DC magnetic bias refers to the appearance of DC component in transformer excitation current, which leads to half-cycle magnetic saturation of transformer core, and thus causes a series of electromagnetic effects.

2, transformer normal working condition

Under the condition of AC overexcitation, the flux density of transformer increases and the excitation current is distorted. The transformer works near the nonlinear region of magnetization curve, and the excitation current waveform is sharp wave, and the positive and negative half waves are symmetrical. Under DC bias, DC and AC magnetic flux are superimposed, and the saturation of the half-cycle iron core in the same direction as DC bias increases, while the saturation of the other half-cycle decreases, and the corresponding excitation current waveform presents an asymmetric positive and negative half-wave shape.

3, transformer magnetic bias phenomenon

The smaller DC component will form a larger DC excitation potential in the winding, which will act on the primary side of the transformer together with the AC magnetic potential, so that the working magnetization curve of the transformer core will shift, resulting in asymmetry about the origin, that is, the transformer magnetic bias phenomenon.

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