The through-core Electrical Current Transformer does not have a primary winding in its own structure. The current-carrying (load current) wires from L1 to L2 pass through a circular (or other shape) iron core made of silicon steel sheet rolling to serve as a primary winding. The secondary winding is directly and evenly wound on the circular iron core, and is connected in series with the secondary load of the current coil such as meters, relays, and transmitters to form a closed loop. Different transformation ratio Electrical Current Transformer. This type of Electrical Current Transformer has the same core and primary winding, while the secondary winding is divided into two independent windings with different turns to meet the needs of different transformation ratios and different accuracy levels under the same load current. .