• Title/Summary/Keyword: thermal losses

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Analysis of the Cooling System for Traction Motors of the High-Speed EMU (동력분산형 고속 전철의 견인전동기 냉각 시스템 해석 및 설계기술 연구)

  • Seo, Jang-Ho;Lee, Sang-Yub;Jung, Hyun-Kyo
    • Proceedings of the KSR Conference
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    • 2008.06a
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    • pp.1188-1194
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    • 2008
  • To cope with the demagnetization risk of permanent magnets used in Interior Permanent Magnet Synchronous Motors(IPMSM), an accurate iron analysis and thermal analysis are very important. In this research, to calculate thermal increment of IPMSM for high-speed traction motor, we will extract losses of IPMSM considering the condition of field weakening control. Then we will input the calculated losses such as iron loss and copper loss as the thermal sources. Based on magnetic filed and thermal analysis, we will support the design of IPMSM for high-speed train.

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Numerical Analysis of Heat Transfer in Multichannel Volumetric Solar Receivers (다채널 체적식 태양열 흡수기에서 열전달 수치해석)

  • Lee, Hyun-Jin;Kim, Jong-Kyu;Lee, Sang-Nam;Kang, Yong-Heack
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.12
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    • pp.1383-1389
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    • 2011
  • The current study focuses on the consistent analysis of heat transfer in multichannel volumetric solar receivers used for concentrating solar power. Changes in the properties of the absorbing material and channel dimensions are considered in an optical model based on the Monte Carlo ray-tracing method and in a one-dimensional heat transfer model that includes conduction, convection, and radiation. The optical model results show that most of the solar radiation energy is absorbed within a very small channel length of around 15 mm because of the large length-to-radius ratio. Classification of radiation losses reveals that at low absorptivity, increased reflection losses cause reduction of the receiver efficiency, notwithstanding the decrease in the emission loss. As the average temperature increases because of the large channel radius or small mass flow rate, both emission and reflection losses increase but the effect of emission losses prevails.

Thermal Losses Due to Non-ideal Gas Behavior of Helium in VM Heat Pumps (헬륨의 비이상기체 거동에 따른 VM열펌프의 손실)

  • Baik, J.H.;Chang, H.M.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.8 no.2
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    • pp.279-287
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    • 1996
  • A cycle analysis is performed to investigate how the non-ideal gas behavior of helium reduces the heating capacity of VM heat pumps. Since the operating pressures of VM heat pumps are as high as 1 to 20 MPa, the compressibility factor of helium becomes clearly greater than 1 and the non-ideal behavior always represents a thermal loss in heating. To calculate the amount of the losses, an adiabatic cycle analysis is performed with the real properties of helium and the net enthaply flows through the two regenerators are numerically obtained. It is shown that the non-ideal gas losses could be as much as 8% in the heating capacity when the operating pressures are greater than 10MPa. The effects of the operating temperatures and the dead volumes on the loss are presented.

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Loss Analyses of Soft Switching Techniques for Two-transistor Forward Converter (Two-transistor 포워드 컨버터에서 소프트 스위칭 기법의 손실 분석)

  • 김만고
    • The Transactions of the Korean Institute of Power Electronics
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    • v.6 no.5
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    • pp.453-459
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    • 2001
  • In this paper, the loss analyses of two soft switching techniques for two-transistor forward converter are performed. The sums of snubber conduction and capacitive turn-on losses for two transistors are calculated to compare the losses of the two techniques. While the conventional soft switching technique shows the loss difference between two transistors, the proposed soft switching technique shows equal as well as lower losses In two transistors. Thus, it can be said that even thermal distribution and higher reliability can be obtained by the proposed soft switching technique.

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Computations of Losses and Temperatures in the Core Ends of a High Voltage Turbo-generator

  • Liu Yujing;Hjarne Stig
    • KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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    • v.5B no.4
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    • pp.299-305
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    • 2005
  • The work described in this paper is to investigate the additional iron losses and consequent temperatures in core ends of a turbo-generator wound with high voltage cables. Electromagnetic calculations are made with 3D FE models, which include the lamination material with anisotropic properties both in magnetic permeability and electric conductivity. The models also include the geometry of the stator teeth and eventually the axial steps designated to reduce the core end losses. The 3D model of the rotor consists of field windings with straight in-slot parts and end windings. The thermal models are simplified into two dimensions and include the heat sources dumped from the 3D electromagnetic solutions. The influences of power factor on additional iron losses are studied for this cable wound machine and conventional machines. The calculation results show that the additional iron losses can be reduced to about $15\%$ by introducing some small steps around the airgap corner of core ends.

