It is commonly assumed that operating trains at very high frequencies requires a substantial increase in the capacity of electric traction power supply systems, particularly to deal with surge in power demand caused by service disruptions. However, this assumption may not hold under “synchronisation control” which automatically minimises headway between consecutive trains on a railway controlled by pure moving block (PMB) while maintaining PMB's safety constraints. In this study, we tested this hypothesis through simulations using a simplified model under two different scenarios. In the first scenario, nine passing trains followed one departing train at a station with the shortest possible headways. A severe delay in the departure of the leading train resulted in a peak power demand slightly less than twice that of a single accelerating train. In the second scenario, 15 trains operated according to two different timetables on a circular 15-station railway line. In this case, the impact of departure delays on peak power demand was difficult to identify. These results support the validity of our hypothesis.

We introduce an isolated Class-Φ₂ DC-DC converter that uses a synchronous rectification method. To evaluate the effectiveness of the method, we compare the power conversion efficiency of the aforementioned with that of a Class-Φ₂ DC-DC converter employing diode rectification. Both converters are designed and constructed to operate at a switching frequency of 1MHz. Experimental results indicate that synchronous rectification improves power conversion efficiency by 6.3% compared to diode rectification. The output power of the isolated Class-Φ₂ DC-DC converter using synchronous rectification reaches 2.9W, achieving a power conversion efficiency of 87.5%. Losses in the rectifier stage are evaluated by measuring the V - I characteristics of the rectifier components in both circuits.

This paper presents a design methodology for low-voltage converters and an associated cooling structure necessary for applying a modular multilevel converter (MMC)-based active power filter (APF) using low-voltage Si-MOSFETs, specifically for inverter-driven air conditioners. The voltage detection circuit is simplified by referencing the MMC neutral point, eliminating voltage concentration on specific cells during APF shutdown. The proposed MMC-APF comprises 36 low-voltage Si-MOSFETs, each with an on-resistance of several mΩ, effectively distributing heat generation and limiting power loss to less than 1W per device. By utilizing airflow from the air conditioner's outdoor unit fan, the system operates without additional heatsinks or cooling fans. Experimental results confirm that the proposed MMC-APF achieves purely sinusoidal source currents with a unity power factor, while reducing total loss by 38.6% compared to a conventional two-level IGBT-based APF.

The magnetic composite ring motor aims to reduce the eddy current loss in permanent magnets during high-speed rotation by installing magnetic material on the stator, thereby suppressing temperature rise. The results showcased the influence of the composite ring material on temperature rise suppression was investigated. As a result, under conditions of 30,000r/min and 500W, a temperature rise reduction of more than 10°C was confirmed compared to a conventional open-slot motor.

Superconducting Maglev employs a wireless power transfer system to supply on-board power. The ground inverter and on-board converters independently regulate the supplied power, stabilizing the power system without requiring communications. Given the diverse conditions affecting the power supply control, particularly the characteristics of the primary loop, deriving a mathematical model for stability assessment is an efficient approach. The proposed stability evaluation method has two key components. The first is the derivation of the transfer function (complex coefficient transfer function), which determines the circuit's output RMS current based on the input alternating voltage under two-input and two-output conditions. The second is the segmentation of the time-varying characteristics into discrete time points with stability assessed at each point using the proposed transfer function. Verification results confirm that the proposed method enables stability assessment and offer a framework for expanding the stability range.

Simple and cost-effective methods for air entrainment detection are required for the efficient maintenance of pump systems. Recently, motor current signature analysis (MCSA) has been gaining attention for motor fault detection. In this paper, we review the characteristics of motor current signals in an air entrainment state and propose an MCSA technique for air entrainment detection. We observed that the foot around the fundamental harmonic spectrum in the power spectral density of current signals increased with an air entrainment. Based on these results, we propose defining a characteristic value which reflect this feature.

This study proposes a compact coil arrangement for a three-phase wireless power transfer (WPT) system with 12 coils. By rotating each coil pair, magnetic coupling is reduced, enabling interference cancellation with a smaller radius. A 22-kW prototype was tested in a 10-meter anechoic chamber, confirming compliance with CISPR 11. The proposed method reduces coil area by 58.1% while maintaining emission suppression performance.

Our research focuses on the modeling of rare-earth-free switched reluctance motors. We study both conventional and transverse flux SRMs through numerical analysis and experimental validation to improve efficiency and explore new operating regions.