, double-winding transformer is the most common contact with the transformer, commonly used distribution transformers below 35KV are usually Double winding transformer.
The exact definition of a three-winding transformer: a transformer with three windings per phase that are independent on the circuit (the circuit and not the magnetic circuit! ). It can be thought of as consisting of three pairs of double-winding transformers.
Three-winding transformer voltage, voltage ratio, short-circuit impedance and other characteristics: three-winding transformer has three different voltages, there are three voltage ratios: K12 = N1/N2, K13 = N1/N3, K23 = N2/N3; similarly there are three short-circuit impedance: Z12, Z13, Z23.
Three-winding transformer application range:
Transformer above 110KV (the most widely used is the large transformer of 220KV and above. For example: SFSZ9-180,000/220/121/38.5, the third letter S means "three windings");
35KV rectifier transformer (at this time the second and third windings are usually the same voltage, each 50% of the capacity).
Three-winding transformer structure: in order to meet the short-circuit impedance requirements, the concentric position of the three windings can be different, from the outside to the inside can be high, medium and low arrangement, or high, low and medium arrangement.