How to reduce inrush current in transformer

FAQ | Feb 24,2023

Transformer inrush current refers to the transient current caused by the change of magnetic field in the core when the transformer is switched on for the first time. These inrush currents can cause noise and vibration in the transformer and may interfere with other electrical equipment, so they need to be suppressed.
The following are some ways to suppress the transformer inrush current:
Series resistance: A resistor is connected in series at the input end of the transformer to limit the inrush current. However, this method results in energy loss, and appropriate resistance values need to be selected to ensure the safety of the circuit.
Series inductor: Series an inductor at the input end of the transformer can form a low pass filter, which can suppress high frequency noise and interference. However, this method also results in energy loss and requires the selection of appropriate inductance values to ensure the stability of the circuit.
Premagnetization: Before the transformer is powered on, a small power supply can be used to premagnetize the core of the transformer by providing a certain amount of current, thus reducing the size of the inrush current. This method requires an additional power supply and control circuit, but can reduce the size of the inrush current.
Phase shift: The inrush current can be reduced by changing the phase difference between the input voltage and the output voltage of the transformer. This method requires an additional phase shifter, but can effectively reduce the inrush current.
It is necessary to choose the appropriate method to suppress the transformer inrush current according to the specific situation.


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