Connections and working principles of three - phase distribution transformers

Three - Phase Transformers

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.

Connections and Working Principles of Three - Phase Distribution 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.

When single - phase transformers are used in combination, they can be interconnected to provide various types of power supply services. For instance, three transformers with a secondary voltage of 120/24V can supply 120/208V, 240/416V, or 240V three - wire power services.

When employing single - phase transformers, fewer specialized emergency standby transformers are required.