METHOD AND SYSTEM FOR CONTROLLING THE OUTPUT OF AN ENGINE DRIVEN WELDER

A method and system of controlling the output current/voltage characteristic curve of an engine driven alternator welder with a maximum open circuit output voltage, including a rotary engine, a three phase alternator, rectifier bridge having a number of electronic switching means for directing current to the output at an operating point determined by the firing angle of the switching means, means for sensing output current, means for sensing output voltage, and a microprocessor output control device for controlling the firing angles of said switching means in response to the sensed current and sensed voltage. The method and system comprising: means for creating a desired fixed slope operating current/voltage characteristic curve; means for sensing the present operating current/voltage point of the welder; and, means for changing the firing angles of said switching means to shift the current operating point to a new operating point on the desired, fixed slope current/voltage curve of the welder. Preferably, the switching means is an SCR for each phase of the alternator.