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.
