This paper proposes a simplified evaluation method of drive characteristics for claw-pole-type permanent magnet stepping motor. The proposed method consists of a geometric flux-tube-based nonlinear magnetic analysis and a dynamic simulator based on the analytical expression of magnetizing curves obtained through nonlinear magnetic analysis. The validity of the model was verified based on relevant experimental results for the static and dynamic characteristics of the prototype. The proposed analysis provides accurate and extremely quick magnetizing curve computation compared to three-dimensional finite element analysis (3D-FEA). The versatility of the proposed method was verified by comparing it with 3D-FEA in terms of the pull-in torque calculation accuracy for varying design parameters. Moreover, the distance between adjacent claw poles significantly influenced the pull-in torque.
Recently, energy harvesting has attracted increasing attention. The present study focuses on vibration generators based on piezoelectric elements by proposing an internal capacitor cancel control (ICCC) rectifier to improve the output power. The proposed rectifier cancels the internal capacitor to improve the output power while retaining the maximum output power. Accordingly, this paper experimentally demonstrates the improvement in output power by using the ICCC rectifier compared to conventional circuits and the previous proposed circuit.
The switching noise mechanism of a high voltage superjunction-MOSFET loaded into a power supply is analyzed. The device model is developed using BSIM3 MOSFET model with voltage-dependent capacitors. Inductive load switching with test-circuit parasitic elements is simulated, and the switching surge generated during turn-off transient is discussed. A sharp drop of drain-source capacitance (Cds at the turn-off transient causes high voltage ringing, whose frequency is determined using total capacitances and stray inductances in the power loop circuit. The optimization of Cds-voltage characteristic and additional Cgs with small capacitance are proposed as an effective method for suppressing surge generation. The voltage ringing level is improved by slightly modifying the Cds-voltage curve and additional Cgs. In addition, test results show that the radiated EMI decreased.
Power supplies for gas shielded arc welding with high control speed are being increasingly investigated for improving the welding quality and reduce spatter. In this study, the effect of current change on droplet behavior was evaluated, when high-speed current control is performed at a control frequency of 300kHz through the application of an interleaved back converter to the welding power supply. Consequently, it was confirmed that spatter can be reduced by controlling the current at a high speed.
Short cruise range is a major issue of electric vehicles. Dynamic wireless power transfer (DWPT) is proposed to solve this problem as it can reduce batteries on electric vehicles. Thus, well-to-wheel is improved by the reduction of drive resistance due to lighter weight of vehicles. Moreover, greenhouse gas emission via the manufacturing of batteries is also reduced. This work evaluates the reduction of lifetime greenhouse gas emission by DWPT from production, generation, and driving by simulation with actual measurement data. It is revealed that compared to conventional electric vehicles, DWPT can not only realize a 14% reduction of greenhouse gas by generation and driving but also 90% reduction via the manufacturing of batteries.
In this paper, we propose asymmetric winding structure to achieve a low torque ripple and high slot fill factor. Existing methods developed for this purpose improve the winding factors of harmonics and the slot fill factor by ensuring that the winding arrangement and number of turns for each coil are asymmetric. In contrast, an asymmetric winding structure generally lowers the symmetry of the magnetomotive force of the stator and generates electromagnetic excitation forces with lower spacial order modes, resulting in increased vibration. Therefore, in this study, we aim to improve the winding factor and the slot fill factor by changing the winding arrangement and the number of turns while considering the symmetry of the electromagnetic field. First, the working principle of techniques for improving the characteristics of the proposed winding structure are discussed. Thereafter, the results of magnetic field analysis and the verification of the said improvements to the asymmetric prototype, along with the effects, are presented.
In the case of driverless trains, the ability of abnormal-sound detection which traditionally has been based on crew's ears will be lost. To make up this, this paper proposes an abnormal-noise detection system using microphones under trains. The feature of the system is to determine the abnormalities on railway track not only based on the sound but also the velocity and the position of the train. To accomplish that, the system uses neural network which is able to predict normal sound level based on the velocity and the position.
In the system, when the running sound is extremely larger than the predicted normal sound, it would be determined as abnormal sound. To verify the effectiveness of the system, test running is conducted where the test train passes on a stone located on the rail. Through the test running, we have confirmed that the system would be able to detect the abnormal sound due to the stone in case the train passes on the stone at over 20km/h.