The present invention goes generally to welding systems and, more particularly, to a method and apparatus of electronic selection of an output mode of a welding power source. Specifically, the present invention includes operational circuitry that electronically and selectively energizes an output terminal of the power source based on an output mode selection by a user.
Power sources are commonly used in welding-type processes such as welding, plasma cutting, and induction heating to condition a raw power input from a utility or generator into a form usable by the welding-type process.
Some welding-type processes can be categorized into various modes and power sources have been designed so as to be operable with the various modes. For example, MIG welding, formerly known as Gas Metal Arc Welding (GMAW), is one welding process that combines the techniques and advantages of TIG welding's inert gas shielding with a continuous, consumable wire electrode. Two examples of MIG welding modes are constant voltage (CV) or constant current (CC). Should a user select CV mode, a user selected voltage is generally required. The voltage is an indication of the voltage desired at a point of a weld and is held constant by the power source. It is also necessary to select an initial wire feed speed (WFS). The WFS indicates the speed with which metal filler is delivered to the point of the weld but when the mode is CV, also corresponds to an output current. By holding the output voltage constant, the user can manipulate the output current by adjusting the WFS. Since the WFS is directly proportional to the current delivered to the wire feeder and point of the weld, the higher the WFS, the greater the current delivered to the weld. However, should the user choose CC, the user input current is held constant and the user can adjust the WFS to obtain the desired voltage at the weld. In this case, the user must lower the WFS in order to raise the voltage at the weld or raise the WFS to lower the voltage at the weld.
The above-described arc control process is well known and is a standard technique of controlling the power source to provide a user selected output at the weld. However, it is simply not sufficient with known power sources for the user to identify an output mode. That is, most MIG welding power sources include a CC terminal as well as a CV terminal. Accordingly, if the user intends to carry out a CC welding process, then the weld cable extending from the wire feeder must be connected to the CC terminal of the power source. Conversely, if a CV welding process is to be carried out, then the weld cable extending from the wire feeder must be connected to the CV terminal. Conventional power sources have a mechanical switch that must be manually operated to energize the appropriate output terminal. In this regard, the user must manually select the output inductance and selectively energize a number of capacitive elements such that the appropriate output terminal is energized. The mechanical switch assembly typically found in power sources to selectively energize an output terminal to be consistent with the output mode selected by the user in prescribing a particular welding process is a relatively complex assembly that not only increases the complexity of the power source, but also adds additional cost to the manufacturing process. Additionally, implementing a mechanical switch to energize the appropriate terminal of the power source requires that the user take additional steps to insure proper commencement of the welding process.
Mechanical output mode selector switches is not limited to selection between a CC output terminal and a CV output terminal of a MIG welding power source. That is, power sources have been developed that may be usable to provide power for welding as well as plasma cutting or induction heating. With these power sources, a user must mechanically energize output terminals based on the particular welding-type process to be carried out or load placed on the power source. For example, to switch between welding and plasma cutting, the user must mechanically operate a switch designed to selectively energize an output terminal for plasma cutting rather than an output terminal for welding.
It would therefore be desirable to design a method and apparatus of electronically energizing isolated output terminals based on a user selected welding parameter.