By Sunny | 23 July 2019 | 0 Comments

Effect of Transformer on Short Circuit Impedance

Leilang-Electric is located in Shanghai,China.We are specialized in manufacturing all kind of low voltage transformer,three phase transformer,single phase transformer, variac transformer,voltage stabilizer, ac stabilizer,power regulator, reactor, etc.
When the transformer is fully loaded, 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 and the voltage drop is large. When the transformer load is short-circuit, the short-circuit impedance is small, the short-circuit current is large, and the transformer bears large electric power. The short-circuit impedance is large, the short-circuit current is small, and the transformer bears less electric power.
The so-called short-circuit impedance is the resistance formed by short-circuit of electrical appliances, such as eddy current. The short-circuit impedance of transformer refers to the equivalent series impedance Zk=Rk+jXk between terminals of a pair of windings at rated frequency and reference temperature. Because its value is determined by load test besides calculation, it is also called short circuit voltage or impedance voltage.
We have all learned physical knowledge, the current-carrying conductor in the magnetic field will bear the effect of mechanical force, so when the transformer winding passes through the current, but because of the effect of current and leakage magnetic field, the electromagnetic mechanical force will be generated in the winding. Its magnitude depends on the magnetic flux density of the magnetic leakage field multiplied by the current of the conductor. We also know that the direction of departure depends on the left hand. When the transformer operates under normal load, the force acting on the conductor is relatively small, but when sudden short circuit occurs, the maximum short circuit current will be 25-30 or greater than the rated current. However, according to the formula, the electromagnetic force between windings and the square of the short circuit current will be generated when short circuit occurs. In direct proportion, the mechanical force in short circuit will be more than several hundred times more than that in normal operation, and this force will produce very fast. In such a short time, the short circuit can not cut off the circuit.
Transformer short-circuit impedance, also known as impedance voltage, is defined in the transformer industry as follows: when the secondary winding of the transformer is short-circuit (steady state), the voltage applied by the rated current of the primary winding is called impedance voltage Uz. Uz is usually expressed as a percentage of the rated voltage, i.e. uz= (Uz/U1n)*100%
In a word, under the action of huge short-circuit electromagnetic force, many parts of transformer winding may be damaged. So when designing transformer, manufacturers must study the endurance ability of transformer in short-circuit electrodynamic force and the mechanical strength of winding in short-circuit condition to check, in order to ensure the normal operation of transformer. In operation, we must consider the force of transformer.
When the transformer is fully loaded, 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 and the voltage drop is large. When the transformer load is short-circuit, the short-circuit impedance is small, the short-circuit current is large, and the transformer bears large electric power. The short-circuit impedance is large, the short-circuit current is small, and the transformer bears less electric power.
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