Optimization for HV Potentiometer
Wei‐Jiang Chen · 1999
Abstraet - Finite Element analysis of a high-voltage potentiometer used in a Television set is presented. The net field is a result of coupling between the current fields andthm$ectric fields. Techniques for optimization using SWIFT non-* programming method are developed to solve for shape 01 the semi-conductive layer in the potentiometer to even out the field strength distributions and reduce the risk of discharge fault. I. INTRODUCTION A schematic of the high-voltage potentiometer widely used in Television sets is shown in Fig. 1. When a high voltage is applied between terminals A and B, an electric potential distribution is generated along the semi-conductor layer. The electrical potential between terminals C and D will be different when the conductive arms are at different positions. The potential distribution on the layer in turn produces another electric field in air. So the potentiometer is a result of coupling between the electric current field on semi-conductor layer and the electric field in air. This paper presents a finite element (FE) model for analyzing this coupled phenomenon. A full three dimensional model of the geometry involves inhomogeneous regions comprising the thin semi-conducting layer and air surrounding it. In order to simplify the complexity of meshing the overall geometry, a two step modeling procedure is proposed. The first step solves for the current in the thin semi-conductor using a 2D FE model. The second step models a 3D homogeneous medium (air) and solves for electric field in air. The approach presented is not an approximation but the exact solution to the coupled problem. Discharge faults are a common problem in high voltage potentiometers. The purpose of the field analysis is to reduce the risk of discharge faults. It can be seen from the field analysis that the shape of the conductive layer, especially in the section between point E and F, plays an important role in minimizing the risk. Further more, the shape optimization is performed in order to modify and balance the electric field distribution in this section. Field optimization is an area of extensive research