Multiphysics Analysis of Isolator Contact under Steady State and Short Circuit Condition

Abstract

It is essential to know the forces acting on contacts of Isolator to achieve optimal mechanical oper- ation at the stage of designing. A major contribution is provided by the magnetic force associated with current constriction close to the small regions where electrical contact is provided. This cur- rent constriction is dependent on the actual resistance between two contacts. The actual resistance between two contacts known as contact resistance is function of contact force, contact area and hardness of contact material. Due to current constriction, temperature increases at contact surface which leads to overheating, thermal stress and deformation of contact and may damage contact permanently. The steady state temperature rise, Dynamic forces and temperature rise behaviour under short- circuit condition are important for reliable electric contacts. Decoupled electromagnetic and thermal analysis cannot give proper results, as contact resistance changes with temperature. The electromagnetic force is significant during short circuit condition which is omitted in mechanical, electrical and thermal coupled field analysis. Mechanical behaviour of the contact is also very important which is not considered during electromagnetic-thermal coupled FEM analysis. Considering all these effects, a 3-D coupled field finite element (FE) model of isolator is essential to predict its performance in steady state as well as short circuit condition. Electromagnetic forces and temperature can be derived using electromagnetic-thermal coupled analysis. These temperature and forces are used in thermal-mechanical coupled field analysis as an input. This coupled field analysis can be used to find temperature rise and electromagnetic forces which may cause deformation of isolator.