This report presents a rotor design and actual test of a 24kr/min high-speed motor considering its centrifugal force, rotor dynamics, and bearing lubrication method. Consequently, applying a rotor structure with two bridges and tail barriers causes the analyzed maximum principal stress at 24kr/min of 346MPa to be smaller than the yield stress of 400MPa. The actual test of an elemental prototype was conducted to validate the proposed design. The experimental results indicate that there were no resonance points up to 24kr/min, the maximum vibration amplitude of the 1N component was 8µm, and the minimum mechanical loss was 1.78kW at 24kr/min when the lubricant was 50°C and 1.3L/min.

This paper proposes a spike noise reduction method for a half-bridge circuit in synchronous rectification during zero-cross switching. A sharp dV/dt is caused by the switching operation of the superjunction-MOSFET (metal-oxide semiconductor field effect transistor) loaded into the half-bridge circuit. Inductive load switching with the device model, which is developed using BSIM3 with voltage-dependent capacitors, is simulated. The mechanism of the sharp dV/dt generated during switching transient in deadtime is discussed. The pre-charge circuit with a low-voltage MOSFET, a SBD (Schottky barrier diode), and an auxiliary power supply is added between the drain-source terminal. Drain-source capacitance is decreased as a function of the pre-charge voltage. The simulated results show that the 30V pre-charge effect reduces dV/dt from 23.4V/ns to 8.9V/ns. The half-bridge circuit with the pre-charge circuit was prototyped, and the results of the switching waveforms and dV/dt showed good agreements with the simulated results.

In recent years, various studies have been conducted to popularize electric vehicles in order to achieve carbon neutrality. Toward this end, the method of dynamic wireless power Transfer (DWPT) for these vehicle is attracting considerable attention as it can shorten the charging time and contribute to battery downsizing. However, since a vehicle passes by in a short period of time, the duration for which the vehicle is not on the transmission coil is long, and the standby loss on the transmission side causes a loss of efficiency. This study proposes a new vehicle detection method using the voltage from divider circuit of the transmission coils in the DWPT system. The proposed method is expected to reduce standby losses due to copper losses in the transmission coils and the inverter losses. The effectiveness of the proposed system has been verified through experiments.

We developed a method for creating energy-efficient timetables by reducing powering energy consumption and making effective use of regenerative energy, through mathematical optimization. This approach incorporates passenger convenience ensuring that the total traveling time from the starting station to the terminal station of each train remains consistent with the original timetable. This paper describes the details of the method for creating energy-efficient timetables and reports the results from a case study using real-world line data. In this case study, energy-efficient improvements of 7.4% and 4.9% were achieved when auxiliary power is set according to the ambient temperatures equivalent to 15℃ and 30℃ respectively.

This paper presents a demagnetization evaluation using an interior permanent magnet synchronous motor (IPMSM) for battery-powered electric vehicles with radially oriented, arc-shaped, hot-deformed magnets. Specifically, using actual measurements, we reproduced the reverse magnetic field and high-temperature conditions that were set in the electric-field analysis, and we considered evaluation methods that minimized the difference between the actual measurements and those of the electric-field analysis. The results of the actual measurements corresponded to those of the electric-field analysis, and demonstrating the validity of the measurement methods.

Dynamic wireless power transfer (DWPT) has garnered significant research attention in recent years as a means to facilitate the adoption of electric vehicles. Implementing this technology requires embedding transmission coils into roadways, and numerous studies have explored the practicality of such buried coil systems. In this paper, we introduce an edgewise coil design that offers enhanced heat dissipation and cost efficiency for use as transmitting coils in DWPT systems. Experimental comparisons were conducted between traditional litz wire coils and the proposed edgewise coils, focusing on transmission characteristics and heat generation when embedded in the road. The results demonstrate that the edgewise coils maintain transmission performance comparable to that of conventional systems while reducing coil temperature rise by 4.2°C. These results underscore the potential of edgewise coils as an effective and practical alternative for DWPT applications.

The paper presents a control method for three-phase grid-tied inverters based on V/f control. V/f control is used to control the speed of permanent magnet synchronous motors (PMSMs). However, speed control cannot be achieved with the grid-tied operation because the grid-tied inverter cannot control the power grid frequency. The proposed method establishes the relationship between an output power command, output power, and output frequency for V/f control, thereby functioning as a speed controller. Thus, the proposed method achieves supped control during grid-tied operation using V/f control. Moreover, the control response of the proposed method is analyzed to design the control parameters. The experimental results are demonstrated using a 2-kW inverter.

