An automatic welder is used in an internal welder unit (30) which travels along the interior of a pipeline and provides the interior weld passes at the junction of abutting pipe joints (32, 33). The internal welder unit (30) has an electronic control system which includes a plurality of microprocessor control units (92, 94, 96, 98), each of which performs specific functional operations for the internal welder unit (30). The control system directs the operation of orbiting internal welders (140) to have a zero or slow travel speed at a start point to ensure a high reliability of arc initiation. After the arc is started, the travel speed of the internal welders (140) is accelerated to a high speed rate for the majority of the weld pass. At then end of the weld pass, the welders (140) travel rate and wire feed rate are suddenly reduced to zero for the weld termination.