Several designs now exist for the electrode arm and bus-bar assembly. Many older furnaces utilize an arm structure that supports an electrically insulated bus-bar. The bus-bar provides the electrical connection between the power cables and the electrode holder. Bus-bars consist of a rigid, round, copper pipe. Typically the bus tube is supported by one or two bolted connections. Good insulation must be installed between the bus tube and its' supporting members to ensure that arcing which could destroy the bust tube does not take place. Bus tubes are usually attached to the power cables using removable, cast copper terminals or in some cases, permanent fabricated copper terminal plates and pads.
Several configurations are available for the bus tube termination at the electrode holder and contact pad. These include flanged connection to the contact pad, flat blade joined to the tube for parallel connection with the holder and a round copper tube contact point with the connector. The bus tubes may be bolted to the holder or contact pad or a fused permanent joint may be used.
Many modern furnaces utilize current conducting arms in which the arm itself transmits electricity to the electrode holder and contact pad. Current conducting arms are usually fabricated from copper clad steel or aluminum alloys. Due to the reduced weight of conducting arms as opposed to conventional arm and bus tube assemblies there is somewhat less mechanical wear. However, many of the same maintenance issues apply both to bus tube assemblies and current conducting arms.