Flywheels have several advantages such as long life, high reliability, and high environmental resistance. This paper describes the application of flywheel to uninterruptible power supplies that rotate a motor-generator at commercial frequencies of 3000min^-1. Conventional systems that use flywheel generators require high-capacity semiconductor power converters for energy conversion. Moreover, a specially designed generator is required because the generator operates at variable speed. To overcome these weaknesses, this paper proposes a flywheel generator using a planetary gear, which is a mechanical shaft coupling mechanism. The use of a planetary gear enables the flywheel and generator to rotate at different speed. As a result, even if the flywheel speed drops during a power outage, the generator speed can be kept constant. This paper reports on the design guidelines and experimental verifications for a 1-kW system.

A train schedule is determined the transport capacity and track layout based on passengers demand.

A railway line has several schedules, making schedules are necessary evaluated for quantity comparison. In particular, when a transport disorder occurs, quantity evaluation is required as a tool for adopting an optimal rescheduling plan.

Therefore, this paper proposes a train schedule quantity evaluation method from three points of view; passenger convenience, operation simplicity, and operation margin robustness.

Passenger convenience is calculated based on the time loss by the passenger, operation simplicity is calculated turning number of switches, and operation margin is calculated based on the train interval time at stations and number of train sets.

The proposed method is applied train schedules, and I demonstrate that the derived values each train timetables.

This study aims to improve the efficiency of an induction motor. The efficiency was measured under a load test using the inverter drive to verify the loss reduction effect when the winding changeover was applied. The stray load loss of series connection with a 184V synchronous 3 pulse could be reduced by 78% compared to the parallel connection with a 92V asynchronous pulse width modulation. Moreover, it was confirmed that the efficiency of the series connection is improved by approximately 4.4% compared to the parallel connection. Based on the above, it is confirmed that switching between series and parallel connections using a winding switcher can increase the efficiency of induction motors.

This study aims to increase the power density of electromagnetic pumps for automatic pouring at casting sites by clarifying the magnetic force required for the electromagnetic transport of liquid metal. This paper reports the results of clarifying the relationship between flow and electromagnetic force by fabricating an experimental machine that simulates an electromagnetic pump. The flow velocity is measured when a low-melting temperature metal (Gallium) flows due to the Lorenz force, and the relationship of its flow between the excitation frequency and magnetomotive force is experimentally clarified. Furthermore, the spatial distribution of flow velocity and its relationship with the flow is clarified. Consequently, a flow map of liquid gallium was obtained, and reveals that the driving conditions are high-slip with a slip of 0.97 or more. Moreover, the magnetomotive force can contribute to the to flow more effectively than the excitation frequency under a narrowing gap between gallium and the machine.

In this study, we describe a temperature calculation method with a large network solver for transposed armature windings of a turbine generator. As is well known, a significant amount of circulating current flows within strands in armature bars. Therefore, it is critical that physical transposition of the strands should be considered for temperature calculation. We developed a calculation tool that can extensively handle the circulating current as well as complicated temperature distribution of the cooling media in the generator. The calculated result indicates that temperature distribution in generators can have a wide range as opposed to detectable temperatures depending on the design.

This study reports on the common-mode (CM) voltage suppression of a passive common-noise canceller (PCC), which can cancel CM noise generated by pulse-width-modulation (PWM) inverters. The proposed PCC is characterized by the installation position to the DC side of an inverter instead of the AC side. Compared to a conventional AC-side PCC, the proposed PCC can reduce the window area of the CM transformer to enable size and weight reduction of the PCC. This study describes the design of the PCC and shows the experimental CM voltage suppression effect with a voltage-source PWM inverter.