Study of Characteristics of Capacitors, Having Non-Traditional Conical Electrode Shapes, For Charge Distribution, And Surface Current Sharing Density

Abstract

Wanadongri, Nagpur (M.S.) India 441110 Abstract: The objective of this paper is to study and discuss on the different characteristics, like charge distribution over the surface area of the electrode of a capacitor, surface current sharing density per unit height of the electrode, having non-traditional conical electrode shape in comparison with the traditional typical parallel plate capacitors, particularly used with power frequency of 50 Hz. The study shows that the nontraditional conical shape of a capacitor creates the nonlinear, exponential or polynomial functionality. It develops logarithmic polarization-distribution in the dielectric medium. This offers usan exponential / polynomial reactive power distribution along the surface. Keywords: Conical Shaped Electrodes, Capacitor, Charge distribution, current sharing. (Cup= capacitance with unit differential height of a parallel plate electrodes,)( Cuc= capacitance with unit differential height of conical electrodes) I. Introduction This paper has a discussion on the study of characteristics of a capacitor having nontraditional conical electrode shape.The focus of study is on charge distribution over the surface area of the capacitor electrode, surface current sharing density per unit height along the capacitor electrode, in comparison with the typical traditional parallel plate electrode capacitor. The initiation of this study taken place, when the capacitor bank failure problem in the industry, brought forward, by the Managing Director of M/s. Chaitanya Electromagnets, the registered vendors of M/s Siemens Ltd. Aurangabad. The power capacitor banks in their industrial set up observed repeated and random periodic puncture in any one of the capacitor plates in the power capacitor bank consisting of power capacitors, as shown in fig.1. These three phase capacitor bank formed by three parallel capacitors per phase. Whenever there happens a spike / harmonic current of high amplitude, more than sustaining capacity of the electrode plate thickness, that capacitor got punctured. The time-varying nature of electric arc furnace (EAF) gives rise to voltage fluctuations, which produce the effect known as flicker (1). The problem of flicker has become quite acute (2). During the Melt-down period the furnace operation the variations in system is very erratic, and violent, based on the large inductive load variations affect the power and reactive kilovolt amperes variations, and in load currents (3). The location of puncturing of one of the parallel capacitors at different locations, and at different instants in M/s Chaitanya Electromagnets, is shown by plain rectangles in the fig.-1. The diagnostic testing and openings of the punctured capacitors did not shown break down of dielectric medium, but surprisingly every time, the melting of a portion of an electrode metal film found. However, progress from surface charging to the flashover has not been clarified sufficiently (4). This compelled to think for safe passage of the high peak current density. One should provide the proper relation between that current density with area of cross section for conduction to the current spike. The situation can be understood from the fig. -1.