What Is The Cause Of Transformer Overcurrent?

If the so-called overcurrent refers to the overcurrent of the transformer input current, there may be the following reasons:

　　 1. The transformer is saturated. As we all know, the transformer winding will be inductive under alternating current, its alternating impedance is large, and its impedance is proportional to the permeability. At the same time, magnetic materials have a saturation magnetic flux density. If the transformer is not properly designed or the bias occurs, the working magnetic density of the transformer will be too high. When it is greater than the saturation magnetic density, the magnetic permeability will drop to 0. The remaining resistance is equivalent to directly connecting the positive and negative poles of the power supply to a wire, and the consequences can be imagined. In the switching power supply, this phenomenon often occurs in the push-pull topology. Generally, a capacitor is connected in series on the primary side to solve the magnetic bias problem.

　　 2. Load short circuit! !

　　3. The insulation of the transformer windings is not done well, and there is a short circuit between turns or the primary and secondary windings.

　　4. Some core material characteristics, for example, the design does not consider the influence of DC bias and temperature on the permeability. Under high temperature and high DC bias, the impedance of the transformer winding is reduced and overcurrent occurs.