| PERMANENT MAGNETIC MATERIALS |
| INDUSTRIAL MAGNETIC DEVICES |
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| MAGNET TERMINOLOGY GLOSSARY |
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The terms have been compiled to assist you with sharing information, experience, and knowledge.
Magnetic Circuit:
An assembly consisting of some or all of the following:permanent
magnets, ferromagnetic conduction elements, air gaps,electrical
currents.
Magnetic Flux, Ø:
The total magnetic induction over a given area. When the
magnetic induction, B, is uniformly disributed over an
area A, ?=BA. The general equation is ?=B. dA.
Magnetizing Force, H:
The magnetomotive force per unit length at any point in
a magnetic circuits. Measured in oersteds in the cgs system.
Magnetomotive Force, F:
Analogous to voltage in electrical circuits, this is the
magnetic potential difference between any two points.
Maximum Energy Product, BHmax:
The point on the Demagnetization Curve where the product
of B and H is a maximum and the required volume ofmagnet
material required to project a given energy into its surroundings
is a minimum. Measured in Mega Gauss Oersteds, MGOe.
North Pole: That
pole of a magnet which, when freely suspended, would pointto
the north magnetic pole of the earth. The definition of
polarity can be a confusing issue, and it is often best
to clarify by using "north seeking pole" instead
of" north pole" in speciications.
Oersted, Oe:
A cgs unit of measure used to describe magnetizing force.
The English system equivalent is Ampere Turns per Inch,
and the SI system's is Ampere Turns per Meter.
Orientation Direction: The
direction in which an anisotropic manet should be magnetized
in order to achieve optimum magnetic properties. Also
knownas the "axis"," easy axis", or"angle
of inclination".
Paramagnetic Material:
A material having a permeability slightly greater than
1
Permeance:
The inverse of reluctance, analogous to coductance in
electrical circuits.
Permeance Coefficient, Pc:
Ratio of the magnetic induction, Bd, to its self demagnetizing
force, Hd. Pc=Bd/ Hd. his is also known as the "load
line" oroperating point of the magnet, and is useful
inestimating the flux output of the magnet, and is useful
in estimating the flux output of the magnet in various
conditions. As a first order approximation, Bd/Hd=Lm/Lg,
where Lm is the length of the magnet, and Lg is the length
of an air gap that the magnet is subjected to. Pc is therefore
a function of the geometry of the magnetic circuit
Pole Pieces:
Ferromagnetic materials placed on magnetic poles used
to shape and alter the effect of lines of flux.
Relative Permeability , µr:
The ratio of permeability of a medium to that of a vacuum:µr
=µ/µ0. In the cgs system,µ0 =1 in a
vacuum by definition. The permeability of air is also
for all practical purposes equal to 1 in the cgs system.
Reluctance, R:
Analogous to resistance in an electrical circuit, reluctance
is related to the magnetomotive force, F , and the magnetic
flux, ? by the equation R=F?, (paralleling Ohm's Law)where
F is the magnetomotive force, and ? is the magnetic flux,
(in cgs units).
Remenance, Bd:
The magnetic induction which emains in a magnetic circuit
after the removal of an applied magnetizing force. If
there is an air gapin the circuit, the remanence will
be less than the residual induction, Br.
Residual Induction, Br:
This is the point at which the hysteresis loop crosses
the B axis at zero magnetizing force, and represents the
maximumflux output from the given magnet material. By
definition, this point occurs at zero air gap, and therefore
cannot be seen in practical use of magnet materials.
Return Path:
Conduction elements in a magnetic circuit which provide
a low reluctance path for the magnetic flux
Reversible Temperature Coefficient:
A measure of the reversible changes in flux caused by
temperature variations.
Saturation:
The condition under which all elementary magnetic moments
have become oriented in one direction. A ferromagnetic
material is saturated when an increase in the applied
magnetizing force produces no increase in induction. Saturation
flux densities for steels are in the range of 16,000 to
20,000 Gauss.
Stabilization:
Exposure of a magnet to demagnetizing influences expected
to be encountered in use in order to prevent irreversible
losses during actual operation. Demagnetizing influences
can be caused by high or low temperatures, or by external
magnetic fields. |
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