What Is a Three-Phase Transformer and Where Are Three-Phase Transformers Used?

An electric power grid distributes power from the electrical utility to residential buildings, schools, and commercial and industrial properties along the way. While single-family homes typically require only single-phase power, buildings with electrical needs involving high-power equipment like industrial machinery, heavy-duty power protection equipment and uninterruptible power supplies, semiconductor and ion beam systems, or large-scale information systems consistently use three-phase power.

As the name suggests, three-phase transformers are designed to transform the line or input voltage supplied by a three-phase source to the voltage required by a three-phase load on the output side. Where step down transformers deliver a lower secondary or output voltage than the primary or input voltage, step up transformers do the opposite. In other cases, where the available line voltage matches that of a machine or system, a transformer is often needed to isolate and therefore protect the equipment under load or other downstream components in the circuit from various disturbances and electrical noise on the line side that might otherwise compromise performance or shorten their useful life. A three-phase transformer can also be designed to deliver a given output voltage across a range of input voltages to accommodate variations in line voltage, step-up or step-down, from one location to another. A custom-designed three-phase transformer can be configured to supply a combination of relatively balanced single-phase loads or a low-power single-phase component in addition to its main three-phase load as well.