This paper presents a comparison of axial flux permanent magnet machines (AFPMs) with an electrical steel core and that with a soft magnetic composite (SMC) core. SMCs have several advantages such as low core loss and low eddy current loss. However, compared with electrical steel, SMCs have poor magnetic properties such as low flux density saturation and unsaturated relative permeability. The analysis of the electromagnetic characteristics in a wide frequency range revealed that for an AFPM using an electric steel core, the performance was excellent in a low-frequency range; however, for an AFPM using an SMC core, the performance improves with an increase in frequency. Finally, the operation area of an AFPM using an SMC core is proposed.

This paper describes the rotor design of high-speed permanent magnet (PM) synchronous motors (PMSMs) consider-ing rotor magnet and sleeve materials. The influence of four dif-ferent sleeve materials with two different PM materials on the mechanical stress of a high-speed PM rotor is presented, and the relationship between sleeve thickness and shrink fit is examined. Rotor design criteria according to rotor materials are described by an analytical method. The proposed method is validated by an actual opera-tional test at 400,000 rpm using a fabricated proto-type rotor.

This study investigates the correlation between rotor vibration and mechanical stress in ultra-high-speed permanent magnet (PM) synchronous motors; the mechanical stress generated in the PM and the rotational vibration when the PM synchronous motor rotates at high speeds were evaluated. Two PM rotors that have the same performance characteristics but different shrink fits were studied, and the vibration of these two PM rotors was analyzed. Further, to evaluate the correlation between mechanical stress and vibration, the rotor design parameters, such as sleeve thickness and shrink fit, were varied. Based on the analysis results, a real-world model was developed and an experiment was conducted to test the vibration of these two rotors; the validity of our results was verified by performing experiments.

Permanent magnet (PM)-type linear oscillating actuators (LOAs) are used in various types of equipment owing to their high efficiency, thrust density, and good control performance. However, the disadvantage of the LOA is the side force inevitably generated by the magnetic coupling structure of the stator and the PM mover. Therefore, side force reduction is essential at the design stage. This study manages the optimal side force design of a movable PM-type linear actuator using response surface methodology (RSM). Based on the Maxwell stress equation, three optimization variables were selected for the magnet shape, and experimental points were selected using the Box–Behnken design. The RSM was performed based on the results of the experimental points obtained through the finite element method. To prevent output reduction, the back electromotive force, which is directly proportional to the thrust, was selected as the constraint. The validity of the optimal design was verified through a characteristic comparison between the optimal and initial models along with experimental verification.

This paper presents an analysis of the core loss observed in the stator of a permanent magnet linear synchronous generator. Core loss is usually calculated using the classical Steinmetz equation, but it leads to erroneous results. Consequently, several researchers have proposed modified versions of this equation, taking into account the hysteresis loss, eddy current loss, and excess loss. In this paper, we calculated all loss coefficients from the Epstein test data using a curve fitting method. Moreover, we separated the rotating and alternating fields based on the time harmonics observed with changes in the magnetic flux density. In addition, we considered the 2-D and 3-D plane flux paths that cause magnetic flux leakage. Finally, the core loss of the linear machine was calculated using a modified Steinmetz equation that considers the flux path.