This course introduces the theory of three-phase circuits, as well as single-phase and three-phase transformers and their applications in residential, commercial, and industrial wiring. The advantages of a three-phase system are discussed, as well as the concepts of operation of isolation, autotransformer and instrument transformers. Emphasis is placed on The Canadian Electrical Code as it is used for the sizing of conductors and overcurrent devices used in transformer circuits. Lab activities are used to reinforce theory.