Welder for continuous resistance flash-butt welding

Abstract

The primary winding of a welding transformer is provided with controlled rectifiers and the primary winding of a current transformer. The secondary winding of the current transformer is connected to a welding current pick-up. The phase angle of opening of the controlled rectifiers is varied through a phase shifter and a programmer. A pulse shaper is provided for shaping pulses synchronized with the voltage of a supply circuit and has an output connected to a phase delay unit. An OR circuit is provided having inputs connected to the output of the welding current pick-up and to one output of the programmer, and an output connected together with the output of the phase delay unit through AND logical circuits and an inverter to the inputs of a voltage switching flip-flop having outputs each being connected in pair with another output of the programmer through additional AND circuits to corresponding inputs of the phase shifter. The programmer incorportes a welding current pulsation frequency pick-up having an input connected to the secondary winding of the current transformer, a program halt unit, a welding time counter, a decoder, a 'weld-on' flip-flop, an output flip-flop unit, and logical circuits to provide interaction between the control signals within the programmer.