# Can a transformer be used with direct current

FAQ | Feb 10,2023

The answer is no. A transformer is not used with direct current. Because the transformer itself is to use the alternating magnetic field to achieve the transmission of energy.And pulsating voltages with DC components do not work. Because the direct current will saturate the magnetic circuit of the transformer, lose the ability of “AC transformer”. If DC current cannot be transformer, the reason is because DC current does not change the magnetic field. What if you have an unsteady current? An unsteady current, if the Fourier transform is expanded, is a constant DC plus a number of AC’s, so in this combination, the DC part can’t change voltage, but the AC part can. But the premise is that the transformer core is large enough, otherwise DC will let the core magnetic saturation, so that the AC part of the change does not produce magnetic field changes. The coil with DC current only generates an automatic voltage induction potential opposite to the current at the moment of power-up and changes in magnetic field induction, and the magnetic field becomes stable after the DC is stabilized.

In addition, from the actual structure of the transformer, because the winding resistance of the transformer is generally relatively small, if the direct current is entered, its frequency is f=0, so it will produce a large amount of current. In a short time, a large amount of heat will be generated inside the voltage tester. If the time is a little longer, the heat generated by the current is enough to burn out the voltage tester.

So,to sum up,a transformer can not be used with direct current.

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