Three - phase power supply can be achieved either by a single three - phase transformer or by interconnecting three single - phase transformers. A single three - phase transformer is more compact in size compared to an equivalent - capacity bank composed of three single - phase transformers.
Three - phase transformers are often used in underground switchrooms (or similar spaces) or as pad - mount transformers (see Figure 1). Figure 2 shows an example of a three - phase transformer.
Three - phase transformers are easier to install since the polarity and interconnections among phases are fixed. In overhead distribution systems, it is common to use three single - phase transformers.