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Online ISSN 1751-8679 Print ISSN 1751-8660

IET Electric Power Applications

Volume 6, Issue 5, May 2012

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Volume 6, Issue 5

May 2012

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    • Winding factor calculation for analysis of back EMF waveform in air-core permanent magnet linear synchronous motors
      • Author(s): A. Mohammadpour ; A. Gandhi ; L. Parsa
      • Source: IET Electric Power Applications, Volume 6, Issue 5, p. 253 –259
      • DOI:  10.1049/iet-epa.2011.0292
      • Type: Article
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      • p. 253 –259 (7)
        This study presents an analytical method for winding factor calculation and back electromotive force (EMF) prediction in air-core permanent magnet linear synchronous motors. In the proposed method, the voltage on each coil of a phase winding is calculated by adding the voltage induced in individual conductors considering a phase shift proportional to the conductor diameter. The proposed method can be used to find back EMF waveform of air-core linear motors with any winding configuration in terms of dimensional specifications of magnet track and winding assembly. Once the back EMF equation is obtained, it can be used to predict the thrust of the motor.The results of the proposed analytical model are compared with finite element analysis results for three different motors to verify the validity of the proposed modelling method. In order to investigate the effect of simplifying assumptions in model derivation, experimental back EMF result on a three-phase eight-pole motor is presented and compared with the proposed analytical model.
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      Thermal–fluid transient two-dimensional characteristic-based-split finite-element model of a distribution transformer
      • Author(s): M.A. Arjona ; R.B.B. Ovando-Martínez ; C. Hernandez
      • Source: IET Electric Power Applications, Volume 6, Issue 5, p. 260 –267
      • DOI:  10.1049/iet-epa.2011.0286
      • Type: Article
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      • p. 260 –267 (8)
        This study presents a two-dimensional (2D) finite-element (FE) linear model for predicting the thermal and fluid dynamics of an oil-filled distribution transformer. The model is based on the solution of the Navier–Stokes and Maxwell equations which are weakly coupled. Two electromagnetic FE models are used to calculate the load and no load losses of the transformer. The thermal–fluid equations are solved using first-order 2D FE and the characteristic-based-split (CBS) scheme. The CBS is used for the first time in the thermal fluid modelling of a transformer thereby is the proposed contribution of this study. The CBS algorithm is applicable to all ranges of flow and gives the same results as specialised methods such as the Petrov–Galerkin and Taylor–Galerkin methods. A natural convection analysis for an incompressible Newtonian flow in a distribution transformer is presented. Convection, radiation and symmetry boundary conditions are taken into account in the model. The model predictions are compared against those obtained with a commercial software and good agreement was obtained. The proposed model was programmed in C language.
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      Transformer winding faults classification based on transfer function analysis by support vector machine
      • Author(s): M. Bigdeli ; M. Vakilian ; E. Rahimpour
      • Source: IET Electric Power Applications, Volume 6, Issue 5, p. 268 –276
      • DOI:  10.1049/iet-epa.2011.0232
      • Type: Article
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      • p. 268 –276 (9)
        This study presents an intelligent fault classification method for identification of transformer winding fault through transfer function (TF) analysis. For this analysis support vector machine (SVM) is used. The required data for training and testing of SVM are obtained by measurement on two groups of transformers (one is a classic 20 kV transformer and the other is a model transformer) under intact condition and under different fault conditions (axial displacement, radial deformation, disc space variation and short circuit of winding). Two different features extracted from the measured TFs are then used as the inputs to SVM classifier for fault classification. The accuracy of proposed method is compared with the accuracy of past well-known works. This comparison indicates that the proposed method can be used as a reliable method for transformer winding fault recognition.
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      Life cycle assessment of a three-phase electrical machine in continuous operation
      • Author(s): W. Boughanmi ; J.P. Manata ; D. Roger ; T. Jacq ; F. Streiff
      • Source: IET Electric Power Applications, Volume 6, Issue 5, p. 277 –285
      • DOI:  10.1049/iet-epa.2011.0219
      • Type: Article
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      • p. 277 –285 (9)
        This study presents an analysis of the global environmental impacts of a three-phase machine operating in continuous service. The industrial production of electric motors requires raw materials, the suitable industrial tools for mass production and a transportation system able to bring each motor to its right place. During the use phase, the motor losses correspond to extra energy consumption and the corresponding environmental impacts for a given local electricity production system. End-of-life scenario corresponds also to extra pollution. During each phase, greenhouse gas and other pollutants specific to the manufacture of electrical machine are emitted. Therefore the improvement of the global quality of electrical machines needs a comprehensive analysis of the environmental impact. This study applies the life cycle assessment (LCA) procedure to the AC machines. The authors evaluate the environmental impacts for a standard 10 kW machine for all the phases of its life cycle (construction, use, end-of-life), and also propose several improvements, which are analysed.
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      Calorimetric system for measurement of synchronous machine losses
      • Author(s): P. Rasilo ; J. Ekström ; A. Haavisto ; A. Belahcen ; A. Arkkio
      • Source: IET Electric Power Applications, Volume 6, Issue 5, p. 286 –294
      • DOI:  10.1049/iet-epa.2011.0241
      • Type: Article
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      • p. 286 –294 (9)
        An open-cycle air-cooled calorimetric system for the measurement of power losses of a 150-kVA synchronous generator is described. The enthalpy increase and mass flow of the cooling air are determined by measuring the temperature rise, relative humidity, absolute pressure and the pressure drop over a known aerodynamic resistance. The loss measurements are performed using the balance method by calibrating the system against a set of heating resistors. In addition, the difference in heat leakage between the balance test and actual test run is determined by measuring two additional calibration curves. The losses of the test machine are measured in three different loading points. From the error analysis, measurement errors of 5.0 and 1.9% are obtained for the total electromagnetic loss at no load and in rated-load operation, respectively.
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