The traction motors used in electric vehicles (EVs) should satisfy trade-off requirements such as high torque at low speed, high efficiency at low torque regions, and a constant output in a wide speeds. To achieve this, several types of motors such as variable flux machines and variable parameter machines have been developed. Our research team focuses on a consequent-pole-type ferrite permanent magnet (PM) axial gap motor with field windings, in which the magnetic flux density can be varied. Although consequent-pole-type motors have previously been researched, no extant study has focused on the influence of the slot combination on the motor performance. This study investigates the magneto-motive force and rotor permeance of several motors.

Recently LED lighting apparatus are becoming more popular and well received by users. An offline LED apparatus needs to have electrolytic capacitors inside to supply LEDs with a regulated DC voltage. Although LEDs are characterized by longevity, the shorter lifetime of the constituent electrolytic capacitors limit the lifetime of the LED lighting apparatus. That means that actual LED lifetime is being wasted, consequently wasting the manufacturing cost. This paper proposes a new LED drive circuit topology, which does not need any electrolytic capacitors and shows the simulation results of the circuit. Also described are simulation results of its efficiency, the power factor, and EMC characteristics without any reactance at the line interface. From the simulation results, it is shown that the circuit topology has the potential for practical use.

A high voltage and large capacity power semiconductor module has a sense-emitter terminal and emitter terminal for the gate drive. There exists a parasitic wiring inductance between the sense-emitter terminal and emitter terminal. When current flows through a module, induction voltage (differential value of module current) is generated. In this study, we develop a circuit that detects the current flowing through the module by integrating the induction voltage. The integrator has the problem of integral error. It was confirmed that this problem can be solved by adopting a method of reducing the output of the integrator during energization. Further, resistance exists in the wiring inductance. It was shown that this can be solved by using the metal-oxide-semiconductor field-effect-transistor (MOSFET). Finally, experiments were conducted using a 3300V/450A IGBT module. Through the results of the experiments, it was confirmed that the proposed circuit can detect the current and abnormal current, such as the short circuit current through a power semiconductor module.

This paper presents an approach for position sensorless control in piezoelectric actuators. To achieve high-precision positioning with a piezoelectric actuator, a feedback control system using a high-resolution position sensor should be used to mitigate nonlinearities and disturbances. Sensorless control is desirable to reduce the cost and space utilization in micro- and nano-positioning systems. In this paper, actuator position is estimated based on the capacitance of the actuator because the displacement is propotionate to the capacitance. To measure the capacitance, a reference voltage with a high frequency component is injected into the actuator. On the basis of the reference voltage and current, the capacitance is estimated through the discrete Fourier transform. The displacement of the actuator is calculated using the relationship between displacement and capacitance. The position feedback controller is designed based on the estimated displacement signal. The proposed sensorless control approach is verified by conducting experiments using a bimorph-type piezoelectric actuator.

Recently, the non-contact conveyance methods that are applied magnetic levitation techniques have been studied in many institutes. In this paper, from the view point of practical use, the authors construct a magnetic levitation system without using gap sensors which have been essential for the conventional magnetic levitation of thin steel plates. This system adopts both current sensors and Hall-effect sensors in place of the gap sensors. In addition, we consider the peculiar inductance characteristics of magnetic levitation for a thin steel plate. Moreover, we conduct the levitation, guidance, conveyance and disturbance experiments.

To date, studies on lightning surge analysis have been conducted in the various fields, and analytical methods for railway signaling systems have been also studied. However, there are pieces of equipment unique to railway telecommunication systems; accordingly it is impossible to carry out lightning surge analysis of railway telecommunication systems in consideration of railway telecommunication cables and lightning arresters by conventional analysis methods. In this paper, we propose a lightning surge analysis model for railway telecommunication systems, and validate the accuracy of the proposed analysis model by actual measurement.

A continuous arraying winding technology of rectangular wire was investigated to develop small high-power motors. A bobbin structure with projections and bumps is proposed to facilitate arraying of the rectangular wire. The proposed winding process does not require any special mechanism for wire arraying and causes no wire torsion between coils. A trial continuous arrayed rectangular wire coil's resistance was 13.7% less than that of a round wire coil. As a result, the efficiency of a motor with rectangular wire coils was estimated to be higher than that of a motor with round wire coils by 2.3% (2000 min^-1). Furthermore, a motor with continuous arrayed rectangular wire coils does not require any bus-bars.

The controller area network (CAN) is one of the major serial bus systems and is commonly used in safety- or mission-critical automotive applications. Recently, the automobile has been motorized and many power converters have been installed in it. Hence, EMI caused by power converters on CAN communication has become a serious problem. This paper deals with the study on EMI caused by a buck converter on a CAN system. The main objective is to develop a novel switching procedure of the buck converter to reduce data transmission failure of the CAN.

Our research focuses on the machine design and control for high torque and high power density electric drives with high efficiencies and low cost.