Transformer Uk = 4.5% What does it mean?
Transformer short-circuit impedance, that is, his own impedance. The impedance is large, the transformer needs to resist the short circuit current multiplier is small, relatively speaking, anti-short circuit capability, but the transformer's external characteristics (volt-ampere characteristics) soft (with the transformer output current increases, the output voltage - transformer Voltage drop is very powerful). On the contrary, short-circuit impedance is small, the transformer needs to resist the short-circuit current multiplier, requiring a strong anti-short circuit transformer capacity. Of course, the external characteristics of the transformer better.
Another short-circuit impedance will also affect the transformer manufacturing costs. He is not the bigger the better, nor the smaller the better. To be considered, so there are strict rules in the national standard.
Uk represents the transformer impedance voltage, refers to the transformer short-circuit impedance voltage. The impedance of the transformer (now the standard is called: "short-circuit impedance") standard value with a percentage (per unit value) to represent.
General small distribution transformer standard value of 4% or 4.5%.
The short circuit impedance of the transformer is related to many factors of the transformer. Such as transformer capacity, loss, internal coil structure and so on. But once the transformer is manufactured, it is the same.
Short-circuit impedance is a very important technical indicator for the user. Such as the stability of the power supply system, the quality of the power supply, the transformer in parallel after the safety and reliability, and so have a relationship.
