T connection

a.1.(Elec.) The connection of two coils diagrammatically as a letter T, chiefly used as a connection for passing transformers. When the three free ends are connected to a source of three-phase current, two-phase current may be derived from the secondary circuits. The reverse arrangement may be used to transform from two-phase.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.