In general, permanent magnet (PM) motors are driven by a pulse width modulation (PWM) voltage source inverter for vector control. The generated PWM signals cause high-frequency voltage components at the carrier frequency. Such components can increase the electromagnetic losses, thereby necessitating the consideration of the phase current corresponding to the carrier harmonics. This study aims to examine the feasibility of high-speed permanent magnet (PM) motors in which rare-earth magnets are replaced by ferrite magnets, by considering the current harmonics. The electromagnetic characteristics of a high-speed motor with rare-earth and ferrite PMs were analyzed considering the current harmonics. Based on the existing rare-earth magnet model, a ferrite magnet model with the same performance was developed to perform a comparative analysis. The findings were validated via comparison with the experimental results of the manufactured models.

This study presents an approach to calculating the temperature increase in the internal components of permanent magnet synchronous machines by applying lumped-parameter thermal networks and analytical methods. Accordingly, the thermal equivalent circuit method is employed to obtain the temperatures of the machine’s internal components. Furthermore, this analytical method predicts the temperature distribution in the slot area. The 24/6 prototype was used to evaluate the proposed model by comparing the calculated and finite element method simulation.

This study proposes a semi three-dimensional analysis method for a permanent magnet linear device with a radially laminated structure. After the magnetic flux density was calculated using two-dimensional finite element (FE) analysis, the magnetic flux density in the iron core was estimated by considering the volume of the divided core. Finally, a core loss analysis of the laminated core was performed using the modified Steinmetz equation, and the results was compared with the FEM analysis results. Additionally based on the predicted magnetic flux density, the electromagnetic characteristics were compared through the experiment.

In general, high-speed machines should be designed to satisfy electromagnetic and mechanical characteristics. In this study, the design of high-speed permanent magnet synchronous generator with two different shaft materials considering overhang effect and mechanical characteristics was performed. It was confirmed that the leakage magnetic flux generated by the two shaft materials electromagnetically affects the high-speed generator. Additionally, it is important to accurately predict the natural frequency mode and critical speed to prevent damage and vibration of the rotating body owing to scattering during high-speed rotation. Therefore, the mechanical characteristics of the designed model were analyzed. In this study, we propose a design method that considers both the electromagnetic effects and mechanical characteristics. Subsequently, verification was performed through experiments and comparisons for the validity and reliability of the proposed design method.

In this study, we performed the electromagnetic and mechanical characteristic analyses of an 8-pole 12-slot interior permanent magnet synchronous motor (IPMSM). Permanent magnet synchronous motors are classified into surface permanent magnet synchronous motor and interior permanent magnet synchronous motors according to the type of rotor. The IPM type is advantageous for high-speed operation because of the structure where the permanent magnet is embedded inside the rotor, and it has the advantage of having a high output density by generating not only the magnetic torque of the permanent magnet, but also the reluctance torque. However, such a motor has more vibration/noise sources than other types, owing to changes in reluctance. The sources of motor noise/vibration can be broadly classified into electromagnetic, mechanical, and aerodynamic sources. Electromagnetic noise sources are classified into electromagnetic excitation sources, torque pulsations, and unbalanced magnetic forces (UMFs). Vibration and noise cause machine malfunctions and affect the entire system. Therefore, it is important to analyze the electromagnetic vibration source. In this study, the electromagnetic characteristics of an IPMSM were analyzed through the finite element method to derive the UMF. Vibration and noise analyses were performed by electromagnetic–mechanical coupling analysis, and vibration and noise characteristics based on electromagnetic noise sources were analyzed.

This paper presents the design for a high-speed permanent magnet synchronous machine (PMSMs) considering the demagnetization and mechanical characteristics of rare-earth magnets based on the operating temperature. The TRV equation and plane stress analytical method are considered for the temperature, the rotor size is derived from the analysis results of the sleeve thickness, and the stator is designed on the basis of the results of the electromagnetic analysis method. The B–H curve of the permanent magnet (PM) changes with its operating temperature; thus, a thermal demagnetization analysis is conducted to verify the irreversible demagnetization caused by the operating temperature and armature reaction field using electromagnetic finite element method (FEM). It is necessary to consider the irreversible demagnetization with the operating temperature because it can decrease the electromagnetic performance. Therefore, the electromagnetic characteristics of high-speed machines using rare-earth PMs are analyzed to confirm irreversible demagnetization. The validity of the proposed design is confirmed via comparative verifications with the measured results from prototype models.