Three-phase transformers are devices commonly used in electrical power systems that transform the voltages of three separate phases (commonly referred to as A, B, C). These transformers enable the transfer of energy from one phase to the other phases or from phase to neutral. Each phase carries voltages placed 120 degrees phase difference to each other. Three-phase transformers are often used in industrial plants, electricity transmission lines and power distribution systems. These transformers provide more efficient energy transfer and are more compact than single-phase transformers. They also increase energy efficiency by minimising power loss in three-phase electrical systems. These transformers can generally be produced as oil-filled or dry type. Dry type three-phase transformers require less maintenance and are environmentally friendly. Oil-filled transformers are widely used in high power applications and use oil for cooling and insulation.