When the transformer has an overcurrent situation, we have summarized several common reasons that may occur.
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 winding of the transformer will be inductive under alternating current, and 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 biased, the working magnetic density of the transformer will be too high. When the magnetic density is greater than the saturation magnetic density, the magnetic permeability will drop to 0, and the AC impedance of the transformer is basically only 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 bias problem.
2. Load short circuit!
3. The insulation of transformer windings is not done well, and there is a short circuit between turns or the primary and secondary windings.
4. The characteristics of some magnetic core materials, for example, the design does not consider the influence of DC bias and temperature on permeability. Under high temperature and high DC bias, the impedance of the transformer winding is reduced and overcurrent occurs.