What is Magnetic Saturation?

Definition of Magnetic Saturation
Magnetic Saturation of Iron
Now if we try to work with flux density above this limit, the iron exhibits higher reluctance compared to that at low flux density. As a result the said iron or steel does not behave like good conductor of magnetic flux. At that situation much more mmf is required to drive the flux through the same iron core. More mmf means more ampere turn in the case of electromagnetic, hence this situation should avoid.
Relation between Reluctance and Flux Densitymagnetic saturationIn the above figure it is seen that, when flux density is within limit, the reluctance of the magnetic path is quite low but when it crosses certain value such as 2 Tesla as shown here, the reluctance of the same magnetic path is sharply increased.
To avoid the undesirable effect of the magnetic saturation, the size of the iron core suitably chose for a particular engineering application.
Generally volume of the iron or steel core of magnetic path in a machine is so chosen that flux density of the core does not cross the limit of 1.5 Tesla in normal operating conditions.
The unit beyond which magnetic flux density in a magnetic area does not increase sharply further with increase of mmf.
It is well known to us that iron has very little reluctance. It is much smaller than reluctance of air. But above statement is only true when magnetic fluxdensity is an iron core is less than specific limit. This limit may be from 1.6 to 1.8 Tesla depending upon the particular magnetic steel or iron in question.
The graph below is shown the relation between effective reluctance of a magnetic material such as iron and its corresponding flux density.
As density of any quantity is related with volume, hence by increasing the cross section (i.e. volume) of the magnetic path one can reduce the effective flux density of the path for same given mmf.

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