Masahiro Aoyama

For electric micromobility applications, an axial-length shortening is required for the coil winding area of the distributed winding stator. In addition, an integrated motor drive (IMD) system is desirable to achieve miniaturization, unitization, and improved efficiency of the motor drive systems. In this study, a new IMD system is proposed in which the coil-end of the distributed winding stator is replaced with a printed circuit board (PCB) and the drive circuit is integrated in that area. First, the proposed motor structure and prototype have been revealed. At the current stage, the coil-end PCB and the drive circuit PCB have been designed to be the same for integration, but they are separate boards. The drive characteristics of each individual component were evaluated and have been clarified. Additionally, the evaluation results of system efficiency and losses when these components are placed in spatial proximity have been presented.

In this paper, a double axial gap type induction motor having a toroidal winding stator structure is proposed for the purpose of improving the torque density and efficiency of the induction machine. It consists of an axial type squirrel-cage induction rotor, and a toroidal winding stator structure suitable for armature copper loss reduction, miniaturization and a double axial gap structure. After explaining the reasons for selecting the single stator and double rotor structures, the structural design of the prototype and the experimental setup will be reported. The slip-vs.-torque characteristics are measured to clarify the drive characteristics, and the features of the proposed motor used soft magnetic composites are discussed by the equivalent circuit method. As a result, it was experimentally clarified that the double axial gap type induction motor with soft magnetic composites has a high slip torque characteristic and the reduction of the excitation current is an important issue for improving the performance.

In this paper, consideration from the viewpoint of the dq -axis current vector locus is reported on the clues for improving the output of wound-field motor utilizing space harmonic for field excitation. It is experimentally verified by visualizing the vector locus on the dq coordinates. First, voltage equation will be explained, and then the offline parameter estimation will be discussed. Then, visualization of the voltage-limit ellipse and vector locus will reveal clues for performance improvement.

This paper proposes a new induction heating (IH) coil using Halbach-arranged coils for cooktop. In general, a control inverter is placed on the back side of the coil, but by using the Halbach array coils, magnetic flux leakage to the back of the coil can be prevented without using a ferrite cores for magnetic shielding. Further, the magnetic flux can be concentratedly linked to the pot. First, differences and advantages of the magnetic flux distribution between the conventional IH-coil and the proposed IH-coil will be described based on electromagnetic field analysis. Next, the results of verification of the effect of the Halbach array coil via the prototype for principle verification are demonstrated.

This study clarifies experimentally the effect of the secondary conductor bar on line‐start characteristics in a line‐start type self‐excited wound‐field synchronous motor. This motor is based on a brushless wound‐field synchronous motor having a rotor winding connected to a diode rectifier circuit. And it has a secondary conductor bar that is independently connected at a pitch of one pole, without end‐ring. First, the operation principle of the proposed motor and its magnetic circuit design are described, and then the details of the prototype for principle verification are clarified. Next, when the combination of the connecting of the secondary conductor bar is changed, an experiment of line‐starting characteristics and measured rotor field current is demonstrated. Consequently, it was clarified that the influence on the synchronous pull‐in, speed ripple, and rotor field current.

This paper describes a novel line-start type self-excited wound-field synchronous motor with three-phase concentrated winding stator. The unique feature of this proposed motor is that it accelerates by obtaining the starting torque from the slip frequency at the time of starting, and at the time of synchronous pull-in, it is driven synchronously with utilizing the second order space harmonic as the field magnetization power. This driving principle was verified by performing a load test using the prototype with two types of load, fan and eddy current brake. Consequently, the synchronization based on the proposed drive principle could be demonstrated on the actual machine, and the line-start characteristics of the proposed motor have been clarified.

This paper describes a novel line-start type self-excited wound-field synchronous motor with three-phase concentrated winding stator. The unique feature of this proposed motor is that it accelerates by obtaining the induction torque from the slip frequency at the time of starting, and at the time of synchronous pull-in, it is driven synchronously with the second order space harmonic as the field magnetization power. First, the operation principle and the magnetic circuit design topologies will be described. Then, the prototype for principle verification and experimental setup will be revealed. Next, the result of evaluating the no-load synchronization pull-in characteristics is demonstrated.

