PCB transformer leakage inductance can be how big

Transformer leakage inductance is large, there are two cases:

1, the transformer is not properly designed, the magnetic flux density is large, resulting in leakage of magnetism, so that the transformer iron loss increases, in general the leakage inductance of the transformer is the smaller the better.

2, special requirements of the transformer, such as welding transformers, in order to obtain a decline in output characteristics, deliberately in the magnetic circuit of the transformer to add magnetic shunt, increase the leakage of magnetism, in order to obtain the appropriate, declining output characteristics.