In this article, a process for reducing the electromagnetic vibration and noise by changing the shape of the stator is presented. Although the fundamental wave of the air gap magnetic flux density contributes to the average torque of the motor, other spatial harmonics which were except the fundamental wave of that cause vibration and enfeeble the output of the motor. Therefore, it is important to reduce the spatial harmonics for performance of the motor. Through the proposed process, it is possible to obtain an objective function to reduce the specific harmonics by assigning weights to each spatial harmonic. The reduction in the fundamental wave is minimized and it is possible to reduce the spatial harmonics that have an adverse impact on vibration. After the process, a model can be found that maintains the electromagnetic performance as much as possible while optimally reducing the vibration. To verify the process, the electromagnetic vibrations by a radial force of the proposed and conventional models were compared, and it was confirmed that the electromagnetic vibration of the proposed model was reduced. The validity of the analysis was proved through finite-element analysis.

Conventional electromagnetic vibration analysis methods mainly focus on the spatial harmonic components of the radial force density. Because they do not consider time harmonics, they cannot consider the frequency component of electromagnetic vibrations. Therefore, they are not suitable for optimally designing motors by considering electromagnetic vibrations. In this paper, we propose a process to analyze electromagnetic vibrations considering time harmonics as well as spatial harmonics. For the calculation of the magnitude of electromagnetic vibrations with respect to the frequency, the natural frequency of the circumferential mode was calculated by simplifying the shape of the stator core. The natural frequency increases as the order of the stator circumferential mode increases. Using the vibration equation, it was confirmed that electromagnetic vibrations decrease as the natural frequency increases. For analyzing the correlation between the vibration source and the electromagnetic vibrations, the radial force was separated into time and spatial harmonics, and the contribution of each harmonic component to the vibration was calculated. The results revealed the harmonic components that have the most significant influence on the vibrations. Then, using the proposed process, the vibration performance, as well as the electromagnetic performance, can be used as an objective function to design motors. To verify the validity of the proposed process, the vibrations of conventional and proposed motors were analyzed. Finally, a prototype was manufactured, and its vibrations were tested using the proposed process.

This paper presents the design of an ultra-high speed PM Motor/Generator driven at a rated output and speed of 10kW and 70,000 rpm, respectively, for use in an Electric-Turbo Compounding System (E-TCS). When designing the very-high speed Motor/Generator, the mechanical and structural safety of the rotor and losses that occur when the motor operates at high speed should be considered for safe operation. In this paper, the optimal design of the ultra-high speed PM motor is performed with Finite Element Analysis (FEA) and structural analysis. Especially, the electromagnetic and structural characteristics based on the sleeve material are analyzed. The optimal design for PM motor, using carbon fiber is proposed not only to reduce the eddy-current loss, which prominently occurs at very-high speed, but also to ensure its structural safety. Finally, the validity of the design method and the effectiveness of the fabricated prototype of PM motor is verified through experimental tests.

This study focused on the efficiency improvement and acoustic noise reduction of brushless DC (BLDC) motors by reducing current harmonics using a novel BLDC commutation method. To achieve these goals, we designed an improved 150° commutation method for a three-phase permanent magnet BLDC motor that can improve the current waveform. Although the 120° commutation method is generally employed for BLDC motors, an improved 150° commutation method is introduced to operate the BLDC with increased efficiency and acoustic noise similar to a brushless AC motor. This study investigated the attributes of various commutation methods, both theoretically and experimentally, to determine the optimal commutation method. The results of this study indicate that the improved 150° commutation method is optimal in terms of harmonic attributes and reduced torque ripple, allowing it to improve motor efficiency and reduce acoustic noise.

This paper establishes an analysis method of permanent magnet assistant synchronous motor (PMA SynRM) with asymmetric barrier. In a general motor analysis method, the inductance is calculated using the dq-axis vector diagram. In addition, the characteristics of the motor are analyzed by separating the mag-netic torque and the reluctance torque. However, in an asymmet-ric motor, the magnetic neutral plane (MNP) is shifted because the magnetic permeance is asymmetric. Therefore, it is difficult to analysis the characteristic of the asymmetric motor because it in-volves errors applying the general analysis method. In this paper, the magnetic property of the asymmetric motor is analyzed and the analysis method of asymmetric motor is proposed. To verify the proposed analysis method, PMA SynRM is designed as a conventional model. Furthermore, the magnetic torque and reluc-tance torque are separated through the proposed analysis meth-od. The validity of the proposed analysis method is verified through finite element analysis (FEA) and manufacture of the conventional model.

Interior permanent magnet synchronous motors have the advantage of being applicable to various fields owing to their high torque density and wide operating range but have the disadvantage of large electromagnetic vibrations. To calculate the electromagnetic vibration, analysis of the magnetic flux density of the air gap using the finite element method (FEM) is essential. This process requires a significant amount of time because of the use of many analysis models. The radial force, which is the source of vibration, is expressed as the square of the air gap magnetic flux density, the vibration can be predicted in advance by calculating the waveform of the air gap magnetic flux density using a formula. In this paper, a new air gap relative permeance formula is proposed when an offset is applied to the outer diameter of the rotor to reduce electromagnetic vibration. By calculating the waveform of the air gap magnetic flux density using the proposed air gap relative permeance formula, a model with a minimum total harmonic distortion is selected. The validity of the formula was confirmed by comparing the FEM result with the waveform of the air gap magnetic flux density calculated using the proposed formula. The proposed model minimized the vibration and was confirmed using FEM. Using the proposed formula, vibration can be easily and quickly predicted in analytic way. The prototype of the final model was developed and compared using FEM, and the validity of the analysis result was confirmed.