Calibrations of Resistance Welding Equipment With High Pulsed Currents

Rogowski coils are widely used as high pulsed current sensors in resistance welding applications. The operating conditions of the coils determine the requirements for their calibration. A new calibration system has been developed at National Research Council (NRC) Canada for calibrating current sensing coils and weld current monitors (WCMs) used in AC resistance welding. The calibration system, which includes a high-current source and a coaxial copper cage, has been evaluated at peak pulsed currents of up to 80 kA at 60 Hz. The expanded measurement uncertainties (k = 2) have been estimated to be less than 350 μA/A for magnitude. A method for the calibration of WCMs separately from their Rogowski coils at conditions that correspond to those obtained at high pulsed currents but without the need to use actual high pulsed currents has also been developed.