Magnetization Process
Yüklə 260,48 Kb. Pdf görüntüsü
|
- Bu səhifədəki naviqasiya:
- China Germany Japan Others UK TOTAL MAGNET WEIGHT IMPORTED INTO THE US
- Definitions of Terminology in Magnetics
- Bd/Hd Slope of the operating line
- (BH)max Maximum energy product
- Bi (or J) Intrinsic induction
Global Trend for Magnets 0 5000000 10000000 15000000
20000000 25000000
30000000 35000000
1992 1993
1994 1995
1996 1997
1998 1999
2000 2001
2002 2003
2004 2005
China Germany Japan Others UK TOTAL MAGNET WEIGHT IMPORTED INTO THE US 0 20,000,000 40,000,000 60,000,000 80,000,000 100,000,000 120,000,000 1992
1993 1994
1995 1996
1997 1998
1999 2000
2001 2002
2003 2004
2005 TOTAL MAGNETS VALUE IMPORTED INTO THE US China Germany
Japan Other
United Kingdom 4
Magnetic Materials Introduction
Ferrites Commonly known as Ceramics, have been in production since the 1950's. They are primarily made from Iron Oxide (FeO) and the addition of Sr and Ba through a calcining process. They are the least expensive and most common of all magnet materials. Primary grades are C1, C5 and C8. They are mostly used in motors and sensors.
Alnico These are one of the oldest commercially available magnets and have been developed from earlier versions of magnetic steels. Primary composition is Al, Ni and Co, hence the name. Although they have a high remanent induction, they have relatively low magnetic values because of their easy of demagnetization. However, they are resistant to heat and have good mechanical features. Common applications are in measuring instruments and high temperature processes such as holding devices in heat treat furnaces.
Co elements in their composition. Magnetic properties are high and they have very good temperature characteristics. They are also more expensive than the other magnet materials. They come mostly in two grades: SmCo 5 and Sm
2 Co 17 , also known as SmCo 1:5 and 2:17. Common uses are in aerospace, military and medical industries.
Neodymium Also known as Neo, these are the strongest and most controversial magnets. They are in the rare earth family because of the Nd, B, Dy, Ga elements in their composition. A relatively new group of commercial magnets, they are controversial because they are the only magnets that have been patented for both composition and processing. The patent and licensing issues are important and will be discussed later in this guide.
either extrusion, compression, calendaring or injection molding processes. The magnetic properties are lower because they sometimes lose their anisotropy and they are not fully dense due to the introduction of resins and epoxies. The main advantage to this group is that they can be made in complex shapes and can be insert, over-molded and co-molded with other materials.
Definitions of Terminology in Magnetics
Ag Area of the air gap , or the cross sectional area of the air gap perpendicular to the flux path, is the average cross sectional area of that portion of the air gap within which the application interaction occurs, Area is measured in sq. cm. in a plane normal to the central flux line of the air gap.
, is the cross sectional area of the magnet perpendicular to the central flux line, measured in sq. cm. at any point along its length. In design, Am is usually considered the area at the neutral section of the magnet.
, is the magnetic field induced by a field strength, H, at a given point. It is the vector sum, at each point within the substance, of the magnetic field strength and resultant intrinsic induction. Magnetic induction is the flux per unit area normal to the direction of the magnetic path.
, is any magnetic induction that remains in a magnetic material after removal of an applied saturating magnetic field, Hs. (Bd is the magnetic induction at any point on the demagnetization curve; measured in gauss.)
, is the ratio of the remanent induction, Bd, to a demagnetizing force, Hd. It is also referred to as the permeance coefficient, shear line, load line and unit permeance.
, indicates the energy that a magnetic material can supply to an external magnetic circuit when operating at any point on its demagnetization curve; measured in megagauss-oersteds.
, is the maximum product of (BdHd) which can be obtained on the demagnetization curve.
, is the maximum intrinsic induction possible in a material.
, is the average value of magnetic induction over the area of the air gap, Ag; or it is the magnetic induction measured at a specific point within the air gap; measured in gauss.
, is the contribution of the magnetic material to the total magnetic induction, B. It is the vector difference between the magnetic induction in the material and the magnetic induction that would exist in a vacuum under the same field strength, H. This relation is expressed by the equation:
Bi = B - H Bi = intrinsic induction in gauss B = magnetic induction in gauss H = field strength in oersteds.
6
Yüklə 260,48 Kb. Dostları ilə paylaş:
|