1、磁学量常用单位换算磁学量常用单位换算磁学量名称SI符号和单位CGS符号和单位单位换算 磁通量韦伯(Wb)麦克斯韦（Mx）1Mx=10-8Wb 磁感应强度B特斯拉(T )B高斯(Gs)1Gs=10-4T 磁场强度H安/米(A/m)H奥斯特(Oe)1Oe=103/4A/m 磁化强度M安/米(A/m)M高斯（Gs）1Gs=103A/m 磁极化强度J特斯拉(T )4M高斯（Gs）1Gs=10-4T 磁能积BH焦/米3(J/m3)BH高奥（GOe）1MGOe=102/4kJ/m3 真空磁导率410-7H/m1磁概念永磁材料：永磁材料被外加磁场磁化后磁性不消失，可对外部空间提供稳定磁场。钕铁硼永磁体常用的
2、衡量指标有以下四种：剩磁（Br）单位为特斯拉（T）和高斯（Gs）1Gs =0.0001T将一个磁体在闭路环境下被外磁场充磁到技术饱和后撤消外磁场，此时磁体表现的磁感应强度我们称之为剩磁。它表示磁体所能提供的最大的磁通值。从退磁曲线上可见，它对应于气隙为零时的情况，故在实际磁路中磁体的磁感应强度都小于剩磁。钕铁硼是现今发现的Br最高的实用永磁材料。磁感矫顽力（Hcb）单位是安/米（A/m）和奥斯特（Oe）或1 Oe79.6A/m处于技术饱和磁化后的磁体在被反向充磁时，使磁感应强度降为零所需反向磁场强度的值称之为磁感矫顽力（Hcb）。但此时磁体的磁化强度并不为零，只是所加的反向磁场与磁体的磁化强度
3、作用相互抵消。（对外磁感应强度表现为零）此时若撤消外磁场，磁体仍具有一定的磁性能。钕铁硼的矫顽力一般是11000Oe以上。内禀矫顽力（Hcj）单位是安/米（A/m）和奥斯特（Oe）1 Oe79.6A/m使磁体的磁化强度降为零所需施加的反向磁场强度，我们称之为内禀矫顽力。内禀矫顽力是衡量磁体抗退磁能力的一个物理量，如果外加的磁场等于磁体的内禀矫顽力，磁体的磁性将会基本消除。钕铁硼的Hcj会随着温度的升高而降低所以需要工作在高温环境下时应该选择高Hcj的牌号。磁能积(BH)单位为焦/米3（J/m3）或高奥（GOe）1 MGOe7. 96k J/m3退磁曲线上任何一点的B和H的乘积既BH我们称为磁能
4、积,而BH的最大值称之为最大磁能积(BH)max。磁能积是恒量磁体所储存能量大小的重要参数之一，(BH)max越大说明磁体蕴含的磁能量越大。设计磁路时要尽可能使磁体的工作点处在最大磁能积所对应的B和H附近。各向同性磁体：任何方向磁性能都相同的磁体。各向异性磁体：不同方向上磁性能会有不同；且存在一个方向，在该方向取向时所得磁性能最高的磁体。烧结钕铁硼永磁体是各向异性磁体。取向方向：各向异性的磁体能获得最佳磁性能的方向称为磁体的取向方向。也称作“取向轴”，“易磁化轴”。磁场强度：指空间某处磁场的大小，用H表示，它的单位是安/米（A/m）。磁化强度：指材料内部单位体积的磁矩矢量和，用M表示，单位是安
5、/米（A/m）。磁感应强度：磁感应强度B的定义是：B=0(H+M)，其中H和M分别是磁化强度和磁场强度，而0是真空导磁率。磁感应强度又称为磁通密度，即单位面积内的磁通量。单位是特斯拉（T）。磁通：给定面积内的总磁感应强度。当磁感应强度B均匀分布于磁体表面A时，磁通的一般算式为 =BA。磁通的SI单位是麦克斯韦。相对磁导率：媒介磁导率相对于真空磁导率的比值，即r= /o。在CGS单位制中，o=1。另外，空气的相对磁导率在实际使用中往往值取为1，另外铜、铝和不锈钢材料的相对磁导率也近似为1。磁导：磁通与磁动势F的比值，类似于电路中的电导。是反映材料导磁能力的一个物理量。磁导系数Pc：又为退磁系数，
6、在退磁曲线上，磁感应强度Bd与磁场强度Hd的比率，即Pc =Bd/Hd，磁导系数可用来估计各种条件下的磁通值。对于孤立磁体Pc只与磁体的尺寸有关，退磁曲线和Pc线的交点就是磁体的工作点，Pc越大磁体工作点越高，越不容易被退磁。一般情况下对于一个孤立磁体取向长度相对越大Pc越大。因此Pc是永磁磁路设计中的一个重要的物理量。Glossary of Magnet TerminologyAir Gap -The external distance from one pole of the magnet to the other though a non-magnetic material (usual
7、ly air).Anisotropic -An anisotropic material has different properties in different directions. For example, wood which has a grain is stronger in some one direction than another. Like wood, neodymium magnets are also anisotropic. Even before it is magnetized, a neodymium magnet has a preferred magne
8、tization direction. See our articleAll About Magnetization Directionfor more info.Neodymium magnets are made with a preferred magnetization direction which can not be changed. These materials are either manufactured in the influence of strong magnetic fields or pressed a specific way, and can only b
9、e magnetized through the preferred axis.Sintered Neodymium (Iron Boron) and Samarium Cobalt magnets are anisotropic.B/H Curve -The result of plotting the value of the magnetic field (H) that is applied against the resultant flux density (B) achieved. This curve describes the qualities of any magneti
10、c material. A graphic explanation can be foundhere.BHmax(Maximum Energy Product)-The Maximum Energy Product at the point on the B/H Curve that has the most strength, expressed in MGOe (MegaGaussOersteds). When describing the grade of a neodymium magnet, this number is commonly referred to as the N n
11、umber, as in Grade N52 magnets.In the picture at right, it is the area inside the box, under the curve.Brmax(Residual Induction)-Also called Residual Flux Density. The magnetic induction remaining in a saturated magnetic material after the magnetizing field has been removed. This is the point at whi
