Permanent-magnet synchronous motors (PMSMs) are used for traction application in electric vehicles (EVs) and hybrid electric vehicles (HEVs). However, PMSMs generate vibration and acoustic noise in the connected load due to torque ripple. Torque ripple reduction techniques require accurate modeling of torque ripple and estimation of motor parameters considering magnetic saturation and magnet temperature variation. Existing approaches that consider magnetic saturation and magnet temperature variation are complicated and difficult to realize. Therefore, this paper proposes a torque ripple expression which is regarded as complex vector behavior. It can easily determine the high harmonic current reference to reduce the torque ripple by geometrically expressing the torque ripple. Furthermore, the effect of the proposed method of torque ripple reduction was experimentally verified.

The frequency-shift type automatic train stop (ATS) equipment is a low-cost train control system and is used widely in domestic local railway. The frequency-shift type transmission equipment possesses special characteristics that are suitable for the location detection function by the onboard equipment, but the volume of information that can be transmitted is limited. Therefore, when developing a new train control system, the lack of volume of information has been often a problem. Here, we developed a new information transmission system that is compatible with existing equipment and increases the volume of information. This equipment achieves more than 10 times of volume of information compared to existing equipment by using the new information transmission method and new type of ground beacon. By using this onboard equipment as a means of location correction, the location of the train can be detected at a low cost. This report describes realization procedure of this equipment and the results of a production test.

This study proposes a novel magnetic circuit topology of a three-phase electromagnetic pump for use in molten aluminum lifting applications. Typically, annular linear induction type magnetic circuits are widely adopted, and they have structures wherein comb-shaped yokes are inserted into the annular coil from the outer diameter side. The proposed novel magnetic circuit employs a flux transverse structure in which the annular coil is sandwiched between both sides of claw pole iron cores. The large number of claw poles intentionally generate harmonic flux in the airgap between iron cores and work to increase an eddy current in the conductive liquid. First, the principle and advantages of the proposed circuit are described based on electromagnetic field analysis. Next, the structural design and prototype are presented. Finally, the result of the principle verification by the alternative equipment using the aluminum pipe is reported.

In recent years, the fields of use of permanent magnet synchronous motors (PMSMs) have expanded, and they are being applied in various fields. As a method for improving the variable speed range under power supply voltage restrictions, an open ended winding permanent magnet synchronous motor (OEW-PMSM) that is driven by two inverters with an open connection instead of the connection of the three phases of the motor is being researched. In this paper, we clarify the factors that cause the generation of the zero-sequence current owing to the PMSM structure and clarify the electrical and magnetic parameters of the PMSM that affect the generation of the zero-sequence current. Furthermore, we propose a feedforward decoupling controller between the dq0 axes that can be easily realized up to a high frequency by using the clarified factors and demonstrate that the proposed method can effectively suppress the zero-sequence current.

This paper describes an accurate chip thermal resistance (R_th) estimation method by the cooling effect of Reverse Conduction Insulated Gate Bipolar Transistor (RC-IGBT). The cooling effect achieved using the non-operational region of the RC-IGBT allows to estimation of the chip R_th when the IGBT and FWD (Free Wheel Diode) regions are by periodically on the device and used as the lead frame structure. A chip R_th estimation accuracy is improved by 15% compared with the conventional method. Additionally, the RC-IGBT has a 60% lower chip R_th compared with conventional IGBT or FWD. It is noted that the ratio of the FWD and IGBT regions of the RC-IGBT should be 0.26 : 1 enable optimization of the RC-IGBT of each R_th simultaneously.

This paper introduces a pulse-width modulation (PWM) method for a two-motor drive system that reduces the propagation of conduction noise to the power supply. This two-motor drive system consists of two motors with two inverters, each of which are connected to a common DC bus. The proposed method suppresses the common mode voltage ideally to zero by shifting the rise and fall times of the output voltage of each inverter. Our experimental results show that the rise and fall times of the output voltage can be synchronized even when the two inverters are driven at different amplitudes and frequencies. We confirm that the proposed method suppresses the propagation of conduction noise to the power supply.

Multiport converters (MPCs) that integrate multiple converters into a single unit have been proposed to reduce the converter count in electric vehicle power systems where multiple batteries are employed. However, conventional MPCs comprising a dual active bridge (DAB) converter and an interleaved PWM converter require feedback control loops and current sensors to balance the inductor currents. Furthermore, the transformer utilization decreases as the duty cycle of the interleaved PWM converter drifts away from 0.5. This paper proposes a novel MPC that integrates a DAB converter and an interleaved PWM converter with an automatic current balancing capability and improved transformer utilization. A 1-kW prototype with a half-bridge or full-bridge circuit on the high-voltage side was built for the experimental verification, and loss analysis was performed. The results demonstrated the automatic current balancing capability, improved transformer utilization, and flexible power exchange among three ports.

The objective of this study is the discussion of a simple calculation method for the magnetic reluctance and self-inductance of electromagnets with a wide air gap. Generally, the self-inductance of electromagnets with an air gap is calculated by the magnetic circuit theorem. However, it is difficult to calculate the reluctance of wide air-gaps because the magnetic flux spread cannot be ignored. In this study, the authors propose a simple calculation method for the magnetic reluctance of wide air gaps using the Nagaoka coefficient and investigate the self-inductance of electromagnets with a wide air gap using the magnetic circuit theorem. The proposed model was tested in comparison to the experimentally measured self-inductance of the test electromagnet. The results showed that the proposed calculation method can be used in the engineering design of electromagnets with a wide air gap.

In this paper, a new type of axial gap motor, named the “flux-modulating hybrid-field consequent pole motor (FHCM)”, is proposed. To enable flux modulation, the FHCM comprises rotor iron pieces sandwiched between two stators, the armature, and field poles. The field poles comprise permanent magnet poles, iron poles, and ring field windings. The magnetic flux of the field poles can be adjusted by varying the field current. The electromagnetic performance of the FHCM, including the air-gap magnetic flux density, back-electromotive force, torque, and torque ripple, was theoretically analyzed, and the results were verified through three-dimensional finite element analysis and experiments. By utilizing the inner space of the machine, the proposed FHCM could achieve a higher torque density than that of the conventional flux-modulating hybrid field motor.

Wireless power transfer systems are presently being studied as a charging method for electric vehicles. There is a problem that system is large size since conventional systems require a DCDC converter to regulate the load voltage for high efficiency. The proposed system uses three-phase winding of an open-end winding motor as the reactor for the DCDC converter during charging mode, and the inverter on one side is used as a rectifier circuit and converter switch. Thus, we can reduce the size of the wireless power transfer system and improve its efficiency.