起始磁导率i.doc

JEA 9
术语与定义Terms & Definitions

起始磁导率μi
初始磁导率是磁性材料的磁导率（B/H）在磁化曲线始端的极限值，即
μi =×
式中
μ0为真空磁导率（）
为磁场强度的变化率（A/m）
为磁感应强度的变化率（T）
有效磁导率μe
在闭合磁路中，如果漏磁可忽略，可以用有效磁导率来表示磁芯的性能。
=
式中
L为装有磁芯的线圈的电感量（H）
N为线圈匝数
Le为有效磁路长度（m）
Ae为有效截面积 (m2)
饱和磁通密度Bs（T）
磁化到饱和状态的磁通密度。见图1。

图 1

剩余磁通密度Br（T）
从饱和状态去除磁场后，剩余的磁通密度。见图1。
矫顽力Hc（A/m）
从饱和状态去除磁场后，磁芯继续被反向磁场磁化，直至磁感应强度减为零，此时的磁场强度称为矫顽力。见图1。
损耗因子tanδ
损耗系数是磁滞损耗、涡流损耗和剩余损耗三者之和。
tanδ= tanδh + tanδe + tanδr
式中
tanδh为磁滞损耗系数
tanδe为涡流损耗系数
tanδr为剩余损耗系数
相对损耗因子 tanδ/μi
比损耗因子是损耗系数与与磁导率之比：
tanδ/μi（适用于材料）
tanδ/μe（适用于磁路中含有气隙的磁芯）
品质因数 Q
品质因数为损耗因子的倒数: Q = 1/ tanδ
温度系数αμ( 1/K)
温度系数为T1和T2范围内变化时,每变化1K相应的磁导率的相对变化量:
αμ= .
式中
μ1为温度为T1时的磁导率
μ2为温度为T2时的磁导率
相对温度系数αμr(1/K)
温度系数和磁导率之比，即
αμr = .
减落系数 DF
在恒温条件下，完全退磁的磁芯的磁导率随时间的衰减变化，即
DF = (T2>T1)
μ1为退磁后T1分钟的磁导率
μ2为退磁后T2分钟的磁导率
居里温度Tc（℃）
在该温度时材料由铁磁性（或亚铁磁）转变为顺磁性，见图2。

图2
电阻率 (Ω.m)
具有单位截面积和单位长度的磁性材料的电阻 。
密度 d (kg/m3)
单位体积材料的重量,即
d =W/V
式中
W为磁芯的重量(kg)
V为磁芯的体积(m3)
功率损耗 Pc (kW/m3)
磁芯的高磁感应强度下的单位体积损耗或单位重量损耗.该磁通密度可表示为

式中
E为施加在线圈上的电压有效值 (V)
Bm为磁感应强度的峰值 (T)
f 为频率 (Hz)
N 为线圈匝数
Ae为有效截面积(m2)
电感系数AL(nH/N2)
电感因数定义为具有一定形状和尺寸的磁芯上每一匝线圈产生的电感量,即
AL = L/N2
式中
L:为装有磁芯的线圈的电感量(H)
N:为线圈匝数

Initial permeability, μi
The initial permeability μi is the limit value at the initial magnetization curves origin point and is given by the following formula:
μi =×
Where
μ0:Permeability of vacuum（）
:Rate of change for magnetic field strength(A/m)
:Rate of change for Magnetic flux density(T)

Effective permeability, μe
This is usually defined as the permeability of a core forming a closed circuit where leakage flux is negligibly small.
=
Where
L: Self-inductance of core with coil (H)
N: Number of turns
Le: Effective magnetic path length (m)
Ae: Effective cross-sectional area (m2)

Saturation flux density, Bs (T)
The magnetic flux density at a magnetic field where his up to a approximate saturation magnetic field value.(Fig.1)

Fig.1
Remanence, Br (T)
The value of density retained by the core when the magnetic field is reduced from the saturation magnetic flux density to zero.(Fig.1)

Coactivity, Hc (A/m)
The value of magnetic field strength where by the flux density becomes zero under the intensification, in the opposite direction, of the magnetic field.(Fig.1)

Loss factor , tanδ
This is the sum of the hysteretic loss factor, eddy current loss factor and residual loss factor.
tanδ= tanδh + tanδe + tanδr
Where
tanδh is the hysterias loss factor
tanδe is the eddy current loss factor
tanδr is the residual loss factor

Relative loss factor, tanδ/μi
This is the ratio of loss factor to permeability.
tanδ/μi (for materials)
tanδ/μe (for cores with gaps in the magnetic circuit)

Quality factor, Q
This is the reciprocal of the loss factor
and is given by
Q = 1/ tanδ

Temperature coefficient, αμ (1/K)
This is the fractional difference of permeability per 1K in a temperature range of from T1 to T2.
αμ= .
Where
μ1: Permeability at temperature T1
μ2: Permeability at temperature T2

Relative temperature coefficient, αμr (1/K)
This is the temperature coefficient per unit
permeability and is given by the following equation:
αμr = .

Discommendation factor, DF
This is the factor representing the variation of permeability through time after a complete demagnetization of the core at a constant temperature.
DF = (T2>T1)
Where
μ1: Permeability T1 minutes after complete demagnetization.
μ2: Permeability T2 minutes after complete demagnetization.

Curie temperature, Tc （℃）
It is the critical temperature level at which the ferromagnetic state of the material changes to paramagnetic state.(Fig.2)

Fig.2
Electrical resistively, (Ω.m)
This is the electrical resistance per unit length and cross-sectional area of a magnetic core.

Density, d (kg/m3)
This is the weight per unit volume of a magnetic core as expressed below.
d =W/V
Where
W: Weight of magnetic body (kg)
V: Volume of magnetic body (m3)

Power loss, Pc (kW/ m 3)
Power loss denotes the loss by an electrical transformer, such as a switching power supply, under a magnetization condition featuring a high frequency and large amplitude. Operating magnetic flux density is given by the following equation.

Where
E: voltage effective value applied to coil
Bm: peak value of magnetic flux density（T）
f: Frequency (Hz)
N: Number of tunes
Ae: Effective cross-sectional arum (m2)

Inductance factor, AL (nH/N2)
This is the inductance per turn of the coil wound around the ferrite cores with definite shape and dimension.
AL = L/N2
Where
L: Inductance of the coil with ferrite core,
N: Number of tunes