This study presents a mathematical modeling approach to design a feedback control system in a ZETA converter to facilitate pole-zero cancellation. The state-space averaging method was employed to derive the transfer functions, and the number of terms in these functions was reduced by imposing conditions on the circuit parameters that are consistent with the circuit design methodology and do not adversely affect circuit operation. Moreover, the transfer functions are systematically organized based on assumptions regarding the relationship between parasitic resistance and damping coefficient. This organization elucidates the relationship between resonance frequencies, damping coefficients, zero frequencies, and circuit parameters within the transfer functions.

Additionally, because of the resonance elements, the ZETA converter imposes severe constraints on the stability margin in control system design. As the current-mode control (CMC) can suppress the effects of resonance elements, the one-round transfer function of the feedback control system with CMC applied to the ZETA converter is modeled. The modeling mathematically evaluates the CMC control systems with feedback of each current for the two inductor currents in the ZETA converter. The results indicate that the control system with feedback of the inductor current near the output part can more effectively suppress resonance elements.

Chargers have become an indispensable component with the increase adoption of electric vehicles. A charger is composed of multiple power converters and its operation has become increasingly complex. It is necessary to understand the complex behavior to ensure system stability during control design.

The transfer function of a system composed of multiple power converters can be derived using the state averaging method. However, the formulated state equation matrix has a large order making difficult to derive the transfer function. This paper proposes a method to analyze the behavior of the system using the transfer functions of the power converters that constitute the system. To facilitate the analysis, we adopted a simple two-stage configuration of a non-isolated buck converter. The circuit model and model derived using the proposed method achieved a high level of agreement, confirming the effectiveness of the proposed method.

Marine life survey up to a depth of ∼20m is conventionally conducted using a belt transect method that relies on human divers. This paper describes a new technology and experimental results of a marine life survey system that uses image detection AI. This system automatically creates a database of the growth and distribution of fishes and coral leaf. Consequently, more detailed surveys of marine life can be conducted over larger areas of ocean.

This paper clarifies the influence of inductance harmonics on the 6kth-order torque ripple in vector control for switched reluctance motors (SRMs) and proposes a torque ripple suppression control method based on two SRM mathematical models with different electrical angular frequencies. The following is clarified when deriving the 6kth-order torque ripple estimation equation for arbitrary inductance harmonics: In the case of vector control modeled at a frequency of twice the electrical angular frequency, up to (6k+4)th-order inductance must be considered to estimate the 6kth-order torque ripple. Meanwhile, vector control modeled at a frequency of the electric angular frequency must consider up to (6k+2)th-order inductance. The proposed method estimates and suppresses torque ripple using the proposed torque estimation equation. Experimental results show that the proposed method can suppress the 6th-order torque ripple by 88.2% and 89.2% for the two types of vector control. Additionally, the proposed method reduced the vibration of the SRM caused by torque ripple by 18dB and 15dB for the two types of vector control.

This paper presents a novel topology optimization method for electrical machines, in which a Quadratic Unconstrained Binary Optimization type (QUBO-type) response surface is constructed using analytical data obtained offline. Moreover, quantum annealing is utilized to enhance the convergence of the optimization. Since the proposed method facilitates reduction in the number of inferior solutions in the optimization, convergence can be improved. The method is applied to an optimization problem of a magnetic head to verify basic operation of quantum annealing. Furthermore, the rotor of an interior permanent magnet motor (IPM motor) is optimized using the proposed method. The numerical results confirmed that the proposed method can enhance convergence of optimization without increasing computational costs.

This paper proposes a method for hydrogen flow rate estimation in fuel cells using time-series prediction with machine learning based on existing measurement values such as fuel cell output power, output current, and purge timing. In the proposed method, the appropriate combinations of feature quantities and sequence length are selected using a genetic algorithm. As a result, the proposed method reduces the mean absolute error (MAE) by approximately 50% compared to the linear approximation between the current and hydrogen flow rate.

This article introduces Power Electronics Laboratory at Department of Electrical and Electronic Engineering, Kyushu Institute of Technology, which focuses on reliability-related issues of power electronic converters including power semiconductor devices and capacitors.