Myung-Hwan Yoon

Plastic Injection Molded Rotor of Concentrated Flux-Type Ferrite Magnet Motor for Dual-Clutch Transmission

Motors for dual-clutch transmission (DCT) system are required to minimize its size because of limited space on transmission. Characteristics, low cost, and high productivity are essential to DCT motor for competitiveness of mass production. Hence, concentrated flux-type ferrite magnet motor is suggested to meet the needs of DCT motor. Because concentrated flux-type permanent magnet motor has a high torque density, it is possible for ferrite magnet motor to achieve air-gap flux as high as a rare-earth magnet motor. The most important thing for the design of concentrated flux-type motor is to reduce the flux leakage. Increase in magnetic reluctance of flux leakage path is necessary to reduce the flux leakage. Accordingly, segmented rotor core is required for the size reduction of motor. In the case of segmented rotor core type, it is necessary to have complex mechanical structure to maintain circular rotor shape and fix to shaft. Since those additional structures seriously deteriorate productivity, plastic injection molding type rotor is suggested in this paper to solve the problem.

An Asymmetric Rotor Design of Interior Permanent Magnet Synchronous Motor for Improving Torque Performance

Torque ripple is necessarily generated in interior permanent magnet synchronous motors (IPMSMs) due to the non-sinusoidal distribution of flux density in the air gap and the magnetic reluctance by stator slots. This paper deals with an asymmetric rotor shape to reduce torque ripple which can make sinusoidal flux density distribution in the air gap. Meanwhile the average torque is relatively increased by the asymmetric rotor. Response surface method (RSM) is applied to find the optimum position of the permanent magnets for the IMPSM with improved torque performance. Consequently, an asymmetric structure is the result of RSM and the structure has disadvantage of a mechanical stiffness. Finally, the performance of suggested shape is verified by finite element analysis and structural analysis is conducted for the mechanical stiffness.

Torque Ripple Reduction of IPMSM Applying Asymmetric Rotor Shape Under Certain Load Condition

This paper proposes a new numerical formula and a design method to reduce the torque ripple while improving efficiency and the control performance of an interior permanent magnet synchronous motor. In previous studies, the inverse cosine function (ICF) has been used for torque ripple reduction by making the air gap flux density distribution sinusoidal under a no-load condition. However, in this paper, the advanced inverse cosine function (AICF) based on the ICF is proposed. It determines an asymmetric rotor shape for rendering the air gap flux density distribution sinusoidal, considering a certain load condition. In addition to the torque ripple reduction, lower peak values, the total harmonic distortion (THD) of the induced voltage, and a lower iron loss can be achieved by applying the AICF, compared to the other conventional methods. The lower peak value and THD of the induced voltage are important because they affect the control performance of the motor. The lower iron loss can also lead to a higher efficiency, particularly, in the high-speed region. To verify the validity of the proposed design method, the characteristics of 8-pole, 12-slot motors that have different rotor shapes are analyzed using finite element analysis and experiments.

Torque density improvement of concentrated flux-type synchronous motor for automotive application

This paper proposes alternate bridge core of the Concentrated Flux-type Synchronous Motor (CFSM) using ferrite permanent magnets for automotive chassis actuator. The advantage of this structure is the reduction of leakage flux in the rotor bridges. Therefore, torque is enhanced in the safe mechanical structure. It is analyzed under the conditions of the constant volume of the PMs as well as the constant diameter of the rotor. By using the proposed method, the improved model is designed based on the initial model fulfilling the required specifications. Finally, the torque and mechanical characteristics of the two motors are simulated through the finite element analysis (FEA).

Simple Size Determination of Permanent-Magnet Synchronous Machines

Today, performance improvements such as reducing the time response and enhancing the efficiency of the electrical motor are one of the most important challenges. In the design of a permanent-magnet (PM) motor, the variables for sizing include the shape ratio (SR), the torque per rotor volume (TRV), and the torque density (TD), and these variables are important for determining the mechanical and electrical characteristics of the motor. This study investigated the changing patterns of the motor parameters (back electromotive force, inductance, resistance, etc.) and the motor characteristics with the changes in the SR, TRV, and TD with respect to the PM synchronous motor, and sought to determine the SR and TRV values. Toward these ends, this study proceeded with the initial design of the spoke-type (flux-concentrated) PM motor. Then, the motor parameters of the initial model were calculated using finite-element analysis. Based on the motor parameters of the initial model, the changing patterns of the electrical and mechanical characteristics of the motor according to the changes in the SR, TRV, and TD were investigated. In addition, the SR, TRV, or split ratio that can enhance the mechanical characteristics and efficiency of the motor were determined and reflected in the design.

