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All About Magnetism |
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Magnetizing |
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Process of aligning the elementary magnetic areas by an external magnetic field. |
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Isotropic Magnets |
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Isotropic magnets may be magnetized in all directions with the identical magnetic features. |
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Anisotropic Magnets |
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In the production process, a preferential direction is applied to anisotropic magnets by using an external magnetic field. In a magnetizing process following later, the maximum magnetic values are obtained in this direction. |
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Hysteresis loop: |
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Describes the function between magnetic flux density B or magnetization M, and magnetic field strength H, at a magnetization cycle characterized by positive and negative extreme values. A hysteresis loop does not represent a definite functional connection between B, or M, and H, but separates into two different branches for a rising and falling magnetic field. It occurs with ferra magnets, but not with dia magnets ore paramagnets.
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Energy Product (B x H) |
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Product of flux density B and field strength H in the second quadrant of the demagnetizing- curve. The energy product has a maximum (BH)max between the points Br and BHc. The maximum energy product may be defined as maximum stored magnetic energy and serves as material constant when assessing permanent magnetic components |
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Demagnetizing Curve |
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Part of the hysterisis loop within the second quadrant of the coordinate system (B respectively M positive, H negative). By measuring the demagnetizing curve, the most important magnetic features are determined. |
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Field Strength (magnetic) H |
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Signifies value and direction of a magnetic field and may be defined in various ways. For example: The potential energy of a small permanent magnet with magnetic moment m within the magnetic field H is provided by: |
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Flux (magnetic)  |
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Product from flux density B x area F, interspersed by the magnetic field. Unit: 1 Vs = 1 Weber (Wb).
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Flux Density (magnetic) B |
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Describes the strength of the magnetic field as H does. Whereas, outside magnetizable matter, B and H differ only by a constant factor, B accounts for the influence of the magnetisation within such materials.
Unit: 1 Vs/m² = Wb/m² = 104 G = 1 T
Most common are the units
1 T = 104 G und 1 mT = 10 G |
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Gauss |
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Formerly common unit of the magnetic flux density. |
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Coercive Field Force Hc |
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There is distinction between the coercive field force BHc, the flux density, and the coercive field force IHc of the polarisation. The coercive field force BHc (in the case of the closed magnetic circle) is defined as demagnetized field strength required for the removal of the flux density B. The coercive field force IHc is the demagnetized field strength whereby the polarisation I becomes zero. Thus, by applying IHc, a body becomes non-magnetic. Practically speaking, all materials with high permeability are magnetic, mainly iron, nickel, cobalt, and their alloys.
All other materials are non-magnetic (brass, copper, wood, stone etc.). |
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Magnetic Properties of Hard Ferrite Magnet |
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Grade |
Residual |
Coercive Force |
Intrinsic Coercive Force |
Max Energy Products |
Operating |
Density |
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Flux Density Br |
Hcb |
Hcj |
(BH) max |
Temperature |
D |
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Gs (mT) |
Oe (kA/m) |
Oe (kA/m) |
MGOe (kJ/m3) |
ÆC |
g/cm3 |
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Y10T |
>=2000 (>=200) |
1600~2000 (128~160) |
2889~3391 (230-270) |
0.8~1.2 (6.4~9.6) |
<=250 |
4.5~4.9 |
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Y20 |
3200~3800 (320~380) |
1600~2400 (128~192) |
1884~3014 (150~240) |
2.3~2.7 (18.3~21.5) |
<=250 |
4.5~4.9 |
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Y25 |
3500~3900 (350~390) |
1900~2600 (152~208) |
2072~3140 (165~250) |
2.8~3.2 (22.3~25.5) |
<=250 |
4.5~4.9 |
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Y30 |
3800~4200 (380~420) |
2000~2700 (160~216) |
2072~3140 (165~250) |
3.3~3.7 (26.3~29.5) |
<=250 |
4.6~5.1 |
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Y35 |
4000~4400 (400~440) |
2200~2800 (176~224) |
2512~2889 (200~230) |
3.8~4.3 (30.3~33.4) |
<=250 |
4.7~5.1 |
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Y30BH |
3800~4000 (380~400) |
2800~3000 (224~240) |
3077~3391 (245~270) |
3.4~3.8 (27.1~30.3) |
<=250 |
4.6~5.1 |
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Magnetic characteristics of NdFeB-Magnets |
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Type |
N-27 |
N-27 H |
N-30 |
N-30 H |
N-35 |
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NdFeB |
200/64 |
200/130 |
230/95 |
230/130 |
280/95 |
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Br (mT) |
1.000-1.100 |
1020-1060 |
1080-1120 |
1080-1120 |
1170-1210 |
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BHc (kA/m) |
716 |
764 |
780 |
804 |
860 |
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BHc (KOe) |
9 |
9,6 |
9,8 |
10,1 |
10,8 |
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IHc (kA/m) |
955 |
1353 |
955 |
1353 |
955 |
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IHc (KOe) |
12 |
17 |
12 |
17 |
12 |
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BHmax (kJ/m3) |
199-223 |
199-215 |
223-239 |
223-239 |
263-279 |
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BHmax (MGOe) |
25-28 |
25-27 |
28-30 |
28-30 |
33-35 |
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Density (g/cm3) |
7,4-7,5 |
7,5-7,6 |
7,4-7,5 |
7,5-7,6 |
7,4-7,5 |
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max. Temp. (°C) |
 80
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120 |
80 |
120 |
80 |
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Type of Magnetization |
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Maxwell |
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Former unit for the magnetic flux. |
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Oersted |
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Former unit for magnetic field strength.
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Remanence Br |
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Remanence is the induction (flux density) remaining in a ferrous magnetic material after removal of the magnetizing field. The numerical value of the remanence applies as material constant for the case of the closed circle (H = 0) and is called true remanence (Br). In the opened magnetic circuit Br drops to the value of the apparent remanence Br. |
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q |
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Saturation Magnetizing |
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A magnetization, which can maximally be achieved by parallel alignment of all magnetic moments, is called saturation magnetization. |
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Sintered Magnet |
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Permanent magnet pressed from a mixture of magnetizable powders and hardened by heating in a vacuum. |
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Temperature Coefficient |
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Indicates the dependency of the magnetic material's characteristic data Br and BHc upon temperature. The temperature coefficients for Br, respectively BHc differ. |
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Tesla |
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Unit for the magnetic Flux.
1 Tesla (T)= 104 G = 1 Vs/m2 |
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Weber |
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Unit for the magnetic Flux. |
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1 weber (Wb) = 1 Vs = 108 Maxwell |
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