A transformer is designed to create a magnetic field which occurs naturally when a fluctuating electrical current is passed through a wire. This magnetic field will have a strength which is directly in balance with the strength of the electrical current. This magnetic field generates an electric current within the wire at the same time.
With a second electrical wire, a winding, in close proximity to the electrical wire with the electric current, the second wire will also have a similar electric current. In this way, the primary wire with the direct current is able to pass the electrical current to the secondary winding without any contact.
This is done through induction through electromagnetics. By adding a core of ferrous or other material, this transmission of the electrical energy is even more efficient. It can be used to step up or step down the original voltage.
The 3 Phase Difference
The description above is a basic single phase transformer. With a 3 phase transformer, the same principles apply, but there is the advantage of three single phase transformers using a single core. In other words, it would be possible to create the same effect by wiring together three single phase transformers. While this does offer some additional protection should one transformer fail, the offset size, cost of production and drop in efficiency of the system is important to consider.
Lower Cost of Development
With only a single core and not three cores, each with two winding and each connected to each other, the 3 phase transformer offers a lower cost of production. It is also much easier to install as it is one unit, not three units. Smaller, lower in weight and easier to mount and position in equipment, this is the ideal solution in virtually all types of systems and components.
It is also worth noting that the 3 phase transformer can operate as a single phase supply when needed. With three phase equipment, a single phase transformer cannot be used, which limits versatility
