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Your search keyword '"Orikawa, Koji"' showing total 109 results
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109 results on '"Orikawa, Koji"'

8. A Winding Structure of Air-Core Planar Inductors for Reducing High-Frequency Eddy Currents.

Author

Orikawa, Koji, Kanno, Shotaro, and Ogasawara, Satoshi

Subjects
*EDDY current losses, *EDDY currents (Electric), *EDDIES, *POWER amplifiers, *MAGNETIC flux leakage, *PRINTED circuits
Abstract

High-frequency converters with high power density have shown promise in recent years. Air-core planar inductors built with printed circuit boards can eliminate problems associated with the use of magnetic materials, such as iron loss and magnetic saturation. However, conventional air-core planar inductors suffer from eddy current loss. Eddy currents affect the resistance and inductance of the inductor. This article proposes a stranded wire structure to reduce eddy currents more than that in the conventional spiral wire structure. Eddy currents can be reduced by splitting the windings as well as currents of each split winding are balanced in the proposed structure. Seven types of air-core planar inductors were built, and their resistances, inductances, and impedances were measured to evaluate the effects of different structures on eddy currents. Furthermore, the temperature distribution of the planar inductors was measured while supplying a sinusoidal voltage with a power amplifier. The experimental results demonstrate the usefulness of the proposed stranded wire structure. Furthermore, the experimental result shows that the stray capacitance of the inductor can be reduced as a by-product of the proposed stranded wire structure. [ABSTRACT FROM AUTHOR]

Published
2022
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16. Variable Flux Memory Motor Employing Double-Layer Delta-Type PM Arrangement and Large Flux Barrier for Traction Applications.

Author

Tsunata, Ren, Takemoto, Masatsugu, Ogasawara, Satoshi, and Orikawa, Koji

Subjects
DEMAGNETIZATION, MAGNETIZATION, MEMORY, MAGNETIC circuits, MAGNETIC flux, PERMANENT magnets
Abstract

This article consists of two important topics regarding variable flux memory motors (VFMMs). The first topic is magnetization characteristic analysis of VFMMs having a double-layer permanent magnet (PM). Two-dimensional simulations are executed to clarify relationship between magnetization characteristic and ratio of the double-layer PM. In addition, a prototype of a compact size VFMM is fabricated, and experiments are also carried out to investigate accuracy of magnetization characteristic analysis. The second topic is the proposed VFMM employing double-layer delta-type PM arrangements and extended flux barriers for traction applications. Conventional VFMMs have three critical issues, which are as follows: asymmetric positive and negative magnetizing current pulses, increase in the iron loss due to harmonics caused by demagnetized variable flux PMs (VPMs), and unintentional demagnetization of VPMs under load condition. The proposed VFMM can overcome the abovementioned problems by employing double-layer delta-type PM arrangements and extended flux barriers. In addition, the proposed VFMM achieves much higher efficiency than that of the target motor mounted in TOYOTA Prius fourth-generation over a wide operating range. [ABSTRACT FROM AUTHOR]

Published
2021
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26. Investigation of Operational Characteristics and Efficiency Enhancement of an Ultrahigh-Speed Bearingless Motor at 100 000 r/min.

Author

Fu, Yu, Takemoto, Masatsugu, Ogasawara, Satoshi, and Orikawa, Koji

Subjects
MAGNETIC suspension, PERMANENT magnet motors, MOTORS
Abstract

This article introduces the operational characteristics of an ultra-high-speed bearingless motor with 2-pole concentrated motor windings and 4-pole concentrated suspension windings. Experiments with a prototype machine indicate that iron loss is the largest component of losses in the proposed bearingless motor. Therefore, in order to reduce the iron loss, comparison of the experimental results and the 3D-FEM results is discussed. As a result, because it is turned out that iron loss of the switching frequency component accounts for a large proportion in total iron loss, a method of enhancing efficiency of the proposed bearingless motor by means of high switching frequency using SiC-MOSFET is examined. The experimental results with the examined method show that the prototype machine can attain the high efficiency of 94.3% at rated operation of 1.70 kW and 100,000 r/min in spite of including suspension input power for magnetic levitation. In addition, operational characteristics comparison of the bearingless motor at switching frequency of 40 kHz, 80 kHz and 120 kHz is discussed in detail. [ABSTRACT FROM AUTHOR]

Published
2020
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38. Common-Mode Voltage Attenuation of an Active Common-Mode Filter in a Motor Drive System Fed by a PWM Inverter.

Author

Takahashi, Shotaro, Ogasawara, Satoshi, Takemoto, Masatsugu, Orikawa, Koji, and Tamate, Michio

Subjects
PULSE width modulation, NOISE generators (Electronics), MOTOR drives (Electric motors), ELECTROMAGNETIC interference, ELECTRIC potential
Abstract

The switching speeds of next-generation power semiconductor devices, such as those made of silicon carbide and gallium nitride are roughly ten times those of conventional devices (e.g., silicon insulated-gate bipolar transistors). This increases the frequency range of the electromagnetic noise accompanying the switching operations of pulsewidth modulated (PWM) converters and worsens the influence of radiated noise. The authors have previously proposed an active common-mode filter (ACF) that reduces the radiated noise from the power cables connected to a PWM converter and evaluated its effect in reducing radiated noise by using a function generator as a common-mode (CM) noise source. In this paper, the ACF is applied to a motor drive system fed by a three-phase PWM inverter, and the attenuation characteristics of the CM voltage are evaluated. To avoid saturating the ACF, the combination of an active common-noise canceller and the ACF is discussed. The experimental results show that the system constructed in this paper can suppress the CM voltage produced by the PWM inverter over a wide frequency range from 100 to 100 MHz. [ABSTRACT FROM AUTHOR]

Published
2019
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