Hyun-Soo Seol

Current Control of WRSM Considering Magnetic Saturation Phenomenon

This paper introduces the characteristics of a 120 kW class wound rotor synchronous motor (WRSM) considering the effects of magnetic saturation in electrical steel. The flux linkage due to the rotor windings and the d-axis inductance of WRSM vary non-linearly because of the magnetic saturation. This affects the selection of a current combination for maximum torque per ampere (MTPA) control. The relation between the current combination for MTPA control and magnetic saturation is analyzed in this paper. Finding a current combination that satisfies the requirements is very difficult, because WRSM has complicated current combinations (i f , id, and iq). Therefore, an algorithm for the calculation of the optimal current is proposed using the Lagrange function, and the current map is presented. Finally, the validation of the selected current combination is performed through the comparison of the results of an experiment and the finite-element analysis.

Design of Winding Changeable BLDC Motor Considering Demagnetization in Winding Change Section

In this paper, a changeable winding brushless DC (BLDC) motor for the expansion of the speed region is described. The changeable winding BLDC motor is driven by a large number of phase turns at low speeds and by a reduced number of turns at high speeds. For this reason, the section where the winding changes is very important. Ideally, the time at which the windings are to be converted should be same as the time at which the voltage changes. However, if this timing is not exactly synchronized, a large current is generated in the motor, and the demagnetization of the permanent magnet occurs. In addition, a large torque ripple is produced. In this paper, we describe the demagnetization of the permanent magnet in a fault situation when the windings change, and we suggest a design process to solve this problem.

Decrease torque ripple for SynRM using barrier arrangement design

SynRM (Synchronous Reluctance Motor) is a high efficient motor with simple structure and lower price than induction motor. However, the torque ripple of Synchronous Reluctance Motor is very large. This paper analyzes the SynRM output characteristics with a new rotor flux barriers arrangement design. And the stator of SynRM is as similar as an induction motor. A method for reducing the torque ripple is described by designed the relative positions between outer edges of flux barriers and slots correspond. Then, devised several new models and compared with a basic model. As a result torque ripple can be reduced.

Optimal Design Strategy for Improved Operation of IPM BLDC Motors With Low-Resolution Hall Sensors

This study proposes an interior permanent magnet (IPM) brushless dc (BLDC) motor design strategy that utilizes BLDC control based on Hall sensor signals. The magnetic flux of IPM motors varies according to the rotor position and abnormal Hall sensor problems are related to magnetic flux. To find the cause of the abnormality in the Hall sensors, an analysis of the magnetic flux density at the Hall sensor position by finite element analysis is conducted. In addition, an IPM model with a notch structure is proposed to solve abnormal Hall sensor problems and its magnetic equivalent circuit (MEC) model is derived. Based on the MEC model, an optimal rotor design method is proposed and the final model is derived. However, the Hall sensor signal achieved from the optimal rotor is not perfect. To improve the accuracy of the BLDC motor control, a rotor position estimation method is proposed. Finally, experiments are performed to evaluate the performance of the proposed IPM-type BLDC motor and the Hall sensor compensation method.

Design of 3-Times Magnetizer and Rotor of Spoke-Type PMSM Considering Post-Assembly Magnetization

Unlike the existing bar-type permanent magnets, it is difficult to magnetize the ferrite spoke-type permanent magnet synchronous motor (PMSM), because the permanent magnet is placed deep inside the shaft. In order to magnetize permanent magnet, a high magnetic field intensity is required. However, the high magnetic field intensity may cause demagnetization of surrounding permanent magnets. It has a bad effect on the magnetization of the permanent magnet and the performance of the spoke-type PMSM. In this paper, we proposed magnetizer models for magnetization of spoke-type 10 pole rotor and the inter-pole winding to reduce the demagnetization of surrounding permanent magnets. Finally, the optimally designed model was manufactured and the performance of the magnetizer was verified.

Effect of Pole–Slot Combination on Eddy-Current Formation in PMSM Rotor Assembly Including Retaining Plate Structure

The results of the 3-D finite-element method electromagnetic analysis of the constant speed variable output permanent magnet synchronous motor including the rotor retaining plate structure confirmed that the eddy current flow was induced in the rotor part. Eddy current flows from the permanent magnet to the rotor retaining plate, and it was found that there is induced voltage that generates eddy currents in the retaining plate from the aspect of eddy-current distribution. The eddy current flow from the permanent magnet to the retaining plate is related to the change in magnetic resistance during rotation and is also related to the effect of slot harmonics on the air-gap magnetic flux density. In this paper, the characteristics of the eddy current flow in the rotor assembly were investigated when the retaining plate is included for various slot combinations. The eddy-current generation according to the slot combination is analyzed and the cause of such tendency was investigated. Furthermore, from the pattern of eddy-current formation, it was noted that the aperiodic pole–slot combination models may have a larger eddy-current loss increase when combined with the retaining plate.

Optimization of Vibration and Noise Characteristics of Skewed Permanent Brushless Direct Current Motor

In this paper, we analyze the vibration and noise characteristics of the basic and skewed models of permanent brushless direct current (BLDC) motor. The electromagnetic characteristics of the basic model are analyzed by the finite-element method. We analyzed the electromagnetic characteristics for skew angles from 15° to 25°. The skew angle was selected based on the analytical results of the electromagnetic characteristics. We analyzed the characteristics of radial force density for the basic model and the skewed model. The vibration and noise characteristics were analyzed through the mechanical harmonic analysis of the radial force and tangential force generated in the motor. We developed the basic and skewed models, and performed vibration and noise tests. The validity of this analysis is verified by comparing the simulation results with the actual test results of the model. Finally, for the optimal design of the BLDC motor considering vibration, the design variables such as teeth shoe length, yoke thickness, and teeth thickness were used. Based on the results of vibration analysis, the final model is derived and its performance is described.

Characteristic analysis of Spoke-type IPMSM corresponding to the rib structure

In order that Spoke-type interior permanent magnet synchronous motor (IPMSM) can operate in high speed region, field weakening control is required. Also, the rotor should be mechanically robust for the reliability. Structurally, Spoke-type IPMSM can have the rib on the outermost of rotor. The rib helps extend operation range and prevent the scattering of permanent magnet and pole pieces in high speed operation. Also, it can affect the permanent magnet demagnetization. So in this paper, the effect of rib on the operation range, mechanical stress and permanent magnet demagnetization is analyzed. Finally, effect of rib thickness is analyzed and relation to high speed operation is presented.