Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

rare-earth permanent magnet
magnet made of compounds of iron, nickel, and cobalt with one or more of the rare-earth elements such as samarium. These materials combine the high residual flux density of the alnico-type materials with greater coercivity than ferrites.
residual magnetism
a form of permanent magnetism, referring to the flux remaining in a ferromagnetic material after the MMF that created the flux is removed. For example, if a bar of steel is surrounded by a coil and current is applied to the coil, the steel bar will create a magnetic field due to the rotation of the domains in the steel. After the current is removed, some of the domains will remain aligned, causing magnetic flux.
saturation magnetization
the magnetic moment per unit volume of a material when the magnetization in the sample is aligned (saturated) by a large magnetic field.
self-demagnetizing field
a field inside of a permanent magnet that is opposed to its own magnetization, which is due to internal coupling of its poles following the introduction of an air gap in the magnetic circuit.
superparamagnetism
a form of magnetism in which the spins in small particles are exchange coupled by may be collectively switched by thermal energy.
unbalanced magnetic pull
a phenomenon in electric machines arising from the rotor not being symmetrical with respect to the stator or the axis of the rotor and stator not being coincident. Results in a higher pulling force on the side with the smaller airgap, resulting in additional bearing stresses.
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