A comparative study of arc erosion at frequencies ranging 50–1000 Hz

Studies have been conducted of AgCu contacts to investigate the influence of current frequency on the rate of the arc erosion at contact opening. The work is performed on a special designed test rig at the current of 100 A, frequencies ranging from 50 Hz to 1000 Hz, operating voltage of 110 V, contact gap of 3 mm for 1000 operations. It was found that that the rate of erosion depends nonmonotonically on the current frequency and decreases at a frequency greater than 500Hz. The mathematical model is presented to explain this phenomena. It is based on the system of differential equations describing dynamics of arc temperature, energy and material transfer from one contact to another. The results of calculation show that the arc temperature maximum shifts to a greater time values when the current frequency increases. Shifting of the arc temperature maximum in time entails the change of the time duration Δt when the arc temperature is greater than the temperature of gas ionisation (~ 5000 K) at which evaporation is more intensive. These phenomena can explain nonmonotonical dependence arc erosion on the current frequency. The main result is that erosion decreases at the current frequency greater than 500 Hz.