The focus is on the function and circuitry of power transformers and their special designs, including control, auxiliary, savings, Scott, and rectifier transformers. The operation of the transformer is explained unconventionally through magnetization phenomena, and its theory is described based on stationary and non-stationary operating behavior. The discussion also covers the lifespan-determining heating of the transformer and the mathematical foundations for calculating unsymmetrical loads using symmetrical components. Key topics include the generation and effects of harmonic currents and voltages in connection with non-sinusoidal load currents. Transformer protection is discussed in detail, and the conclusion covers measurement acquisition through converters.