A single-phase power supply is the most common forms of mains supply. It is only in industrial units and manufacturing plants that you will find a three-phase power supply. Most small and medium businesses run on single-phase power supply as well. It thus makes sense to have a good idea about machines that are available in both single-phase and three-phase versions. Welders are common examples of such machines.
It makes practical sense to buy a single-phase MIG welder if you do not have access to three-phase power or if it is too difficult or impractical to arrange. But aside from the case of obvious limitations dictating need, there are some other reasons to opt for a single-phase MIG welder even when you have access to a three-phase power supply.
Single-phase MIG welders can technically be used with a three-phase supply by using one live and one neutral wire of a 4 wire system. This is far from ideal as there is no control over load specifications. More practical methods involve cyclo-converters and various types of transformers depending on the various ratings of the three-phase supply.
There are a lot of misconceptions regarding amperage and efficiency of three-phase and single-phase welders. The rule of thumb is that while a three-phase power supply is more efficient across most parameters, a single-phase power supply is more suited to lower loads. However, it is a myth that three-phase welders are more efficient. Welder efficiency or duty cycle is not dependent solely on the type of power supply. The only guaranteed difference is the current output capacity of the welder. Three-phase welders produce considerably higher amperage. Conversely, single-phase MIG welders will be able to work with metals that need low amperage.
Single-phase MIG welders are thus mostly used where high amperage is not required. For instance, it allows the user to work on thin sheets where too much current can severely damage the metal. Single-phase MIG welding can be used with thin metal sections and can create strong welds. Single-phase welders are commonly used by DIY enthusiasts and hobbyists. But even for professionals, it is good to have access to a form of uncomplicated welding.
Single-phase MIG welders can create welds with sufficient strength that will hold the joints on your equipment. They are sufficient for small and medium metal structures. Single-phase MIG welders from reputed brands have similar duty cycles to their three-phase brethren.
Single-phase MIG welders are also useful for people with small workshops where they need to carry out minor welding jobs every day. They are especially helpful in businesses related to metal fabrication and automobile garages. Such regular but relatively low current output work can be completed with a single-phase MIG welder easily without the need for too much power in the process.