According to equivalent circuit of the main welding circuit, a mathematic model was
derived for maximum output power of theК-type alternative current rail flash butt welding
machines. Based on the model, a high efficiency welding procedure was proposed, and the control
program was designed. Experiments were conducted on aК900 rail flash welding machine by setting
different welding currents at high voltage stages to determine the time at this stage. The
experimental results indicate that welding time at high voltage stages is short when welding current
at high voltage stage is close to the welding current corresponding to highest output power of the
machine. Therefore, with the proposed procedure, the rail under welding can be heated fast,
shortening the welding time and increase the productivity.