APPARATUS FOR CONTROLLING CURRENT IN SPOT WELDER

摘要

PURPOSE: A control device for the current of a spot welder using a dynamic resistance value and a control method thereof are provided to control welding current for guaranteeing welding quality. CONSTITUTION: A spot welder controls current supplied to two electrodes(2-1,2-2) through a transformer by the igniting angle of two thyristors. The current control device of the spot welder using a dynamic resistance value, comprises an ampere meter(5) measuring welding current between electrodes per cycle; a voltmeter(6) measuring welding voltage between electrodes per cycle; a storage device(8) storing a model dynamic resistance in optimal welding condition; and a control device(7) calculating a dynamic resistance between welding voltage and welding current and controlling the igniting angle of two thyristors to compensate a difference between the calculated dynamic resistance and the model dynamic resistance.