• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.423-426
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• 2007

Pohang Wind Energy Research Center (PoWER-C) is developing a 3 MW Radial Flux Permanent Magnet (RFPM) Synchronous Generator for offshore Wind Energy Converter (WEC). The rotor rpm is 15.7 and the gear ratio is set to be 92.93. The nominal generator rpm at the rated load is about 1459. To reduce the switching loss in the power electronics, the maximum frequency is limited to 100 Hz. This requirement limits the number of pole to six or eight. Permanent magnet excitation is assumed for higher energy yield and higher efficiency. In this report, the requirements and the first efforts for the physics design are described.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1075-1076
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• 2011

This paper compares performance characteristics and mechanical design specifications of outer rotor radial flux type and double-sided axial flux type permanent magnet generator for 1.5-kW class small scale wind power applications to suggest most suitable type. In order to analyze electromagnetic performances of two different type generators, this paper performs generating performance and efficiency characteristic analysis from electrical parameters obtained by using nonlinear finite element analysis using commercial software, electromagnetic losses characteristics equations and d-q characteristics equation. Considering the derived electromagnetic performance, mechanical design specifications and manufacturing cost, the best suitable model for 1.5-kW class wind power system is determined, and its experiment was performed to validate the suggested analysis method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.1
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• pp.57-64
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• 2010

In this paper, a novel Bearingless Switched Reluctance Motor(BLSRM) with the shoe rotor pole in order to minimize the torque ripple and the suspension force ripple at an overlap position is proposed. For reduction the torque ripple and the suspension force ripple at an overlap position, the fringing flux is used for the main flux. This configuration of the rotor pole results in more average torque with high suspension force. In addition, this paper is compared the transient characteristics using the inductance look-up table. The torque, radial force and flux density are analyzed by finite element method.

• Journal of Magnetics
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• v.20 no.4
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• pp.360-365
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• 2015

Spatial distributions of magnetic flux density in a newly designed magnetized inductively coupled plasma (M-ICP) etcher were investigated. Radial and axial magnetic flux densities as well as the magnetic flux density on the center of the substrate holder were controllable by placing multiple circular coils around the etcher properly. The plasma density non-uniformity in M-ICP (25 Gauss) can be reduced (1.4%) compared to that in ICP (16.7%) when the neutral gas pressure was 0.67 Pa and a right-hand circularly polarized wave (R-wave) can be propagated in to the etcher by making magnetic flux density increases both radially and axially from the center of the substrate holder.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.880-887
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• 1998

In order to study heat transfer characteristics of spray cooling for the purpose of uniform and soft cooling of high temperature surface a series of experiments for a hot horizontal copper flat plate was performed by downflow spray water using flat spray nozzle. Cooling curves were mea-sured under the various experimental conditions of flow rates and temperatures of cooling water Surface temperature surface heat fluxes and heat transfer coefficients of horizontal upward-facing flat surface were calculated with cooling curves measured at each radial positions near the cooling surface by TDMA method. Generally heat transfer characteristics for spray cooling is simi-lar to boiling phenomenon of pool boiling. The minimum heat flux(MHF) appear at the surface temperature of about ${\Delta}Tsat=250^{\circ}C$ and the critical heat flux(CHF) appear at about ${\Delta}Tsat=250^{\circ}C$.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.796-797
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• 2015

This paper deals with torque analysis of magnetic cycloid gear with radial magnetized permanent magnets based on analytical method. These analytical results are validated by comparing with the 2D finite element analysis (FEA).

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.3
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• pp.5-11
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• 2003

A simulation model for radial magnetic bearings is presented. The model incorporates hysteresis, saturation and eddy current effects. A simple magnetization model that describes hysteresis and saturation is proposed. Eddy currents are taken into consideration by assuming that they are generated by single-turn fictitious coils wrapped around each magnetic flux path. The dynamic equations describing the simulation model can easily incorporate the operation of switching power amplifier. A simulation of a typical 8-pole radial magnetic bearing produces switching waveforms very similar to the experimental observation.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.122-122
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• 2012

Geosynchronous electron flux dropouts are most likely due to fast drift loss of the particles to the magnetopause (or equivalently, the "magnetopause shadowing effect"). A possible effect related to the drift loss is the radial diffusion of PSD due to gradient of PSD set by the drift loss effect at an outer L region. This possibly implies that the drift loss can affect the flux levels even inside the trapping boundary. We recently investigated the details of such diffusion process by solving the diffusion equation with a set of initial and boundary conditions set by the drift loss. Motivated by the simulation work, we have examined observationally the energy spectrum and pitch angle distribution near trapping boundary during the geosynchronous flux dropouts. For this work, we have first identified a list of geosynchronous flux dropout events for 2007-2010 from GOES satellite electron measurements and solar wind pressures observed by ACE satellite. We have then used the electron data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft measurements to investigate the particle fluxes. The five THEMIS spacecraft sufficiently cover the inner magnetospheric regions near the equatorial plane and thus provide us with data of much higher spatial resolution. In this paper, we report some case studies showing energy dependence during magnetopause shadowing effect.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.10
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• pp.959-967
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• 2012

The theory for a new electromagnetically biased diskless combined radial and axial magnetic bearing is developed. A typical magnetic bearing system is composed of two radial magnetic bearings and an axial magnetic bearing. The axial magnetic bearing with a large axial disk usually limits rotor dynamic performance and makes assembling and disassembling difficult for maintenance work. This paper proposes a novel electromagnet biased integrated radial-axial magnetic bearing without axial disk. This integrated magnetic bearing uses two axial coils to provide the bias flux to the radial and axial air gaps of the combined bearing. The axial magnetic bearing unit in this combined magnetic bearing utilizes reluctance forces developed in the non-uniform air gaps such that the axial disk can be removed from the bearing unit. The 4-pole homopolar type radial magnetic bearing unit is also designed and analyzed. Three dimensional finite element model for the bearing is also developed and analyzed to illustrate the diskless combined magnetic bearing.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.191-193
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• 1999

The various advantages of DSPSRM lie in constructional simplicity, robustness and low cost. Also it has a specific characteristic of axial flux machine and radial flux machine simultaneously. In this paper, we designed and manufactured its operating drive and measured the characteristics of torque, efficiency, current to speed.