The so-called over-current, if it refers to the transformer input current over-current, may have the following reasons:
1. transformer saturation, as we all know, transformer windings in the AC will show perceptual, and its AC impedance is larger, and its impedance size and permeability is proportional to. At the same time, the magnetic materials have saturation flux density, improper design or if the transformer magnetic bias will make the transformer magnetic flux density is too high, when greater than the saturation magnetic flux density, magnetic permeability dropped to 0, then only the basic AC impedance transformer impedance, the equivalent power supply directly to the negative electrode is connected to a wire, the consequences as can be imagined. In switching power supply, this phenomenon often occurs in push-pull topology, which usually solves the magnetic bias problem at the primary side of series capacitor.
2. load short circuit!!
3. transformer winding insulation is not done, there is an inter turn short circuit or a former side winding short-circuit.
4. some core material characteristics, such as design without considering the influence of DC bias and temperature on permeability, under high temperature and high DC bias, leads to lower impedance of transformer windings and over-current.
What are the advantages of an autotransformer in comparison with an ordinary transformer?
1, how to use the transformer silicon steel and copper wire and winding capacity has a direct relationship, and the winding capacity of the autotransformer is lower than ordinary transformer, which makes use of the self coupling transformer silicon steel and copper wire less, thus reducing the cost;
2, because of the autotransformer than ordinary transformer materials less than that of silicon steel sheet and copper wire, flux density and current density in the same time, since the copper loss and iron loss in transformer are less, so that improve the efficiency of;
3. The volume and weight of autotransformer are much smaller than that of ordinary transformer. Therefore, it is more convenient and easier to install self coupling transformer for high and low voltage equipment;
4, the different transportation conditions so that the transformer manufacturing capacity limit, and autotransformer transportation than ordinary transformer is more simple and quick, which makes its manufacturing capacity limit is much larger than ordinary transformer.