Core Magnetization

Magnetic materials are composed of areas called “magnetic domains” which are randomly oriented small magnets. In the presence of an MMF source like a wire of N turns carrying I, the magnetic domains align themselves with the magnetic field.

BH Curve

The BH curve of a non-magnetic material is linear with a very small slope.
The BH curve of a ferromagnetic material is nonlinear with a large slope.

In the BH curve of a ferromagnetic material, three distinct regions can be identified:

• Linear region (large and constant mu)
• Saturation region (increasing H does not really increase B)
• The knee of saturation (The region between 1 and 2) $B=\mu H=\frac{\varphi }{A}$

Example Curve

Hysteresis

Exciting a core to create a permanent magnetic is caused by Hysteresis

Eddy Current Loss

See Eddy Currents

Power Loss

$P_{hysteresis}=K_{h}V{B}_{\max }^{n}f$ $P_{eddy}=K_{e}V{\left(B_{\max }tf\right)}^2$ Where:

• $k_h$ = constant
• V = volume of magnetic material
• $B_{\max }$ = peak value of magnetic flux density

The total core loss is obtained by summing these two losses.