Electric Field Between Contacts of Fast Mechanical Switches Subjected to Fretting Wear

Fast Mechanical Switches (FMS) are a key component of energy-efficient hybrid circuit breakers for DC applications. Wear of the FMS impacts the performance and life expectancy of the breaker. The surface damage caused by fretting motion can alter the contact surfaces and reduce the voltage withstand capability of the FMS, especially in those that operate at sub-millimeter contact separation. This paper investigates the issue by conducting fretting experiments on copper contacts as a function of current magnitude to obtain surface parameters of the damaged contacts. Random surfaces based on the measured surface parameters are generated in a finite element software package. The electric field between the generated surfaces is obtained using electrostatic field modeling to calculate the probability of electric breakdown in the contact gap. The results are used to understand the potential impact of fretting on the breakdown voltage of FMS.