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Analysis Of Advantages And Disadvantages Of Autotransformer
- Nov 06, 2017 -

Autotransformer with the ordinary double-winding transformer has the following advantages:


1) Consumption of materials, low cost. Because the amount of silicon steel sheets and copper wires used in transformers is related to the rated induction potential and rated current of the windings, that is to say to the capacity of the windings, the capacity of the autotransformer windings is reduced, the material used is also reduced and the costs are also low.


2) Loss less effective. Due to the reduced amount of copper wire and silicon steel sheet, the copper loss and iron loss of the autotransformer are less than that of the double-wound transformer at the same current density and flux density, so the benefit is higher.


3) Easy to transport and install. Because it than the same capacity double winding transformer light weight, small size, small footprint.


4) Improve the transformer's manufacturing capacity limit. Transformer limit manufacturing capacity is generally limited by the conditions of transport, the same transport conditions, under the same conditions of transport, autotransformer capacity than double-winding transformer manufacturing larger.


The use of autotransformers in power systems can also have adverse effects. The disadvantages are as follows:


1) Increase the power system short-circuit current. Due to the electrical connection between the high and medium voltage windings of the autotransformer, the short-circuit impedance of the autotransformer is only (1-k / 1) square of the common double-winding transformer. Therefore, after the autotransformer is used in the power system, So that three-phase short-circuit current increased significantly. And because the autotransformer neutral must be directly grounded, so the system will greatly increase the single-phase short-circuit current, and sometimes even more than three-phase short-circuit current.


2) Cause some pressure on the pressure. Mainly due to its high, medium voltage winding power caused by the current auto transformer may have three ways of regulating the voltage, the first is installed within the autotransformer winding with a load to change the position of the tap changer device; The two are in the high-pressure and medium-voltage lines to install additional transformers. However, these three methods are not only difficult to manufacture, uneconomical, but also have disadvantages in operation (such as affecting the voltage of the third winding) and are not idealized.


3)The winding over-voltage protection complex. Due to the coupling of high and medium voltage windings, the amplitude of the overvoltage surge on the other side may exceed this level of insulation when either side falls into a lightning surge of an amplitude corresponding to that of the winding. In order to avoid the occurrence of this phenomenon, it is necessary to install a set of valve arresters on the outlet ends of the high and medium voltage sides.


4) Make relay protection complicated.


Although autotransformer has some shortcomings, all countries attach great importance to the application of autotransformer, which is mainly inseparable from the development of high-voltage and high-voltage power system. With the increase of capacity and voltage, The advantages of the transformer transformer is even more prominent.