Inrush current is a very important phenomenon which occurs in transformer during energization at no load. It depends on several factors like magnetizing properties of magnetic material, resistant and inductance of primary winding, supply frequency, switching angle of circuit breaker, applied voltage etc. Objective of this study is to estimate the maximum value of transformer inrush current. Mea...

This study adopted previous fault patterns, results of detection analysis, historical records and data, and experts’ experiences to establish fuzzy principles and estimate the failure probability index of components of a power transformer. Considering that actual parameters and limiting conditions of parameters may differ, this study used the standard data of IEC, IEEE, and CIGRE as condition p...

The number and diameter of strands to minimize loss in a litz-wire transformer winding is determined. With fine stranding, the ac resistance factor can be decreased, but dc resistance increases as a result of the space occupied by insulation. A power law to model insulation thickness is combined with standard analysis of proximity-effect losses to find the optimal stranding. Suboptimal choices ...

Based on the analysis of operation principles of conventional self-exciting electronic ballast, the cause of high switching loss has been researched. In order to reduce switch temperature and increase the reliability of the whole circuit, drive circuit of self-exciting electronic ballast has been improved to achieve soft switch. Circuit simulations and experimental results are coincided with th...

Power transformers with superconducting windings need a protection system to prevent damage to the low-loss superconducting winding by an abnormally high current. The generally accepted protection technique which uses auxiliary coils has been analysed using a network representation. The current distribution between main and auxiliary coil is expressed in terms of geometrical parameters. Experim...

Abstract: A method for calibrating multi-decade inductive voltage dividers has been developed which makes it possible to determine both the inphase and the quadrature error for ratios of i /11, i = 1, 2, ..., 10 in the frequency range from 400 Hz to 5 kHz. Calibration is made by comparing the divider under test against a reference two-stage divider having a ratio winding with 11 identical secti...

This paper presents the results of investigations on a planar sandwich air-gapped transformer with two different winding configurations. Experimental results of the coil self inductances, voltage ratio versus frequency, and the numerical results for the magnetic flux and eddy-current distributions are presented. It is shown that the voltage ratio and turns ratio are not equivalent and that the ...

In order to ensure the safe and stable operation of a power system, performance evaluation transformer windings after short-circuit test can predict whether are deformed in provide useful reference for maintenance sector. This paper proposes method evaluating improve overall effectiveness winding evaluation. The index data obtained based on impedance method, frequency response oscillation wave ...