Hybrid power source three level inverter is proposed as a main circuit system with energy storage device for increasing regenerative power. This paper proposes a charge and discharge control method to utilize the regenerated energy. The proposed method is verified by experimental tests with a scaled-down model and numerical simulation.

Assurance technology is known as a technology for replacing a system without stopping it under various circumstances. This paper discusses the application of assurance technology to railway signalling for smooth migration.

East Japan Railway Company applied assurance technology to the digital automatic train control (D-ATC) system introduced to operate the most crowded lines in the Tokyo metropolitan area. It was not only able to contribute to accelerating construction and improving the reliability of D-ATC, but also effective in enhancing the functionality of railway signalling which directly relates to railway business.

In order to increase the power density of power converters, reduction of both the loss and the volume of the inductor is essential. However, it is difficult to calculate the iron loss of the inductor with the Steimetz equation or the improved generalized Steinmetz equation (iGSE) because those calculation methods do not consider the loss dependency of pre-magnetization. Hence, we have to repeat the re-design process in order to reduce the inductor loss or the inductor volume. In this paper, the authors propose an accurate loss calculation method for the inductor used in the buck-chopper circuit that is based on the iron loss characteristic considering pre-magnetization. In addition, the overall loss of the inductor is compared among three typical magnetic materials, such as iron powder, sendust, and ferrite, which have different iron loss characteristics for pre-magnetization. As a result, the sendust-based inductor achieves both the same loss reduction and a smaller volume compared with the ferrite-based inductor. From these studies, it is concluded that the proposed loss calculation method, which takes into account the loss dependency of pre-magnetization, is useful for optimum design of the inductors.

The inductor losses in a three-phase AC filter inductor used in a three-phase pulse-width modulation (PWM) inverter are evaluated. First a three-phase inductor is designed to obtain the same value of inductance for each phase. Then, based on the design, a three-phase inductor that uses two magnetic materials is proposed. The conversion efficiency of a 1kVA three-phase PWM inverter that uses the conventional and proposed AC filter inductors is simulated. Simulation results show that conversion efficiency improves. Finally, the conversion efficiency of an actual three-phase 1kVA PWM inverter that uses the conventional and proposed AC filter inductors is measured. In the experiment, the conversion efficiency obtained for the case of the proposed inductor improves by approximately 1% at low power load as compared to the conventional inductor. Furthermore, the calculated inductor loss es are in good agreement with measured losses. Improvement in efficiency is verified trough simulations and experiments.

This paper provides a theoretical and experimental discussion on a unidirectional isolated dc-dc converter equipped with a high-frequency transformer. It focuses on an application of the dc-dc converter to an auxiliary power supply for electric commuter trains. This specific dc-dc converter is required to tolerate sudden and frequent changes in the catenary voltage with a nominal value of 1.5kV_dc, and has to maintain a constant output voltage. This auxiliary power supply is characterized by an input-series, output-parallel circuit configuration of two identical unidirectional isolated dc-dc converters. This configuration allows the dc-dc converter to eliminate a boost converter at the front end and a switchover circuit between series and parallel connections. The 600-V_dc, 6-kW, 16-kHz downscaled experimental system using SiC-MOSFET/SBD modules is designed, constructed and tested to verify the validity of the specially-constructed control system for regulating the dc output voltage to a reference of 150V_dc. Experimental waveforms show that the dc output voltage is well regulated even when a sudden input voltage change from 600 to 350V occurs, and a sudden load change from 3 to 6kW occurs.

This paper proposes a new fault-tolerant vector control method for permanent-magnet synchronous motors (PMSMs) that are equipped with a set of three Hall-effect sensor (HES) elements. Vector control for PMSMs requires precise rotor position information and gets it from high-resolution position sensors mounted on the rotor such as an encoder and resolver. However, these sensors have several drawbacks in terms of cost, volume, reliability, etc. An HES, which provides very rough position information with a 30-degree error, is a possible candidate for overcoming these drawbacks. This paper proposes a new method that can synthesize position information with sufficient precision for vector control from an HES signal. Even if two of the three HES elements break down, the proposed method allows the PMSM to operate by using the signal from the remaining healthy element.

The speed control system of an AC servomotor generally comprises a proportional-integral (PI) controller and current limiter. When the output of the speed PI controller is limited by the current limiter, a windup phenomenon and unstable response often occur. This paper proposes a new anti-windup control for the speed control system of an AC servomotor. In the conventional method, when the output of the speed PI controller is limited by a current limiter, the input of the integrator is revised by using the difference between the input and output of the limiter. In the proposed method, the input of the integrator is revised by considering an accelerating torque component. This allows the output of the integrator to converge to the torque current corresponding to the load torque. As a result, speed overshooting is suppressed, and a good transient response is provided. Furthermore, using a weight function to revise the input of the integrator can further suppress overshooting. The effectiveness of the proposed anti-windup control method was verified through experiments and numerical simulation.

Recently, interior permanent magnet synchronous motors (IPMSMs) have been mainly utilized as the traction motors of eco-friendly vehicles. Moreover, the permanent magnet used for IPMSMs is an important factor that determines their performance. In general, the permanent magnet with a higher remanence increases not only the magnet torque—which in turn increases the torque—but also the iron loss. A rotor structure that is suitable for the permanent magnet, therefore, has to be researched. This paper uses a virtual permanent magnet (VPM) designed to have higher remanence. The single-layered model with the conventional magnet, the single-layered model with the VPM, and the double-layered model with the VPM are compared to investigate the influence of the arrangement and the properties of permanent magnets on the performance of IPMSMs for automotive applications. In addition, the stack length of the best of these motors is reduced in order to downsize it and reduce its volume, and the iron core material is changed to a low iron loss material in order to improve the efficiency. It is observed that the double-layered model with the VPM produces the highest torque and efficiency. Furthermore, both the downsized model and the model with the low iron loss material have a higher efficiency.

In recent years, inductive power transfer (IPT) systems have been actively studied. This paper describes the development trend of inductive power transfer systems since the 1970s, focusing on the transmission frequency, transmission power, and the coupling coefficient, on the basis of a survey of papers published by IEEJ and IEEE. The transmission power shows close correlation with the transmission frequency. By contrast, the coupling coefficient does not show correlation with either the transmission frequency or the transmission power.

Silicone gels have been used as an encapsulant of power electronics modules. We investigated electric treeing in silicone gel under AC voltage. The growth patterns of the trees depended on the frequency of the applied voltage. At low frequencies (10mHz to 10Hz), a bubble appeared at the tip of needle electrode, and a simple tree grew at 10Hz. Trees had many small branches at 350 and 400Hz and did not appear at frequencies over 450Hz.