Causes of transformer surge current

Transformers play a role in electrical systems It plays an important role and its working principle is to transfer electrical energy from one circuit to another through mutual inductance. When the transformer is reconnected or disconnected from the mains, a brief voltage spike occurs, which is known as an inrush current.

Surge current is caused by sharp changes in the magnetic field of the transformer, causing current to move in the windings. These currents can reach more than twice the rated current of the transformer, potentially causing damage to equipment and circuits. Therefore, in actual electrical systems, measures need to be taken to limit the impact of surge current, such as adding capacitors, resistors, inductive reactance components, etc.

How to reduce transformer surge current

Transformer surge The current is caused by the energization of the transformer and usually occurs in one of the windings of the transformer, in most cases the primary winding. This occurs when the primary of the transformer draws the maximum instantaneous current. This occurs when the secondary of the transformer is open circuit (not When connected to a load), this surge current will not produce any permanent fault, but will cause unnecessary switching of breakers in the circuit.

There are several ways to reduce the inrush current due to the resistor value High, traditional methods cannot be used, so using newer methods, through the use of power quality standards and reconstruction of the power system will force power companies to reduce the amount of inrush current:

Reduce inrush current by using a starting resistor

Due to the unbalanced nature of the inrush current, the inrush current will flow towards the transformer neutral point , by using a series resistor at the zero point of the transformer, it will behave as a starting series resistor and will improve the inrush current reduction.

When the three phases of the transformer are turned on at the same time, you can see that the surge current is greatly reduced. When the three phases of the transformer are not turned on at the same time, the surge current will be greatly reduced.

The surge current is due to the change of magnetic flux in the transformer core, which Depending on the network voltage, we can use some parameters such as inductance, resistance, etc. to reduce the transient magnetic flux of the transformer, which will lead to a reduction in inrush current.

Some common solutions to reduce inrush current

It can reduce the hysteresis flux of the transformer.

Switch on the transformer at the voltage peak.

Increase frequency when switching.

Reduces the voltage during switching.