Theory and Principles
DOI link for Theory and Principles
Theory and Principles book
Transformers are devices that transfer energy from one circuit to another by means of a common magnetic field. In all cases except autotransformers, there is no direct electrical connection from one circuit to the other. The use of a magnetic field from one coil to induce a voltage into a second coil is the principle on which transformer theory and application is based. Some small transformers for low-power applications are constructed with air between the two coils. Steel cores were used in power transformers when alternating current circuits for distribution of electrical energy were first introduced. When voltage is applied to the exciting or primary winding of the transformer, a magnetizing current flows in the primary winding. This current produces the flux in the core. The flow of flux in magnetic circuits is analogous to the flow of current in electrical circuits.