Continuously Transposed Conductor (or CTC) is the most used for power transformer windings.
It consists of a group of enamelled rectangular wires, usually with PVF enamel, which are stranded to create a rectangular rope.
In this group each strand successively and repeatedly takes on every possible position inside the whole conductor cross-section.
The strands as a whole are wrapped with pure cellulose paper tapes.
This conductor is used for manufacturing low losses windings for electric machines.