Transformer with three windings. The dots show the relative configuration of the windings.
Transformer with electrostatic screen preventing capacitive coupling between the windings.
Various types of electrical transformer are made for different purposes. Despite their design differences, the various types employ the same basic principle as discovered in 1831 by Michael Faraday, and share several key functional parts.
^G. Volkert, K.-D. Frank (1972) "Metallurgie der Ferrolegierungen", page 131, Springer Verlag, Berlin, Heidelberg, New York ISBN978-3-642-80580-6