12、ch the hysteresis loop crosses the B axis at zero magnetizing force, and represents the maximum flux 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.C.G.S. Abbreviation for the Centimeter, Gram
13、s, Second system of measurement.Coercive Force (Hc) -The demagnetizing force, measured in Oersteds, necessary to reduce observed induction, B, to zero after the magnet has previously been brought to saturation.Curie Temperature (Tc)-The temperature at which a magnet loses all of its magnetic propert
14、ies.Demagnetization Curve -The second quadrant of the hysteresis loop, generally describing the behavior of magnetic characteristics in actual use. Also known as the B-H Curve. Find these curves for some of our most popular magnet grades on ourBH Curvespage.Demagnetization Force -A magnetizing force
15、, typically in the direction opposite to the force used to magnetize it in the first place. Shock, vibration and temperature can also be demagnetizing forces.Dimensions-The physical size of a magnet including any plating or coating.Dimensional Tolerance-An allowance, given as a permissible range, in
16、 the nominal dimensions of a finished magnet. The purpose of a tolerance is to specify the allowed leeway for variations in manufacturing.(Magnetic) Dipole Moment (m)-a quantity that describes the torque a given magnet will experience in an external magnetic field.Some folks (like physicists) use a
17、magnetic dipole model to simulate or mathematically model a magnet or group of magnets. Mathematically, its easier than considering the complexities of weird magnet shapes. Its not theoretically perfect. Using it wont always match measured field strengths near a neodymium magnet. It works great for
18、a sphere, but isnt correct near other shapes like discs or blocks. Its a great approximation when youre measuring far away from a magnet, but not so good close up, especially near the edges of a magnet.Calculate the dipole moment using the formulam = dipole moment in A m2= Br x V / o, where:Bris Br
19、max, the Residual Flux Density, expressed in Tesla.Vis the volume of the magnet, expressed in cubic meters.ois the permeability of a vacuum, or 4 x 10-7N/A2.Electromagnet -A magnet consisting of a solenoid with an iron core, which has a magnetic field only during the time of current flow through the
20、 solenoid. Learn more in ourElectromagnetsarticle.Ferromagnetic Material -A material that either is a source of magnetic flux or a conductor of magnetic flux. Most ferromagnetic materials have some component of iron, nickel, or cobalt.Gauss- Unit of magnetic induction, B. Lines of magnetic flux per
21、square centimeter in the C.G.S. system of measurement. Equivalent to lines per square inch in the English system, and webers per square meter or tesla in the S.I. system. 10,000 gauss equals 1 tesla.Gauss meter -An instrument used to measure the instantaneous value of magnetic induction, B, usually
