Inverter seam resistance welding electric power supply apparatus

摘要

An inverter seam resistance welding electric power supply apparatus reliably determines the local weld quality as conforming or defective of seam welding by simply monitoring welding current. This improves the quality of seam welding. In a seam welding operation, when a current monitor time interval has elapsed, CPU 38 reads stored measured current values [I1], [I2], etc., of each inverter cycle obtained during the current monitor time interval and computes an average current value [IM1] thereof, according to an averaging method such as arithmetic mean method (step S9). Then CPU 38 compares the average current value [IM1] with preselected monitoring value or range. If the average current value [IM1] falls within the monitoring range, CPU determines conforming local welding whereas it determines defective local welding if the average current value goes out of the monitoring range (step S10). If defective local welding is indicated successively more than say three times (step S11), CPU 38 determines defective seam welding (step S12), and takes appropriate action immediately, for instance, stopping the seam welding operation (step S13).