A Precision Sequential Solid State Control Unit-An Electronic Control for Resistance Welding by Digital Technique

Abstract

An electronic digital solid state control unit for a spot-welder has been developed to control the durations of its four operations, viz. ‘squeeze’, ‘weld’, ‘forge’ and ‘off’, precisely and in synchronism with the mains frequency. Periods of each of these operations can be set as desired, in steps of 1-cycle duration, anywhere from 1 to 100 cycles duration of the supply mains frequency. Furthermore, during the chosen weld period, a better control of the weld heat can be obtained by setting the firing angle of ignitrons. Provision has been made for automatic repetitive or non-repetitive welding.

This unit uses all components indigenously manufactured except for two SCRs.

This unit can be easily adapted for application in any other process which requires number of sequential operations involving precise control of duration of each operation.