Appropriate Polymer Selection for Insulation of High Voltage Ignition Coils by Combination of Material Index Determination and Novel Heuristical Approach

Abstract

Ignition coils are a device which basically acts as steps-up transformers to provide proper sparks. Ignition coils have been subjected to harsh conditions and can fail due to unnecessary discharges. The insulation material needs to fulfill the specific properties required for insulation. It should provide resistance against unnecessary discharges by having higher breakdown voltage. In addition, insulation material must be able to transfer heat to environment and protect coil from dust particles, greases and lubricating oils. To minimize the probable failures, proper insulation material shall be selected which can withstand high voltages such that to get high quality coils. Initially, three material indices were derived, i.e., Emax × er, Emax × k and Emax/T to screen adequate materials for this application which were not known in any previous literature study. The main objective is to maximize the breakdown voltage. Hence, Emax × er, Emax × k and Emax/T were plotted on Cambridge Education System software to screen the appropriate materials for this application. 14 out of 677 materials were shortlisted using aforementioned procedure. Afterward, further selection was made using a new heuristical formula which has been named as critical, objective and subjective factor (COSF) approach. Finally, the selected material, i.e., polyester with chopped glass fiber was used to manufacture the coils which were tested using IS-14380. Experimental results validated theoretical material selection. Bubbles and cracks are the prominent defects that significantly affect the insulation quality. Cracks are generally formed in epoxy-based insulators. In this research, a systematic procedure has been adopted to select high voltage insulating materials for the ignition coil polymeric insulation using CES software and novel heuristic approach which are having better properties in comparison with existing materials.