Lecture 3 - Soft Magnetic Materials Flashcards
What are the desired properties of soft magnetic materials?
They need to be reversible.
They have a coercive force of zero.
They have minimal loss (no loss).
No loss is obtained by having a small enough hysteresis loop that it looks like a straight line, therefore it has a small enclosed volume and thus a small loss per cycle
What are forms of losses in soft magnetic materials?
Core losses, scaling with (AC) frequency
Eddy Current losses, scaling with frequency ² and inversely proportional to resistivity ρ
Magnetostriction, where when an external field is applied on the material, the crystals attempt to align with it leading to the material trying to change its shape to move domains with different preferential directions to align with the field.
How do we minimise losses in soft magnetic materials?
Eddy losses follow the equation:
P = B²t²f²/ρ
where t the thickness of a thin sheet of magnet.
1) Therefore we want to have a small coercive field Hc.
2) A large resistivity ρ and thus high resistance R.
3) Large saturation magnetisation Ms.
