Control transformers are specific types of separation transformers, designed and used to supply power to control circuits, such as signaling, control, and interlocking systems, etc.

In the event of a fault, they reduce the short-circuit current value. They also allow the use of auxiliary circuits without grounding.

Limited power ratings and voltage drops, along with a high capacity to withstand strong inrush currents, are the main qualities of these products, regulated by EN61558-2-2 standards.