Why Is Impedance Important When Specifying A Transformer?

Transformer such as the oil immersed transformer, it is important electrical equipment, in the process of use to enhance the use of the transformer and efficiency of continuous improvement, because the voltage of the transformer is affected by many factors, the voltage control, use and adjust the pressure is not the same. The impedance of short circuit to transformer is also a main reason that affects transformer work, and it is also one of the most effective means to control voltage. Then in the actual operation and work, the transformer's short-circuit impedance is what mean, here we give you a detailed introduction:

In general, the short-circuit impedance of a transformer refers to the equivalent series impedance Zk=Rk+jXk between the terminals of a pair of windings at the rated frequency and the reference temperature. As its value is determined by load test in addition to calculation, it is customarily called short circuit voltage or impedance voltage.

Oil Immersed Transformer

Why is impedance important when specifying a transformer?

Impedance is a very important specification. First, it affects the maximum short-circuit current that the transformer can deliver; the higher the impedance, the lower the maximum short-circuit current. Second, it also affects the voltage regulation of the transformer; the higher the impedance, the lower the voltage regulation over the transformer's load range. A common misconception; there is no direct relationship between impedance and efficiency. Manufacturers typically list a range of impedances that their transformers will meet, and customers can also specify specific impedances, although this may affect cost.

Influence of transformer short-circuit impedance on transformer operation:

Transformer short-circuit impedance is also called impedance voltage, in the transformer industry is defined as follows: when the transformer secondary winding short-circuit (steady-state), the primary winding flow rated current and applied voltage are called impedance voltage Uz. Usually Uz in the percentage of rated voltage, that is, Uz =(Uz/U1n)*100%

When the transformer runs at full load, the short-circuit impedance has a certain influence on the output voltage of the secondary side. The short-circuit impedance is small, the voltage drop is small, the short-circuit impedance is large, the voltage drop is large. When the transformer load appears short circuit, the short circuit impedance is small, the short circuit current is large, the transformer bears the electric power is big. The short circuit impedance is large, the short circuit current is small, the transformer bears the electric power is small.