• Journal of Magnetics
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• v.22 no.2
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• pp.266-274
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• 2017

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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.12
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• pp.1703-1708
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• 2015

This paper deals with the position and torque control of a toroidal type rotor which has a magnetic bearing structure. The proposed magnetic bearing structure supports the rotor by the repulsive forces of permanent magnets, and has a two degree of freedom for rotor position when the rotor is rotating. Permanent magnets and coils in the stator allow for a two degree of freedom control of the rotor position and torque generation by reacting with permanent magnets of the rotor. The executed gyro actuator has a number of poles such as five-phase permanent magnet motors and 10 stator coils for the rotor position control. In this study, the verification of the stability of the magnetic bearing was conducted using the equation of motion when the rotor was rotating, and the coil current commutation method for the position control and torque generation was studied. As a result, the feasibility of the proposed structure and control was verified by simulations of Finite Element Method (FEM) and experiments using the executed gyro actuator.

• Wind and Structures
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• v.34 no.3
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• pp.291-301
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• 2022

Although mostly used in wind turbine market, single rotor wind turbines have problems with transportation and installation costs due to their large size. In order to solve such problems, multi-rotor wind turbine is being proposed; however, light weight design of multi-rotor wind turbine is required considering the installation at offshore or deep sea. This study proposes the systematic design process of the multi-rotor wind turbine focused on its supporting structure with simultaneous consideration of static and dynamic behaviors in an ideal situation. 2D and successive 3D topology optimization process based on the density method were applied to minimize the compliance of supporting structure. To realize the conceptual design obtained by topology optimization for manufacturing feasibility, the derived 3D structure was modified to have shell structures and optimized again through parametric design using the design of experiments and the response surface method for detail design of their thicknesses and radii. The resultant structure was determined to satisfy the stress and the buckling load constraint as well as to minimize the weight and the resultant supporting structure were verified numerically.

• Fibers and Polymers
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• v.7 no.1
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• pp.66-69
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• 2006

Spandex fibers have superior stretch and elastic recovery ability. Composite yarns containing spandex are frequently used to manufacture elastic textile products and accessories. We have developed a composite yarn spinning system that produces different kinds of composite yarns containing spandex on a modified open-end rotor spinning frame. By changing the twisting parameter of composite yarns, we studied the structure and properties of rotor-spun composite yarns with spandex. The results indicate that the twisting parameter has great influence on the structure and properties of rotor-spun composite yarns with spandex. The linear density of spandex filament has influence on the properties of composite yarns too. In comparison with normal rotor-spun yarn, the appearance of composite yarns is clearer, the structure is much tighter, and the properties are improved.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.12
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• pp.156-163
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• 2010

The brushless motor is getting widely applied to the automotive component with the advantage of the high efficiency, high reliability and etc.. Most of the motor applications require the low vibration and acoustic noise. The cogging torque is the one of the main cause of the noise and vibration. The step-skewed rotor is used to reduce the cogging torque. We analyze the characteristics of the step-skewed rotor and non skewed rotor with the same stator by using 2-dimensional FEM. And then we analyze the characteristics variation according to the rotor eccentricity. The prototype is made and tested. As the results, the step-skewed rotor structure reduce the cogging torque and local radial force but it is more sensitive to rotor eccentricity.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.25 no.4
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• pp.44-51
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• 2017

An ultra light quad-rotor is utilized in various areas for military and commercial purpose. Especially, the airframe shape is designed with various airframe size, weight and purpose. In this paper, the initial airframe shape of the quad-rotor was designed and manufactured. Flight test was conducted for the quad-rotor. The design modification of airframe shape was conducted to meet design requirement. By changing design, weight of airframe structure was reduced and payloads were placed to the best position. By reinforcing ribs and reducing vehicle's legs, the durability of airframe structure was enhanced.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.555-563
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• 2001

Support dynamics are often important in rotordynamic analyses. It may well happen in real situation of machines such as centrifugal pumps or turbines operating on flexible structure. This paper presents the applications of the impedance coupling method and the improved rotor model for including the support effects on the interaction with the rotor. The impedance coupling techniques are based on the FRFs of each substructure. Its dynamic stiffness matrix can be assembled to generate the system matrix, which satisfy the constraint conditions in the connection coordinates. And, the improved rotor uses the simplified spring-mass models as support properties. The equivalent support models are directly incorporated into the finite element rotor model. To verify the suggested analytical procedures, the results are compared to those of the pump system.

• Composites Research
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• v.18 no.4
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• pp.52-58
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• 2005

A cyclocopter propelled by the cycloidal blade system, which can be described as a horizontal rotary wing, is a new concept of VTOL vehicle. In this paper, optimized structure design is carried out for the aerodynamically optimized cyclocopter rotor system. Database is obtained fer design variables such as stacking sequence (ply angles), number of plies and spar locations through MSC/NASTRAN and optimum values are determined by RSM and some other optimizing processes. For the rotor system including optimized blade and composite hub m, the maximum stress by static analysis is within the failure criteria. And the rotor system is designed for the purpose of avoiding possible dynamic instabilities by inconsistency between frequencies of rotor rotation and some low natural frequencies of rotor.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.141-147
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• 2013

Permanent magnet (PM) motors that employ rare-earth magnets containing dysprosium (Dy) are used in electric and hybrid electric vehicles. However, it is desirable to reduce the amount of Dy used since it is expensive. This study investigates the rotor structure of a PM synchronous motor with a Dy-free rare-earth magnet. Flux barrier shapes and PM thicknesses that enhance the irreversible demagnetization are investigated. In addition, a rotor structure that improves the irreversible demagnetization is proposed. We demonstrate that the proposed rotor structure without Dy improves the irreversible demagnetization.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.8
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• pp.764-772
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• 2009

In this study, fluid/structure coupled analyses have been conducted for 3-D stator and rotor configuration. Advanced computational analysis system based on computational fluid dynamics(CFD) and computational structural dynamics(CSD) has been developed in order to investigate fluid/structure responses of general stator-rotor configurations. To solve the fluid/structure coupled problems, fluid domains are modeled using the structural grid system with dynamic moving and local deforming techniques. Reynolds-averaged Navier-Stokes equations with Spalart-Allmaras(S-A) and SST ${\kappa}-{\omega}$ turbulence models are solved for unsteady flow problems. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3-D turbine blades for fluid-structure interaction(FSI) problems. Detailed fluid/structure analysis responses for stator-rotor interaction flow conditions are presented to show the physical performance and flow characteristics.