Welding Processes Power Supply, part 3
The welding equipment and machines are rated in accordance to the duty cycle they have, as commercial welders know. The duty cycle is often misunderstood and thus it this term has to be cleared. The duty cycle is based on a period of ten minutes. When we have rated voltage, a power supply with a 100% duty cycle rating is in the position to operate without stopping at or below its rated current.
When we have a 50% duty cycle, this does not mean that the commercial welder will have a cycle to operate 50% of the time at rated voltage and current. In such cases it means that the welder can operate only 5 minutes on every 10 minutes at that voltage and that current. This means that the welding equipment in such cases should be left idle five of every 10 minutes. The welding machines that are rated for a duty cycle of less than 100 % can be used without stopping by decreasing the current rating.
Tig welders who are performing Tungsten Arc Welding are using inert shielding gases. This is not a new process, but it is an important one as it could be applied to various difficult welding problems. Among these difficult welding situations is included the welding of exotic and difficult to weld materials including aluminum and magnesium, copper and beryllium copper, stainless steels and Hastelloy, etc.
The TIG welding processes are done with the same power source type as the shielded metal arc, or the stick electrode welding through a drooping volt-ampere output curve. The conventional AC power supply that is not specifically designed for TIG welding should be set for AC TIG service. The problems associated with the TIG welding include overheating of the main transformer, arc stabilization and arc starting, plus control of all welding variables.
In many welding applications today, the gas metal arc welding uses consumable wire electrode fed all the time to a gas shielded arc zone. It has replaced the conventional shielded metal arc (stick electrode) welding and the non-consumable tungsten inert gas welding. The speed here is the main reason, as it is several times faster than other processes. The other advantages here include the cleaner welds with no oxidation, the electrode savings through no stub losses, as well as the excellent weld physical and metallurgical characteristics.