This paper presents a new method for calculating the braking force of a drum-type eddy current brake with a two-layer structure. The drum-type eddy current brake should have a structure that improves the braking force by applying a material with high conductivity inside the drum because the eddy current loss generated from the drum is used as the braking force. In addition, because the eddy current brake operates at various speeds while braking the vehicle, it is necessary to grasp the braking force according to the speed. Furthermore, because the material of the drum is composed of non-laminated iron having conductivity, the skin effect and the armature reaction phenomenon appear, and the skin depth and the air-gap flux density are different depending on the braking speed. In this paper, the value of the eddy current loss of the eddy current brake with a copper coating inside the drum is newly presented and compared with the finite-element analysis results. In addition, the change in the speed-torque curve according to the conductivity value of the drum and inner coating material are shown. Finally, an experiment was conducted to compare and verify the characteristic curve of the eddy current brake obtained from the newly derived equations.

This paper studies the output performance improvement of the spherical multi-degree-of-freedom (multi-DOF) motor. The multi-DOF motor is a motor that is designed to drive in multiple axes. Therefore, it is important that the shape of the motor should be fabricated to enable multi-axis driving when designing the multi-DOF motor. In addition, it is essential to consider the output density characteristics and stability characteristic analysis to reduce the volume of the multi-DOF motor and to operate of the motor in the stable range, respectively. In this paper, the structure and operating characteristics of the spherical multi-DOF motor with dual air gaps are described. In order to improve the output characteristics of the multi-DOF motor, characteristics analysis was performed according to the change of the number of the phases and pole pitch angles, and stability characteristic analysis for stable operation of the multi-DOF motor was performed.

This paper contains the results of actually applying to motor development the 3-D printing technology, which is one of noteworthy technologies to lead industries in the future. The current level of 3-D printing technology was identified, synchronous reluctance motor was designed and fabricated on the basis of the technology, and experiment was carried out to verify the design and fabrication. The comparative analysis between the existing model and the proposed model was carried out by finite element method analysis and experiment, and it shows the possibility that 3-D printing technology can be applied to the motor industry.

The spoke-type permanent magnet synchronous motor (PMSM) is a motor built using nonrare earth elements, which feature low flux density. It has a flux concentrated structure of permanent magnet arrangement to improve power density. Further, the torque in the spoke-type PMSM is composed of a magnetic torque component from the permanent magnets and a reluctance torque arising from the inductance difference between the d - and q -axis. This paper analyzed the d - and q -axes inductances that affect the reluctance torque depending on the magnitude of the applied current and the current phase angle of the spoke-type PMSM at base speed. We also derived the variation of the d - and q - axis inductances, which is shown at the operation speed region. Accordingly, the variation of the current phase angle for generating the maximum output power is analyzed. Based on the above results, we predicted the variation in the driving mode of the spoke-type PMSM, and subsequently verified the prediction experimentally.

This paper proposes a quasi-semi-closed (QSC) slot design method for an open-slot-type interior permanent magnet synchronous motor (IPMSM) for independently rotating wheelsets necessary to reduce the total harmonic distortion of no-load back-electromotive force and the torque ripple in the IPMSM. Four different slot-opening models were selected--the basic model, hairpin coil model, magnetic-wedge model, and QSC-slot model--and 2-D finite-element analysis was performed under open-circuit and load operations for each of the four models. Next, the relationships among the cogging torque, the torque ripple, and the saturation phenomenon in the core were analyzed. In addition, the manufacturing process, manufacturing cost, fill factor, end-winding resistance, copper loss, and efficiency were investigated. The experimental results verify the accuracy of the proposed method.

This study investigates the starting capability of a high-efficiency synchronous reluctance motor for direct online industrial applications. Because of structural limitations, line-start synchronous reluctance motors (LS-SynRMs) are commonly diecasted by reducing pressure to ensure safe manufacturing. Hence, the shape of the squirrel-cage bars, including bubbles and blisters in the rotors of LS-SynRM, needs to be analyzed. In this paper, three different models are proposed to model the random bubble and blister phenomena by using 2-D finite-element analysis (FEA); their impacts on the flux paths and the change in exciting current of the squirrel-cage bars due to the unbalanced bubbles are thoroughly evaluated. Finally, consider that the bubbles' impacts are confirmed by manufacturing the prototype motor and performing the experiment. The results of FEA and the experiment clearly indicate that the impacts of additional bubbles and blisters need to be considered in the design of LS-SynRMs.