The transformer winding is the internal circuit of the equipment, which is directly connected with the external power grid, and it is the most important part of the transformer. The winding is often called the "heart" of a transformer. The change of winding turns can change the voltage. When the winding is combined with the core, that is the transformer itself makes up of the electromagnetic induction system, we can get the required voltage and current.
The transformer for depressurization can be used as a step-down transformer, but the step-down transformer of the power system can not be used as a step-up transformer, and the step-up transformer can not be used as a step-down transformer. An important parameter of the transformer is the number of turns per volt, that is how many turns should have in one volts. After the voltage is determined, the number of turns is also determined. But transformers have losses. When twining the winding, the number of coils in two turns is 5% more than the one time turns. That is, the voltage of the two times is 5% more than one time turns.
Such as the step-down transformer, the one time turns is a high voltage and the two time turns is a low voltage. If it is used for boosting, the low voltage is the one time and the high voltage is the two time, and the coil of high voltage should be 5% more than the low voltage. But in fact, the coil of low voltage is 5% higher than the coil of high voltage. The number of coil of the high voltage is 10% less than the number of coils in theory and the voltage is also 10% less than the voltage in theory. And the rated voltage is not reached.