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From the constant-speed variable-output motor driving test result of an interior permanent-magnet synchronous motor for a pump drive, we observed that there was an additional loss factor, which was not previously considered. Furthermore, a 3-D finite-element method analysis was performed to investigate the cause of the additional electromagnetic loss. Accordingly, it was confirmed that there was an additional eddy-current loss in the rotor retaining plate structure for the rotor assembly. Using the shape of the eddy-current path in the plate, it was determined that the eddy current was formed inside the plate itself by the bypassing magnetic flux from the permanent magnet and the slot harmonics. It was confirmed that the eddy-current path can be changed according to the structure of the plate, and the optimal retaining plate design that satisfies the design constraints was derived via the topology optimization method. Finally, the retaining plate design with the 3-D barrier structure was derived by arranging the void shape considering the total eddy-current path. Using the actual model test results, it was verified that the new retaining plate design was effective for loss reduction compared to the conventional structure.

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.

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.

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.

This paper proposed a new real-time parameter tracking algorithm. Unlike the convenience algorithms, the proposed real-time parameter tracking algorithm can estimate parameters through three-phase voltage and electric current without coordination transformation, and does not need information on magnetic flux. Therefore, it can estimate parameters regardless of the change according to operation point and cross-saturation effect. In addition, as the quasi-real-time parameter tracking technique can estimate parameters through the four fundamental arithmetic operations instead of complicated algorithms such as numerical value analysis technique and observer design, it can be applied to low-performance DSP. In this paper, a new real-time parameter tracking algorithm is derived from three phase equation. The validity and usefulness of the proposed inductance estimation technique is verified by simulation and experimental results.

This paper suggests the new PMSM design that can reduce leakage magnetic flux. Through adapting non-magnetic frame structure, it decreases leakage magnetic flux on the rotor’s rib and web structure. And with this, it increases power density of the motor. To verify the effectiveness of the new design of rotor compared to the common type, through small sized real model’s test was conducted. To obtain final model, structural FEM analysis was also used for structural stability. Additional loss generation problem that can occur in the new frame structure was checked with the 3D FEM analysis.

In this paper, 110kW high output density, high efficiency Permanent Magnet Synchronous Motor which can be applied on tram’s traction system is introduced, along with its output and loss characteristics. The motor model is 2pole 18slot model and its size has been reduced through the high speed for high output density. Especially, structure and retainer sleeve structure is applied to its structure, which is also appropriate for high speed rotation. This kind of structure has eddy current loss problem on the surface of rotor, which must be reduced for high output density design. This study has designed the most optimized additional design parameter in order to improve the output characteristics and efficiency of previous produced 2pole 18 slot 110kW motor model and how the width of airgap affects from the loss perspective is mainly analyzed. Finally, the analysis on the extent of the efficiency improvement effect compared to the previous model has performed through electromagnetic FEM analysis. The influence of airgap flux density distribution has also been thoroughly examined.

In the case of designing high-speed surface-mounted permanent magnet synchronous motor (SPMSM), the rotor retaining sleeve is inserted into the rotor to prevent the permanent magnet’s damage. It is quite an efficient way to consider manufacturability, but the sleeve becomes the major source of ohm loss in high-speed operation. In this paper, the high-speed motor for a turbo blower at the rating of 100 kW, 20000 r/min was introduced. To improve its efficiency, the retaining sleeve’s optimal design was needed. For this, parametric analysis on the shape of the retaining sleeve was carried out in a different type of motor. Within a range that meets the mechanical safety, sleeve designs have been changed. The effect of changing design variables of the sleeve was studied. This paper presents the optimized sleeve’s advantages in electrical efficiency from the results of the electromagnetic finite element analysis software. Finally, it suggests the optimal sleeve design to reduce eddy-current loss, which is related to motor shape.

This study confirmed that unexpected additional eddy current loss may occur in rotor's retaining plate, which is commonly applied to the Permanent Magnet Synchronous Motor(PMSM) rotor structure. In the study, it performs a comparison between the analysis value and the test value of the variable output PMSM motor's efficiency characteristic according to output power. In the process, it is inferred through the test result comparison that there is not considered no-load loss. Through 3D FEM analysis, additional loss generation by interaction of leakage magnetic flux and slot harmonics was confirmed. Furthermore, improved loss reduction model was derived and validated by a test model.

The super-hydrophilic amorphous titanium dioxide (TiO2) thin film was prepared by plasma-enhanced chemical vapor deposition (PECVD) process for an application to dehumidifying finned-tube heat exchangers. The chemical components and surface structure were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscope (SEM). The wettability and long-term durability were investigated by measuring the water contact angle and by performing wet/dry cycles. The samples were subjected to 1000 times of wet/dry cycles to establish long-term durability. The water contact angle of the amorphous TiO2 thin film was about 8° at as-deposited film with O2 plasma treatment and was about 15° after 1000 wet/dry cycles. The amorphous TiO2 thin film had excellent wettability and long-term durability under full wetting conditions.

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.