Progressive current limit control for a resistance welder

摘要

A weld controller employs a stepper program for increasing heat boost in one percent increments or steps to provide compensation for contact tip wear. The weld controller acquires weld current data in the form of current samples for each step to create a characteristic curve or nominal current profile for the stepper program. Subsequent operations of the weld control utilize high and low current limit thresholds that track the nominal current profile. The thresholds can be defined as a fixed offset from the profile or as a percentage of the profile at each step of the stepper program. This allows the use of current limits to be established in close proximity to the nominal weld current at all times, enabling the use of tighter tolerances.