Anisotropic-They are magnets that have an easy axis of magnetization, so that the magnetic characteristics are optimal in one direction.
Air Gap-the air or nonmagnetic material between magnetic poles.
B (Magnetic Induction)-is the magnetic flux per unitarea normal to the direction of the magnetic path. It is measured inGauss, in the cgs system of units.
Bd (Remnant Induction)-magnetic induction that remains in a magnetic material after removal of an applied magnetic force.
BHmax (Maximum Energy Product)-the point on the demagnetization curve where the values of B & H are maximized. Measured in MGOe.
Bi (Intrinsic Induction)-the contribution of themagnetic material to the total magnetic induction, B. It is the vectordifference between the magnetic induction in the material and themagnetic induction that would exist in a vacuum under the same fieldstrength, H.
This relation is expressed by: Bi=B-H
Br (Residual induction)-also the flux density, it represents the maximum flux output from the given magnetic material.
Closed Circuit-exists when the external flux path of a permanent magnet is confined with high permeability materials.
Curie Temperature (Tc)-The temperature at which themagnetic alloy completely loses it's characteristics, and the materialis no longer able to hold magnetization.
Demagnetization Curve-Also known as the BH Curve, it is the second/fourth quadrant of a hysteresis loop.
F (Magneto Motive Force)-the magnetic potential difference between any two points.
Ferromagnetic Material-material whose permeability isvery much larger than 1 (from 60 to several thousands times 1), andwhich exhibits hysteresis phenomena.
Flux-condition existing in a medium subjected to amagnetizing force. This quantity is characterized by the fact that anelectromotive force is induced in a conductor surrounding the flux atany time the flux changes in magnitude. The cgs unit of flux is theMaxwell.
Fringing Fields-leakage flux particularly associated with edge effects in a magnetic circuit.
Gauss-unit of magnetic induction (B), in the cgs unitof flux density. One gauss is equal to one maxwell per squarecentimeter, equivalent to lines per square inch, and Webers per squaremeter or Tesla.
Gauss Meter-instrument that measures the instantaneousvalue of magnetic induction, B. Its principle of operation is usuallybased on one of the following: the Hall effect, nuclear magneticresonance (NMR), or the rotating coil principle.
H (Magnetic Force)-is the magnetizing/demagnetizing force per unit length at any point in a magnetic circuit. Measured in Oersteds.
Hc (Coercive Force)-is the demagnetizing force neededto reduce residual induction, B to zero, after magnetizing tosaturation. Measured in oersteds.
Hci (Intrinsic Coercive Force)-measurement (inOersteds) of its resistance to demagnetization. It is the demagnetizingforce related in the material to zero after magnetizing to saturation.
Hysteresis Loop-is a closed curve obtained for amaterial by plotting corresponding values of magnetic induction(B), andmagnetizing force(H), for ordinates & abscissa.
Irreversible Loss-a partial demagnetization of themagnet, caused by exposure to external fields(such as high/lowtemperatures), or other factors. These losses are recoverable byremagnetization, & they can be stabilized by partial demagnetizationinduced by temperature cycles or by external magnetic fields.
Isotropic-magnetic material with magnetic propertiesthat are the same in any direction, resulting in the ability to bemagnetized in any direction.
Keeper-is a piece(s)of soft iron that is placed on orbetween the pole faces of a permanent magnet to decrease the reluctanceof the air gap and thereby reduce the flux leakage from the magnet. Theyare usually installed to resist demagnetization for Alnicomagnets/assemblies.
Knee of the Demagnetization Curve-the point at whichthe BH curve ceases to be linear. All magnet materials, even if theirsecond quadrant curves are straight line at room temperature, develop aknee at some temperature. Alnico 5 exhibits a knee at room temperature.If the operating point of a magnet falls below the knee, small changesin H produce large changes in B, and the magnet will not be able torecover its original flux output without re-magnetization.
Leakage Factor (F)-the ratio between the magnetic flux at the magnet neutral section and the average flux present in the air gap.
F=(B mA m)/(B, A g).
Leakage Flux-is the flux that is lost/leaked in the intended magnetic circuit.
Length of the Air Gap (Lg)-the length of the path of the central flux line of the air gap.
Load Line-the line drawn from the origin of thedemagnetization curve with a slope of B/H, the intersection of whichwith the B-H curve represents the operating point of the magnet. Alsosee permeance coefficient.
Magnetic Circuit-an assembly consisting of some or allof the following: permanent magnets, ferromagnetic conduction elements,air gaps, and electrical currents.
Magnetic Flux(?)-the magnetic induction(B) over an area(A), when it is uniformly distributed and is normal to the area.
Magnetic Flux, or ? = BA.
Magnetic Length, The physical length of the magnetdimension which corresponds to the direction the magnet is magnetized.This may or may not be the magnet's orientation direction.
Maxwell-the unit of magnetic flux in the cgs electromagnetic system.
North Pole-the pole of a magnet which, when freelysuspended, would point to the north magnetic pole of the earth. Thedefinition of polarity can be a confusing issue, and it is often thebest to clarify by using "north seeking pole" instead of "north pole" inspecifications.
Oersted (Oe)-the unit of magnetic force, H, in the cgselectromagnetic system. One oersted (Oe) equals a magneto motive force(F) of one gilbert per cm of flux path.
Open Circuit Condition-when a magnetized magnet is by itself with no external flux path of high permeability material.
Orientation Direction-the direction in which ananisotropic magnet should be magnetized in order to achieve optimummagnetic properties. Also known as the "axis," "easy axis," or "angle ofinclination."
Paramagnetic Material-material having a permeability slightly greater than 1.
Permeance(P)-the inverse of reluctance (R).
Permeability (µ )-term used to express vast relationships between magnetic induction (B), and the field strength (H).
Pole Pieces-ferromagnetic materials placed on magnetic poles used to shape and alter the effect of lines of flux.
Reluctance (R)-analogous to electrical resistance in acircuit. It is the quantity that determines the magnetic flux (?),resulting from a given magneto motive force (F). The relation as below:
F=magneto motive force
Return Path-conduction elements in a magnetic circuit, which provide a low reluctance path for the magnetic flux.
Reversible Temperature Coefficient-The changes in flux caused by tempersture changes that is reversible.
Saturation-The condition where the increase in themagnetic force yields no increase in induction, & all of theelementary magnetic moments are oriented in one direction.
Search Coil-a coiled conductor, usually of known areaand number of turns, that is used with a flux meter to measure thechange of flux linkage with the coil.
Sintered Magnets-this magnet is produced from acompacted powder, which is then subjected to a heat operation where thefull density and magnetic orientation is achieved.
Stabilization-is the exposure of a magnet todemagnetizing influences expected to be encountered in use in order toprevent irreversible losses during actual operation. Demagnetizinginfluences can be caused by high or low temperatures, or by externalmagnetic fields.
Temperature Coefficients-is a factor which describesthe reversible change in a magnetic property with a change intemperature. When the temperature returns to its original point, themagnetic properties return spontaneously. It usually is expressed as thepercentage change per unit of temperature.
Weber-the practical unit of magnetic flux. It is theamount of magnetic flux which, when linked at a uniform rate with asingle-turn electric current during an interval of 1 second, will inducein this circuit an electromotive of force of 1 volt.