Magnetic Materials

Magnetic Material

Flux density B density of magnetic field flowing through a given area of material

Flux intensity H Intensity of magnetic field due to interaction of B

Ferromagnetic material – electrical steel which is usually used for motor construction

Ferromagnetic material

Hysteresis loop is formed by applying sinusoidal excitation of different amplitude and plotting B versus H

For common electrical steel hard saturation reaches at flux density between 1.7 to 2.3T

Core losses

When ferromagnetic material are excited with any time varying field, energy is dissipated due to hysteresis and eddy current losses

Hysteresis loss results because energy lost in every time a hysteresis loop traversed

Loss is directly proportional to size of the loop.

Eddy current loss is caused by electric current induced within ferromagnetic material under time varying excitation. This induced ferromagnetic material circulated within material and dissipate as heat.

Eddy current loss can be minimized by increasing resistivity of material. Electrical steel contains small amount of silicon, which increases resistivity of material. Another way is to use laminated sheet to increase resistivity. Thin lamination is required to reduce eddy current losses.