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Aihara S.,Nishi Nippon Electrical Wire and Cable Co. | Shimoji H.,Oita University | Todaka T.,Oita Prefectural Organization for Industry Creation | Enokizono M.,Oita Prefectural Organization for Industry Creation
IEEE Transactions on Magnetics | Year: 2012

This paper presents measured local vector magnetic properties in a transformer type model core made of a laser-scratched grain-oriented electric steel sheet by using a vector-hysteresis (V-H) sensor. The V-H sensor consists of B-needle probes for measurement of the magnetic flux density vector B and double H-coil for measurement of the field strength vector H. The distance between the B-needle probes was shortened to be 2.5 mm and a 2 mm × 2 mm-sized double H-coil was mounted on the sensor head to realize higher resolution. The measurement accuracy of the B-needle probes was confirmed with a spatial probe, which can change the needle distance from 2 mm to 20 mm. The results show that the detailed local two-dimensional vector magnetic properties depending on laser-scratches are measurable with the developed new sensor. © 1965-2012 IEEE. Source


Ooka K.,Oita University | Kajiwara T.,Oita University | Aihara S.,Nishi Nippon Electrical Wire and Cable Co. | Enokizono M.,Oita University
IEEE Transactions on Magnetics | Year: 2014

To reduce power loss of transformers further from now on and to raise efficiency, we have measured magnetic property distributions in a three-phase tripod V-connection transformer model core. For the measurement, we have developed a localized vector magnetic property measurement system consisting of a three-axis positioning system, a vector magnetic sensor (V-H sensor), and PC. The measured results showed that rotational magnetic fluxes with a large axis ratio were generated in the V-junction parts of the transformer model core, and large iron loss was observed. To reduce the iron loss near the V-junction parts, we have tried to change local magnetic characteristics of the electrical steel sheet near the V-junction parts by using laser irradiation. The effect of the laser irradiation on the local magnetic properties is evaluated by measuring distributions of the local magnetic properties. © 1965-2012 IEEE. Source


Aihara S.,Nishi Nippon Electrical Wire and Cable Co. | Aihara S.,Oita University | Todaka T.,Oita University | Enokizono M.,Oita University
Przeglad Elektrotechniczny | Year: 2011

Two-dimensional vector measurement has become popular as an accurate evaluating method, which can measure the relationship between the magnetic flux density vector B and the magnetic field strength vector H. In order to improve the resolution of the two-dimensional vector magnetic measurement, 4mm-square-sized double H-coil was manufactured and evaluated with a developed evaluation system, which consists of a standard solenoid coil and a high-precision turntable. The V-H sensor combined the H-coil with double needles, was applied to measure distributions of local magnetic characteristics in a model core. Source


Aihara S.,Nishi Nippon Electrical Wire and Cable Co. | Todaka T.,Oita University | Enokizono M.,Oita University
Journal of Electrical Engineering | Year: 2013

This paper presents a small-sized vector-hysteresis sensor (V-H sensor), which consists of piercing B-needles and double Hcoil. The B-needle probe can break through the insulation coating of silicon steel sheets like a drill. The H-coil is made in very small size and the outside dimension is 4mm×4mm. The magnetic flux density vector B and the field intensity vector H are measured with the B-needle probe and the double H-coil, respectively. The influence of the insulation coating on distributions of vector magnetic properties in transformer model cores is investigated in measurements with the developed very small-sized V-H sensor.© 2010 FEI STU. Source


Kitajima J.,University of Miyazaki | Sakoda T.,University of Miyazaki | Watanabe K.,Nishi Nippon Electrical Wire and Cable Co.
IEEJ Transactions on Fundamentals and Materials | Year: 2014

To locate partial discharges (PDs) in cross-bonding cables where current pulses due to PDs might be divided, we paid attention to phases of current pulses obtained by six CT sensors arranged at both sides of 3-phase of the cables. The accuracy of PD location, obtained by using time difference between arrival times of current pulses from specified phase, was relatively high even for cross-bonding cables. © 2014 The Institute of Electrical Engineers of Japan. Source

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