Convenient Thermal Modeling for Loss Distribution method of 3-Level Active NPC Inverter using Newton's Law of cooling (Active NPC 인버터의 손실 분배 제어를 위한 뉴턴의 냉각법칙 기반의 간단한 열 모델링 기법)

  • Hyun, Seung-Wook;Lee, Jung-Hyo;Won, Chung-Yuen
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.29 no.9
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    • pp.71-80
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    • 2015
  • This paper proposes a convenient thermal modeling method for loss distribution control method of 3-level Active NPC(Neutral Point Clamped) inverter. In the drawback of conventional 3-level NPC, the generated losses can occur unbalance in each switching device, as a result, thermal utilization of designed system has been decreased. In order to compensate unbalanced losses, Active NPC inverter performed loss balancing control with thermal modeling during operation of each switching device. Therefore, this paper deals with a convenient thermal modeling method based on newton's law of cooling rather than conventional thermal modeling method. Both simulation and experimental results based on 10kW 3-level Active NPC inverter confirm the validity of the analysis performed in the study.

Surface temperatures of public buildings, built in 1880, 1970 and 2002, in Northern Greece

  • Kosmopoulos, P.;Kantzioura, A.
    • Advances in Energy Research
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    • v.1 no.1
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    • pp.79-95
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    • 2013
  • The purpose of this paper is to investigate the surface temperatures of the shelter of three public buildings in the city of Xanthi, in northern Greece. The buildings were built in different time periods and consequently they have different technical characteristics. Respectively, we survey the three following buildings that have been built in 1880 (Municipality Hall of Xanthi), in 1970 (Municipality Amphitheatre) and in 2002 (Bank offices building). Data have been gathered by the use of thermal camera and the survey has been conducted from January up to July. The data gathered regard measurements of the surface temperature of the exterior walls of the shelters, both inside and outside. The study aims at the evaluation of the thermal behavior of the shelter of buildings, which built in different time and under different regulations. The gathered data of the surface temperatures compare the different thermal behavior of the shelter. The analysis of the results and diagrams show that the thick masonry of the traditional Municipality Hall offers an insulation that is adequate. The building of 1970, which was constructed with the previous buildings regulation, has thermal losses due to inadequate insulation. The new building of 2002 has low thermal losses.

Study on Thermal Stability Characteristics of Surge Arrester for High Power (전력용 피뢰기의 열안정화 특성)

  • Han, Se-Won;Cho, Han-Goo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07b
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    • pp.1142-1145
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    • 2004
  • ZnO surge arresters continuously endure the operating voltages during the operation course, and in the mean time, which need to withstand occasionally transient voltages of lightning and switching overvoltages. Under these voltages, the ZnO varistors inside arresters would have aging phenomena, one important result of aging phenomena is the increasing of resistive currents of varistors, which leads to the increasing of power losses of varistors. And the operating voltage is continuously applied on the ZnO varistors, there is a degradation phenomenon existing in ZnO varistors. When the degradation reaches a certain degree, then the arrester must stop operation. The degradation is related to the applied voltage ratio, the applied voltage ratio is high, the degradation is quickly. When the power loss is higher than the thermal dispersion ability of house of arrester, then the arrester will thermally breakdown. In this study the thermal stability characteristics of surge arresters for high power wil be discussed on the view point of watt losses and thermal breakdown.

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An Exploratory Study of Material Flow Cost Accounting: A Case of Coal-Fired Thermal Power Plants in Vietnam

  • NGUYEN, To Tam
    • The Journal of Asian Finance, Economics and Business
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    • v.9 no.5
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    • pp.475-486
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    • 2022
  • The purpose of this paper is to examine the use of material flow cost accounting (MFCA) in Vietnam's coal-fired thermal power plants. This study is based on the contingency and system theories to explain the application of management tools and analyze steps of input, output, and process in manufacturing. Costs in producing process-based MFCA include material cost, energy cost, system cost, and waste management cost. The exploratory case study methodology is used to describe and answer two questions, namely "How coal flow cost is recognized?" and "Why waste in material consumption can be harmful to the environment?". By analyzing the Quang Ninh and Pha Lai coal-fired thermal power plants that are the typical plants, this paper identifies the flow of primary material in these plants as a basis for determining losses for the business. The material flow of coal-fired thermal power plants provides the basis for the use of the MFCA. The manufacturing of electrical items in these plants is divided into four stages, each with its own set of losses. As a result, some phases in the application of MFCA are suggested, as well as some other elements required for MFCA application in coal-fired thermal power plants.

Heat Characteristics Analysis of Synchronous Reluctance Motor Using FEM Coupled Electromagnetic Field and Thermal Field

  • Lee, Jung-Ho;Jeon, Ah-Ram
    • Journal of Magnetics
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    • v.15 no.3
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    • pp.138-142
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    • 2010
  • This paper reports the development of an analysis method in a synchronous reluctance motor (SynRM) using the finite element method (FEM) coupled with the electromagnetic field of the Preisach model, which represents an additional thermal source due to hysteresis loss and a thermal field. This study focused on thermal analysis relative to hysteresis and copper losses in a SynRM.