Multipolar High-Speed IPMSM Design for EV Traction Considering Mechanical Stress

The greenhouse effect is getting worse in these days. To reduce this environmental problem, emission regulation in the automotive industries became strict. Accordingly, the automotive makers started to develop the environmental friendly vehicles such as the hybrid electric vehicle (HEV) and electric vehicle (EV). In the x-EV system, electric traction motor is the most important part act as the engine of the conventional vehicle. The design trend of the electric motor for EV traction is the high-speed low-torque with the reduction gear. For this reason, high speed operating condition should be considered in the design process. In this paper, some design factor study was done, considering both the electrical performance and the mechanical stress. Using these study results and response surface method (RSM) optimum design was conducted. From the optimum designed motor, mechanical stress simulation was done considering about the 15% margin of the maximum operating speed of the electric motor. Consequently, the multi-layered interior permanent magnet motor (IPMSM) design was done fulfill the electrical performance and the not exceeding the yield strength of the electrical steel sheet consist the electrical motor.

Design and performance analysis of moving-coil type linear actuator

This paper deals with the design and analysis of a moving-coil type linear actuator which is one of the linear actuator for compressor. The design and analysis of moving-coil type model are conducted which can reduce the weight of mover by including only coils and excluding the core. In this paper, core open model which contains two teeth is used. Dynamic characteristic of actuator is analyzed by applying parameter calculated by voltage equation to consider mechanical characteristic.

Finite-Element Analysis of Local Flux Density Variation Considering PWM Current Harmonics

Large amounts of harmonics are contained in the current as the motor is driven by pulse width modulation (PWM). Significant amounts of computing time are required to compute local flux density variation considering such current harmonics. Since the amplitudes of higher harmonics are significantly smaller than that of fundamental harmonic, flux density variations due to the higher harmonics are small, and the relationship between the field strength and flux density can be assumed to be linear. When the operating point of each element is known, flux density variations for the higher harmonics can be analyzed by linear finite-element analysis (FEA). This paper suggests a method to calculate flux density variations in the iron core while taking into considering PWM current harmonics. First, the operating point solution is obtained by nonlinear FEA, second each element is linearized. Then, the flux density for the PWM current is obtained through linear FEA. Finally, the obtained results are presented and compared with nonlinear FEA results for verification.

Torque Ripple Reduction Using Torque Compensation Effect of an Asymmetric Rotor Design in IPM Motor

In this paper, torques of two motors are compared by Finite Element Analysis (FEA). One has a symmetric rotor structure and the other has an asymmetric rotor structure. The comparison shows that the asymmetric rotor structured motor has reduced torque ripple compared to the symmetric. The torque of the compared motor models was analyzed by separating into magnetic torque and reluctance torque. Through the analysis of torque component separated, it is shown that the magnetic torque and the reluctance torque compensate each other in the motor with the asymmetric structure rotor. Here “compensate” means decrementing the effect of one or more harmonics. It is shown how this compensation appears between the magnetic torque and the reluctance torque by looking into back electro motive force (emf) and the relative permeability distribution of rotor core.

Improvement in thrust force estimation of solenoid valve considering minor hysteresis loop

Solenoid valve is a very important hydraulic actuator for an automatic transmission in terms of shift quality. The same form of pressure for the clutch and the input current are required for an ideal control. However, the gap between a pressure and a current can occur which brings a delay in a transmission and a decrease in quality. This problem is caused by hysteresis phenomenon. As the ascending or descending magnetic field is applied to the solenoid, different thrust forces are generated. This paper suggests the calculation method of the thrust force considering the hysteresis phenomenon and consequently the accurate force can be obtained. Such hysteresis occurs in ferromagnetic materials, however the hysteresis phenomenon includes a minor hysteresis loop which begins with an initial magnetization curve and is generated by DC biased field density. As the core of the solenoid is ferromagnetic material, an accurate thrust force is obtained by applying the minor hysteresis loop compared to the force calcu...