Replacement of AgCdO by AgSnO2 in DC contactors

According to the amendment 5 of the European Parliament new electrical and electronic equipment must be free of cadmium until 1^st of July 2006. In new AC and DC contactors for low voltage application in automation this replacement was completed during the last years. In order to fulfill the demands of the European Parliament also in DC contactors for application in transport, e.g., trains, it is necessary to replace AgCdO by a contact material with comparable contact properties. This work reports the comparison of AgCdO12 with four different AgSnO₂ materials tested in two different contactors at voltages between 72 and 220 VDC. The inrush currents were 800 A and 1900 A, the continuous thermal currents being 100 A and 300 A, respectively. Both contactors were originally optimized for AgCdO. The comparison of test results shows, that the commercial available AgSnO₂ materials have the potential to replace AgCdO without changing the design of the contactors. Best results concerning temperature rise and switching capacity are obtained by a die compacted AgSnO₂12 contact material produced from precipitated AgSnO₂ powder.