Sung Hong Won

A Study on the Optimal Design of SynRM for the High Torque and Power Factor

This paper presents the optimal design method of synchronous reluctance motor (SynRM) for the high torque and power factor. It is difficult to design optimal barrier shape of rotor by analytical method because of leakage flux between barriers and saturation in the core. Therefore, the optimal design of SynRM including rotor structure is proposed in this paper by using finite element method (FEM) and simulation design of experiment (DOE). Finally, the characteristics of optimal model are compared with those of the worst one

Windage Loss Reduction of High-Speed SRM Using Rotor Magnetic Saturation

This paper presents a new approach to reduce windage loss of switched reluctance motor (SRM) by changing the rotor shape. To predict the performance of improved SRM rotor, the parametric finite element analyses are needed to get inductance profiles of the proposed rotor shape. The calculated values are compared with the measurement values, in order to evaluate a validity of the proposed method.

Analysis of exterior-rotor BLDC motor considering the eddy current effect in the rotor steel shell

This paper describes the effect of eddy currents generated in the rotor steel shell of an exterior-rotor type permanent magnet brushless DC motor of which the rotor is revolving at a high speed. A two dimensional time-stepped finite element method is used to analyze the electromagnetic field and compute motor performance. The conductivity of the rotor steel shell is modified to consider the transverse edge effect. As a result, the effect of eddy currents is shown by comparing the analysis results between when the proposed method is used and when the method it is not.

Analysis of the Torque Characteristics of a Multi-Degrees of Freedom Surface Permanent-Magnet Motor

The multi-degrees of freedom surface permanent-magnet motor (Multi-D.O.F. SPM) has several degrees of freedom operations that are defined as the “roll”, “yaw”, and “pitch”. Normally, the torque that is generated to rotate a rotor includes ripples. The analysis of the torque ripples is important for improving motor performance. In terms of the electric analysis, torque ripple occurs as a result of many factors, including the rotor and stator structures, the distribution of the air-gap flux density, and the waveform of the current in the coils. In particular, the torque ripple is an important factor in the stable operation of the Multi-D.O.F. SPM. Therefore, in this work, the torque ripple was analyzed using various types of magnetization for the permanent magnet. An improved model was proposed for the Multi-D.O.F. SPM based on this analysis.

Influence on brushless DC motor performance due to unsymmetric magnetization distribution in permanent magnet

The real brushless DC motor has different permanent magnet pole magnetization levels due to the influence of the magnetizer geometry. Therefore, this paper discusses the influence of change in the magnetic parameter on brushless DC motor performances. As a result, the unbalanced magnetic force acting on the rotor, cogging torque and torque ripple are examined for spindle motor with unsymmetric magnetization distribution.

BLDC spindle motor cogging torque calculation with the moving material method in the finite element method

Instead of the moving band method, which is widely used when someone wants to perform a FEM calculation considering the rotation, a novel moving material method was proposed that makes the demand of HDD memory capacity smaller and the calculation time faster not by changing the mesh but by rotating the material properties in the magnet area. These results are especially useful to researchers who try to analyze the BLDC spindle motor considering the rotation of the outer rotor comprising a ring magnet and a back-yoke.

Motion transient analysis of flat-type vibration motor for mobile phone

The flat-type vibration motor has an axial-gap structure. Analyzing axial-gap motors with the two-dimensional (2-D) finite-element method is very difficult because we have to define the analysis surface as a cylindrical surface. In order to simulate the flat-type vibration motor, we have developed new equations of calculation for the torque of the motor, which is uses a 2-D grid model. We have measured the load torque of the vibration motor which is used for the motion transient analysis. The simulated vibration characteristic is compared with experimental value

Design Consideration of Back-EMF Constant for 3-D.O.F. Spherical PM Motor

A 3-D.O.F. spherical PM motor has 3 degrees of freedom in its motion by tilting and rotating of a shaft, which can be applied in a range of fields. The back-EMF is proportional to the field flux and angular velocity. The back-EMF constant in conventional rotating machine has a uniform value. However, in a spherical PM motor, the back-EMF constant of the coils varies according to the tilting conditions regardless of whether the angular speed is constant. Consideration of the back-EMF constant is useful for designing 3-D.O.F. spherical PM motors. In this study, the back-EMF constant of the spherical PM motor was considered carefully.

Axial-Gap Type Permanent Magnet Motor Modeling for Transient Analysis

Researchers who study axial-gap type permanent magnet motors often have difficulties in analyzing the motor because the motor structure makes it difficult to define the two-dimensional (2D) finite-element model surfaces. Sometimes they try to define the surface as a cylindrical cutting surface with appropriate assumptions and sometimes they prefer three-dimensional (3D) finite-element simulations. However, the 2D analysis of the axial-gap type motor is restricted to a specified model and it is difficult to consider winding coil shape perfectly in most cases, and the 3D simulations take too long to achieve the desired results. This paper concerns the axial-gap type permanent magnet motor modeling method which can perform the transient simulation with one static 3D finite-element simulation and a winding coil mesh. This model can shorten the simulation time dramatically. To verify the feasibility, a 2phase/4phase vibration motor transient simulation was carried out and the results are well matched with the measured ones.

Torque Calculation Method of Spherical Robotic Wrist Motor

This paper presents the torque calculation method of a new spherical robotic wrist motor capable of three degrees of freedom (DOF) motion in a single joint. The spherical motor bases its operation principle on permanent magnet BLDC motor. Prediction of the spherical motor characteristics requires the computation of the exact motor dynamics at each position and angle using 3D finite element analysis which imposes a computational burden. By only calculating Lorentz forces of the coil area mesh elements, this computational burden can be reduced