This paper describes a permanent-magnet-free synchronous motor where space harmonic power is utilized for the field magnetization instead of permanent magnets. The stator has a three-phase concentrated winding structure, and the rotor has two types of windings, i.e., an induction coil that retrieves mainly the second space harmonic and a field coil for the field magnetization. The two coils are connected via a center-tapped full bridge diode rectifying circuit. The principle of self-excitation utilizing space harmonics power is conducted, and the mathematical model is discussed. In addition, experimental test results are demonstrated compared with interior-permanent-magnet synchronous motor for HEV application.

It is well know that initial imperfections (e.g. bow-shaped imperfection of member, bow-shaped imperfection of plate and residual stress) have an influence on the performance of the columns. Most studies regarding this issue are investigated under single axial load or single shear force. In reality, the columns of steel structures are subjected to axial load and bending moment. Therefore, it is necessary to clarify the influence of the initial imperfections under combined loading. The influences of initial imperfections on the performance of square steel tubular columns under compressive axial force with one end monotonic bending moment were investigated by means of FEM in our previous study. As mentioned before, the columns of steel structures are subjected to axial load and bending moment, and the moment diagram is antisymmetric bending moment distribution or bending moment distribution close to antisymmetric. Therefore, it is not enough to clarify one end bending moment distribution. Also, in the previous study, the influence of the residual stress in the circumferential direction was not considered despite it exists in the member. In this study, the influences of initial imperfection on the performance of the square steel tubular column which is subjected to a compressive axial force with monotonic antisymmetric bending moment are investigated. The bow-shaped imperfection of the member (global imperfection) and continuous bow-shaped of the plate (local imperfection) are selected as geometrical initial imperfections and these imperfections are described by trigonometric function to reproduce easily. The residual stress in the longitudinal direction and the residual stress in the circumferential direction are selected as material initial imperfections. Firstly, the influence of initial imperfection on the performance and on the elastic-plastic behavor is investigated individually. Secondly, the influence of combined initial imperfections on the performance of the columns and on the elasto-plastic behavor is investigated; comparison between the experimental results are shown. Firstly, followings were found from the analysis results where initial imperfection is introduced in the member individually. 1) When the ultimate state was determined by local buckling, the global initial imperfection had a small impact on the performance. When the ultimate state was determined by bending deformation in in-plane, the direction of global imperfection had an impact on the performance as well its amplitude. 2) The amplitude of the local imperfection had a great impact on the performance of the columns. The maximum bending moment and the deformation capacity significantly decreased when its maximum amplitude exceeded 10% of permissible deviation. 3) When the ultimate state was determined by bending deformation, the plastic deformation capacity decreased with the increase of the amplitude of the residual stress in the longitudinal direction; initial stiffiness gradually decreased with the increace of its magnitude. 4) Regardless of the ultimate states, with the increase of the amplitude of the residual stress in the circumferential direction, the maximum bending moment and plastic deformation capacity decreased. Secondly, followings were found from the analysis results, where combined initial imperfections are introduced in the member. 5) In comparison with analysis results which were introduced the initial imperfection individually, the influence of the combination of initial imperfections on the variation trend of the performance was not confirmed. The local imperfection had the most significant influence on the perfomance in the imperfections that are considered in this study. 6) Validation of the numerical simulation was also performed; initial imperfections that could simulate test results in reasonable accuracy was shown.

This paper presents a variable magnetic flux PM motor in which space harmonic power is utilized for weakening the magnetic flux, automatically. The stator has a toroidally-concentrated winding structure, and the torque generation surfaces are composed of three air-gaps, including one single radial gap and two axial gaps. The radial-gap rotor is a constant-magnetized PM rotor and the axial-gap rotors are self-excited wound-field rotors. These rotors are coaxially fastened with opposite magnetic pole positions. The magnetomotive force of axial-gap rotor can automatically retrieve space harmonic power, which is inevitably generated by the concentrated winding structure. In this study, the effect of relative angle of the magnetic pole between the radial-gap rotor and the axial-gap rotors on the drive performance, e.g., current phase-vs.-torque characteristics, adjustable speed drive characteristics, and variable-magnetic-flux range, are experimentally demonstrated with a prototype machine.