Effect of Ambient Temperature and Contact Force on Contact Resistance and Overtemperature Behaviour for Power Engineering Contacts

With switching devices for power engineering applications the question of overtemperature at steady state current becomes more important as the size of said devices decreases and/or rated currents increase. In order to evaluate the influence of parameters as contact material, contact force, ambient temperature, current and current flow time a PC driven model switch is build up with the ability to set these parameters easily. This paper describes the setup of the model switch and gives first results of tests related to typical conditions of MCCB with a rated current of 160 A. Parameter variations include contact force (5N to 30 N), ambient temperature (25°C to 125°C) and contact material (Ag/C, Ag/Ni, Ag/W, AgNi0,15). Results obtained are discussed on the background of contact surface roughness as well as contact material properties as electrical conductivity and hardness as a function of temperature.