ABSTRACT
Today, both the IEEE term ‘‘load tap changer (LTC)’’ and the IEC term ‘‘on-load tap-changer (OLTC)’’
are in the terminology of international standards, but the term ‘‘load tap changer (LTC)’’ is used
primarily in this chapter. Load tap changers are one of the indispensable components for the regulation
of power transformers used in electrical energy networks and industrial application. This contribution
explains the technological developments of resistor-type LTCs as well as of reactor-type LTCs. The
general switching principles for LTCs are discussed and applications of LTCs are introduced. Today’s
design concepts of LTCs are described including the new generation of vacuum-type LTCs. The vacuum
switching technology-used in LTCs-is the ‘‘state-of-the-art’’ design at the present time and for the
foreseeable future. Examples of LTC designs and the associated switching principles show the variety of
the use of vacuum interrupters.