22、measured in Gauss (C.G.S.). Also called a DC magnetometer.Gilbert -The unit of magnetomotive force, F, in the C.G.S. system.Hysteresis Loop -A plot of magnetizing force versus resultant magnetization (also called a B/H curve) of the material as it is successively magnetized to saturation, demagnetiz
23、ed, magnetized in the opposite direction and finally remagnetized. With continued recycles, this plot will be a closed loop which completely describes the characteristics of the magnetic material. The size and shape of this loop is important for both hard and soft materials.With soft materials, whic
24、h are generally used in alternating circuits, the area inside this loop should be as thin as possible (it is a measure of energy loss). But with hard materials the fatter the loop, the stronger the magnet will be.The first quadrant of the loop (that is +X and +Y) is called the magnetization curve. I
25、t is of interest because it shows how much magnetizing force must be applied to saturate a magnet. The second quadrant (-X and +Y) is called the Demagnetization Curve.A graphic explanation can be foundhere.Induction, (B) -The magnetic flux per unit area of a section normal to the direction of flux.
26、Measured in Gauss, in the C.G.S. system of units.Intrinsic Coercive Force (Hci) -Indicates a materials resistance to demagnetization. It is equal to the demagnetizing force which reduces the intrinsic induction, Bi, in the material to zero after magnetizing to saturation; measured in oersteds.Irreve
27、rsible Losses -Partial demagnetization of the magnet, caused by exposure to high or low temperatures, external fields, shock, vibration, or other factors. These losses are only recoverable by remagnetization. Magnets can be stabilized against irreversible losses by partial demagnetization induced by
28、 temperature cycles or by external magnetic fields.Isotropic Material -A material that can be magnetized along any axis or direction (a magnetically unoriented material). The opposite of Anisotropic Magnet.Keeper -A soft iron piece temporarily added between the poles of a magnetic circuit to protect
29、 it from demagnetizing influences. Also called a shunt. Keepers are generally not needed for Neodymium and other modern magnets. They are more commonly used with older AlnicoHorseshoe Magnets.Kilogauss -One Kilogauss = 1,000 Gauss = Maxwells per square centimeter.Magnet -A magnet is an object made o
30、f certain materials which create a magnetic field. Every magnet has at least one north pole and one south pole. By convention, we say that the magnetic field lines leave the North end of a magnet and enter the South end of a magnet. This is an example of a magnetic dipole (di means two, thus two pol
31、es).If you take a bar magnet and break it into two pieces, each piece will again have a North pole and a South pole. If you take one of those pieces and break it into two, each of the smaller pieces will have a North pole and a South pole. No matter how small the pieces of the magnet become, each pi
32、ece will have a North pole and a South pole. It has not been shown to be possible to end up with a single North pole or a single South pole which is a monopole (mono means one or single, thus one pole).Magnetic Circuit -Consists of all elements, including air gaps and non-magnetic materials that the magnetic flux
