What is “Exciting Current (No-Load Current)”?

Current which flows in any winding used to excite the transformer when all other windings are open-circuited. It is usually expressed in percent of the rated current of a winding in which it is measured.

A transformer will always consume a small amount of current to energize the windings even if there is no load. This energizing current can create a large inrush several times the transformer’s rated current for a few cycles during initial energization before it reduces to a much lower steady draw.