The Power supply of the Welding Processes
Commercial welders use conventional stick electrode, also called ’constant current machine’ and a ’dropper’. This is so as the voltage used in this weld drops as the welding current goes up, resulting in its volt- ampere output curve ’droops’.
When the welding equipment used is turned on with no arc and no current flowing, the machine has a high open circuit of up to 80 volts. The welding is done at the steeper curve and this position is ideal for performing manual stick electrode welding. The arc voltage here depends on the physical length of the arc which is set between the weld and the electrode.
Multiprocess welders know that this cannot be held constant when they perform manual welding. The burn off rate of the filler wire is determined by the current and this burn off stays constant in case the current does not vary.
This type of welding equipment and welding machine has many variations which are based on the single or three phase power input and on the AC, DC or AC / DC power output, as well as on the mechanical or electrical output control type.
Arc welders use also another type of arc welding power supply which produces a constant voltage. The voltage here may vary from zero to very high short circuit current. These welding equipment and machines are designed for gas shielded metal arc welding and is not in fact suitable for stick electrode welding. As every good stick welder knows, there are no welding machines that can produce can constant voltage.
The truth is that the voltage drops with at least one volt on each 100 amp output. However, the short circuit currents can reach several thousand amperes.
As a rule, the constant voltage machines work with lower open circuit voltages compared to the constant current machines. In such cases in order to obtain the desired arc voltage, the commercial welder can set open circuit voltage on the welding machine.
As multiprocess welders are aware, the welding current is in the position to reach several thousand amperes at short circuit. The current adjusts itself to burn the filler rod metal at sufficient rate to maintain the arc length that is required by the present voltage and the rate of electrode feed.