MAG arc welding apparatus

A pulse MAG arc welding apparatus for carrying out an arc welding operation by supplying a pulse welding current that switches between a first pulse current group for generating a short arc length and a second pulse current group for generating a long arc length, said apparatus comprising:

• an arc voltage detecting circuit for detecting an arc voltage value and outputting an arc voltage detecting signal corresponding thereto;
• a first arc voltage setting circuit for setting a value of arc voltage in accordance with welding conditions and outputting a first arc voltage setting signal corresponding thereto;
• a second arc voltage setting circuit for setting a value of arc voltage in accordance with welding conditions and outputting a second arc voltage setting signal corresponding thereto;
• a comparison circuit for comparing said arc voltage detecting signal with and arc voltage setting signal and outputting a difference between said two signals as an arc voltage control signal;
• a pulse condition control signal generation circuit for generating a pulse condition control signal for controlling one preselected pulse control condition from among four pulse control conditions in common with said first and second pulse current groups in accordance with said arc voltage control signal, said four pulse control conditions comprising pulse frequency, pulse width, base current value and peak current value;
• a pulse current setting circuit for setting the remaining three pulse control conditions for said first pulse current group and said second pulse current group which have not been preselected and for outputting pulse current group setting signals including setting signals corresponding to remaining three pulse control conditions other than said pulse condition control signal;
• a switching circuit for generating a switching signal for switching said first and second pulse current setting circuits alternatively at a frequency ranging from 0.5 to 25 Hz;
• a pulse frequency signal generation circuit for generating a pulse frequency signal in response to either the pulse frequency control reference signal if output from said pulse condition control signal generation circuit, or, the pulse frequency setting signal output from said pulse current setting circuit if not output from said pulse condition control signal generation circuit;
• a pulse frequency and width signal generation circuit for outputting a pulse frequency and width signal in response to
• the pulse frequency control signal and pulse width setting signal if the pulse frequency control reference signal is output from said pulse condition control signal generation circuit,
• the pulse frequency signal and pulse width control signal if the pulse width control signal is output from said pulse condition control signal generation circuit, or
• the pulse frequency signal and pulse width setting signal if the peak current control signal or base current control signal is output from said pulse condition control signal generation circuit;
• a pulse current control circuit for outputting a first pulse control signal and a second pulse control signal alteratively in response to
• the pulse frequency and width signal, the peak current setting signal and base current setting signal if the pulse frequency control reference signal or the pulse width control signal is output from said pulse condition control signal generation circuit,
• the pulse frequency and width signal, the peak current control signal and base current setting signal if the peak current control signal is output from said pulse condition control signal generation circuit, or
• the pulse frequency and width signal, the peak current setting signal and base current control signal if the base current control signal is output from said pulse condition control signal generation circuit;
• and
• a welding power source control circuit for outputting the first pulse current group when the first pulse control signal is output from said pulse current control circuit and the second pulse current group when the second pulse control signal is output from said pulse current control circuit.