Controlling weld current pulsed wave shape during resistance welding of can bodies - includes DC rectifier and switch unit to enable current generation from input voltage

摘要

Electronic control unit (4) for a resistance welding current supply includes a DC rectifier (1) and switch unit (2) which feeds the prim. coils of the transformer (3) to enable generation of current (Is) from input voltage (Vt). Unit (4) controls the voltage (Vt) for the transformer such that for each half period T/2 a number of stepwise alternating positive and negative double pulses or pairs with a max. value (Yv) and interval period of time (Tau) is produced. This gives a weld current (Is) with a max. value (Yi) and a saw tooth shaped wave form for each pair of stepped pulses of voltage. The current wave increases from zero to (Yi) in time (Tau) and falls away to zero over a time (Tau). USE/ADVANTAGE - Esp. for resistance welding can bodies with roller electrodes. Controls the current wave form, esp. the max. current value so that more uniform quality is produced with respect to dimensions and strength. No excessive overheating is caused during welding.