Calculation of electrical parameters for transient overvoltage studies on electrical machines
ABSTRACT Finite element models are developed for the calculation of the coil resistance, inductance and capacitance in rotating machine windings. Resistance and inductance are calculated by analyzing the time harmonic fields in the machine, taking into account skin and proximity effects as well as the magnetic flux penetration into the iron core. The capacitance is calculated by the analysis of the electrostatic field in the coil regions. The electrical parameters are obtained considering the contributions due to the slot and overhang sections of a preformed coil. The accuracy of the calculated electrical parameters was verified by a comparison of calculated results and test data in two high voltage motors. The calculated parameters can be used for developing machine winding models for switching transient studies.
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ABSTRACT: To study and locate partial discharge(PD) and analyze the transient state of power transformer, there is a need for a high frequency model of transformer winding and calculation of its parameters. Due to the high frequency nature of partial discharge phenomenon, there is a need for an accurate model for this frequency range. To attain this goal, a Multi-Conductor Transmission Line (MTL) model is used in this paper for modeling this transformer winding. In order that the MTL model can properly simulate the transformer behavior within a frequency range it is required that its parameters be accurately calculated. In this paper, all the basic parameters of this model are calculated by the use of Finite Element Method (FEM) for a 20kV winding of a distribution transformer. The comparison of the results obtained from this model with the obtained shape of the waves by the application of PD pulse to the winding in laboratory environment shows the validity and accuracy of this model.Journal of Electrical Engineering and Technology 01/2014; 9(1). DOI:10.5370/JEET.2014.9.1.154 · 0.52 Impact Factor
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ABSTRACT: Parasitic capacitances of motor play a very important role in analysis of bearing current of motor caused by PWM supply. In previous papers, parasitic capacitances generally were acquired from two-dimension symmetry model of motor. The effect of stator winding-end on coupling capacitance was ignored. In this paper, mechanism of common-mode voltage was introduced and equivalent circuit of common-mode of motor was proposed. Relationship between parasitic capacitances and bearing voltage was figured out. 2D and 3D Finite-Element model of motor were established based on geometric dimension of motor respectively which includes with winding-end treatment and not. It's found that length of extended straight part of stator winding and height of squirrel-cage ring are two main factors which can affect Csr dramatically. Optimized analysis of Csr based on the two factors was also carried out and optimized group of parameters had been obtained to make Csr achive the minimum value.Electrical Machines and Systems (ICEMS), 2012 15th International Conference on; 01/2012
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ABSTRACT: In order to study the very fast transient overvoltage (VFTO) distribution in the taper winding of a tesla transformer under high-frequency steep-fronted voltage surge, we built a distributed line model based on multiconductor transmission line (MTL) theory. We used a new hybrid algorithm combining finite-element-method (FEM) and interpolation formulas to quickly evaluate the induction coefficient matrix K by utilizing some characteristics of the taper structure. The turn-to-ground and interturn voltage distributions can be obtained by solving the telegraphist's equations in the frequency domain. We measured the voltage distribution inside the taper winding to find some ways to weaken the voltage oscillations. Here, we compare the results with numerical values.IEEE Transactions on Magnetics 04/2006; DOI:10.1109/TMAG.2005.862759 · 1.21 Impact Factor