A HIGH POWER GENERATOR OF GAS METAL ARC WELDING – SPRAY TRANSFER MODE

Abstract

A high-power generator was designed for gas metal arc welding – spray transfer mode. The switching frequency of the H-bridge inverter was fixed at 30 kHz. The inverter unit consisted of four transistor modules (insulated gate bipolar transistor, IGBT) of the MG12200D-BA1MM N-channel type. The high level of the gate-emitter control pulses was 15 V, and the low level of the gate-emitter control pulses was 0 V. The generator had three basic operating points: the first point was at an output current of 150 A with a pulse width of 10 μs (duty cycle 30 %), the second point was at an output current of 200 A with a pulse width of 13 μs (duty cycle 40 %), and the third operating point was at an output current of 250 A with a pulse width of 17 μs (duty cycle 50 %). The wires (0.035 inch ER70S7, 0.035 inch ER70S7, 0.035 inch ER70S7) were used as the electrodes for the output currents of 150, 200, 250 A respectively. A coil (Ls) of 10 μH and a variable resistor (Rs) of 10 Ω were connected in series to limit the output current of the generator.