Why does saturation of a ferromagnetic result in non-sinusoidal current?

[tonyjk]

Hello... I have a question: Physically why when a ferromagnetic is saturated the current is non-sinusoidal ( I'm taking the example of the magnetising current of a transformer). I know graphically and mathemeticalty why( from the hysteresis loop) but In reality what happens(I'm talking about magnetic field or/and electric field) . I know the magnetic domain of the iron core will be aligned etc... but why there's a non-sinusoidal current... Thanks

 

[NascentOxygen]

The principle of an inductor is that it surrounds its coils with a magnetic field (that field being produced by the current in the coils). So any change in current in the coils induces a voltage in the coils and this voltage tends to oppose the change in current that produces it. Ideally, there exists a linear relationship between the current and the field.

Around those peaks where the core starts to saturate (i.e., show non-linear behaviour), a further increase in current fails to produce the full expected change in the magnetic field, this in turn induces less opposing voltage to oppose that current, with a consequence that the current is able to increase more than for expected linear behaviour.