ABSTRACT
This chapter discusses the role of a load tap changer (LTC). The flicker of the house lights while having dinner is a sign of an LTC. An LTC is a device that connects different taps of the tapped windings of transformers without interrupting the load. An LTC is made up of four elements: selector, changeover switch, transition mechanism and driving mechanism. There are two generic types of tap changers: in-tank tap changer and separate-compartment type. The chapter illustrates the main types of regulation: linear switching, reversing-type regulation, coarse–fine regulation and bias-winding type. An LTC must be capable of switching from one tap position to another without interrupting the flow of current to the load at any time. Autotransformers with tap changers present special challenges for transformer designers. A phase-shifting transformer is ideally a transformer with a 1:1 voltage ratio that also has the ability to change the phase angle of its output voltage relative to its input.
