Transformer nameplate has a parameter called "impedance voltage," which is usually a percentage between 5 and 10, it is the transformer secondary winding short circuit, the primary winding voltage slowly increase, when the secondary winding short-circuit current reaches the rated current, the primary winding applied voltage (short-circuit voltage) and rated voltage ratio percentage.
The formula is: Uk%= short-circuit voltage/rated voltage *100%.
This is the simplified equivalent circuit of the transformer, Rs is the resistance inside the transformer, Xs is the reactance inside the transformer, Zs is used in the figure to represent the impedance of the whole transformer. Z'L is the equivalent impedance from the load side to the primary side.
According to the meaning of impedance voltage, short-circuit the secondary winding, that is, Z'L is equal to 0, and then slowly pressure the primary winding, until the current of the secondary side is equal to the voltage value of the rated current of the secondary side of the transformer, which is the short-circuit voltage value we need. Then it is easy to know the impedance voltage value according to the previous calculation.
In the actual test process, with the help of professional test equipment, according to the principle of impedance voltage, short circuit voltage can be easily measured, so as to calculate the value of impedance voltage.
What is the use of impedance voltage?
Impedance voltage is an important parameter of transformer, which is related to many factors of transformer, such as: capacity, copper loss, iron loss, coil material and structure, etc.
It is related to the stability of the power supply system, the power supply quality of the load, the safety and reliability of the parallel transformer and so on.
Calculate the maximum short-circuit current that transformer can withstand according to impedance voltage
