Time:2026-08-31 Browse: 12
The working principle of a current transformer (CT) is based on Faraday's law of electromagnetic induction. It couples a primary winding, which has few turns and is connected in series with the main circuit, to a secondary winding with many turns that connects to measuring instruments, via a closed iron core with high magnetic permeability. When a large current under measurement flows through the primary winding, an alternating magnetic flux is generated in the core, inducing an electromotive force in the secondary winding. Since the secondary circuit is approximately short-circuited, this induces a standardized small current (5A or 1A) proportional to the primary current (inversely proportional to the turns ratio). This transformation relies on excitation current to establish the magnetic flux; however, non-ideal factors such as core saturation introduce errors. Therefore, in practical applications, it is essential to strictly prevent open circuits on the secondary side and to properly select CT models to avoid saturation.
