Magnetic Circuits - B-H Relationship (Magnetization Curve)

[legobuildingsrewiew]

These videos are really amazing. They help me out a lot as a student.

[Greg_Chase]

Actually, it might be worth pointing out the 'mu r', the relative permeability, of a saturated ferro core material ALSO drops to about 1, so when the core of an inductor or transformer saturates, the permeability drops to that of free space, mu naught.

This drop in permeability to that of free space when a core saturates is used in a device called a 'magnetic amplifier', so-named because it is PURPOSELY made to reach magnetic saturation in order to amplify the AC or RF in its 2nd winding.

The magnetic amplifier has a 1st winding fed by a DC current. When the DC is "off", the 2nd winding - an AC or RF coil - encounters the normal permeability of the magnetic core and the normal hysteresis (the normal 'resistance' of re-arranging the magnetic domains in the core material as the AC reverses direction during each cycle).

But when the DC is turned on to the 1st winding, the core saturates, the permeability of the core drops to near-free space, and the impedance to the AC DROPS, which amplifies the AC. It's called a 'magnetic amplifier' NOT because it amplifies magnetic fields, but because it uses full magnetization of the core to amplify the AC current in the 2nd winding.

This device is also called a "saturable reactor". Most EE types were trained that 'core saturation is to be avoided' but the magnetic amplifier has been around for decades. It's just a bit rare.

[sing]

thank you so much for the wonderful explanation ... wonderful video lecture

[Dragon-Slayr]

Mag curve was to get through the dry leaves