Welding in Break and Make Operations for CuMo and CuW Contact Materials in DC200–500V and Different Surrounding Gases

Hermetically sealed electromagnetic relays or contactors with high DC switching capacity, smaller size and longer lifespan are getting more and more important nowadays due to rapid developments of renewable energy installations and electrical vehicles. However, reports on contact welding resistances, arc durations and other related characteristics in DC200-1000VDC load ranges are quite few. In this paper, experiments were conducted with CuW70 and CuMo85 contacts in the following conditions: DC power voltage 200 to 500V, load current 40 to 150A, surrounding gases of air, N
₂
, CO
₂
, Ar, O
₂
, and mixtures of CO
₂
and Ar. Contact welding in both breaking and making operations was detected and analyzed. Percentages of welding in making operations were in general higher than those in breaking operations. Welding percentages of CuW in breaking operations were much lower than those of CuMo. Contact welding tendency in air is the least, but in the mixture of CO
₂
/80% and Ar/20% is the most. Higher current levels generally caused more welding occurrences than higher voltage levels.