and coil winding part. From experimental results, the validity of the approximation is confirmed.
EPJ Web of Conferences, 2013
This paper presents magnetic flux concentration methods for magnetic energy harvesting module. Th... more This paper presents magnetic flux concentration methods for magnetic energy harvesting module. The purpose of this study is to harvest 1 mW energy with a Brooks coil 2 cm in diameter from environmental magnetic field at 60 Hz. Because the harvesting power is proportional to the square of the magnetic flux density, we consider the use of a magnetic flux concentration coil and a magnetic core. The magnetic flux concentration coil consists of an aircore Brooks coil and a resonant capacitor. When a uniform magnetic field crossed the coil, the magnetic flux distribution around the coil was changed. It is found that the magnetic field in an area is concentrated larger than 20 times compared with the uniform magnetic field. Compared with the aircore coil, our designed magnetic core makes the harvested energy tenfold. According to ICNIRP2010 guideline, the acceptable level of magnetic field is 0.2 mT in the frequency range between 25 Hz and 400 Hz. Without the two magnetic flux concentration methods, the corresponding energy is limited to 1 µW. In contrast, our experimental results successfully demonstrate energy harvesting of 1 mW from a magnetic field of 0.03 mT at 60 Hz.
Smart Sensors, Measurement and Instrumentation, 2013
We propose the design of AC–DC converter for a magnetic energy harvesting device. When this devic... more We propose the design of AC–DC converter for a magnetic energy harvesting device. When this device is used as an energy source for wireless sensor applications, the DC output voltage should be larger than 1.5 V. First of all, we investigate the efficiency of conventional circuit whose has power conditioning module varied input power. It is found that efficiency of this module is at most about thirty percent. In the next place, we investigate the basic properties of an AC–DC converter with a Cockcroft-Walton circuit. Experimental results reveal that the optimum conditions are related with the number of steps, input voltage, input resistance, and dummy load. From a magnetic field of 675 nT at 60 Hz, the new magnetic energy harvesting device used Cockcroft-Walton circuit can provide a DC output voltage of 1.5 V. Compared with the previous device installed conventional power conditioning module we developed, the required magnetic field is as low as 1/400 in amplitude. In contrast, the measured efficiency of the device is better than 80 % when the magnetic field is larger than 20 μT.
IEEE Transactions on Magnetics, 2015
The objective of this study is to provide suitable approximations of effective permeability for m... more The objective of this study is to provide suitable approximations of effective permeability for magnetic concentration cores. This core has dumbbell-shape, so that the magnetic flux is concentrated to the coil winding part of the core. It is well known that the demagnetizing factor strongly depends on the core shape which defines the effective permeability. Although several researchers have already proposed an approximation for a dumbbell-shaped core, it cannot take into account the flange part length. In this paper, a novel approximation for dumbbell-shaped core is proposed. It is based on the demagnetizing factor and correction terms related to the aspect ratio of both the flange and coil winding part. From experimental results, the validity of the approximation is confirmed.
EPJ Web of Conferences, 2013
This paper presents magnetic flux concentration methods for magnetic energy harvesting module. Th... more This paper presents magnetic flux concentration methods for magnetic energy harvesting module. The purpose of this study is to harvest 1 mW energy with a Brooks coil 2 cm in diameter from environmental magnetic field at 60 Hz. Because the harvesting power is proportional to the square of the magnetic flux density, we consider the use of a magnetic flux concentration coil and a magnetic core. The magnetic flux concentration coil consists of an aircore Brooks coil and a resonant capacitor. When a uniform magnetic field crossed the coil, the magnetic flux distribution around the coil was changed. It is found that the magnetic field in an area is concentrated larger than 20 times compared with the uniform magnetic field. Compared with the aircore coil, our designed magnetic core makes the harvested energy tenfold. According to ICNIRP2010 guideline, the acceptable level of magnetic field is 0.2 mT in the frequency range between 25 Hz and 400 Hz. Without the two magnetic flux concentration methods, the corresponding energy is limited to 1 µW. In contrast, our experimental results successfully demonstrate energy harvesting of 1 mW from a magnetic field of 0.03 mT at 60 Hz.
Smart Sensors, Measurement and Instrumentation, 2013
We propose the design of AC–DC converter for a magnetic energy harvesting device. When this devic... more We propose the design of AC–DC converter for a magnetic energy harvesting device. When this device is used as an energy source for wireless sensor applications, the DC output voltage should be larger than 1.5 V. First of all, we investigate the efficiency of conventional circuit whose has power conditioning module varied input power. It is found that efficiency of this module is at most about thirty percent. In the next place, we investigate the basic properties of an AC–DC converter with a Cockcroft-Walton circuit. Experimental results reveal that the optimum conditions are related with the number of steps, input voltage, input resistance, and dummy load. From a magnetic field of 675 nT at 60 Hz, the new magnetic energy harvesting device used Cockcroft-Walton circuit can provide a DC output voltage of 1.5 V. Compared with the previous device installed conventional power conditioning module we developed, the required magnetic field is as low as 1/400 in amplitude. In contrast, the measured efficiency of the device is better than 80 % when the magnetic field is larger than 20 μT.