Terms & Definitions

1 . Initial permeability, ui

The initial permeabilityμi is the limit value atthe initial magnetizationcurve’ S Origin point and is given by the following formula:
where
o: permeability of vacuum (4m X 1o-7 H/m)
H: Magnetic field strength (A/m)
B: Magnetic flux density (T)

2 . Effective permeability, e

This is usually defined asthe 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 ofturns
Le: effective magnetic path length (m)
Ae: effective cross-sectional area (m2)

3 . saturation magnetic flux density, Bs(T)

The magnetic flux density at a magnetic field where H is up to an approximate saturation magnetic field value. (Fig. 1)
B
Bs
Br

初始磁化曲线 Initial
m agnetization curve

Hc H
( Fig 1 )

4. Residual magnetic flux density, Br(T)

The value of flux density retained by the core when the magnetic field is reduced from the state of the effective saturation magnetic flux density to zero. (Fig. 1)

5 . Coercivity, 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)

6. Loss factor, tanδ

This is the sum of the hysteresis loss factor, eddy current loss factor and residual loss factor. tanδ=tanδh+tanδe+tanδr
where
tanδh: the hysteresis loss factor
tanδe: the eddy current loss factor
tanδr: the residual loss factor

7. ReIative Ioss factor, tanδ/μ

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

8. Quality factor, Q

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

9. Temperature coefficient, αμ(1/k)

This is the fractional difference of permeability per 1k in a temperature range of from T1 to T2.
where
μ1: permeability at temperatureT1
μ2: permeability at temperatureT2

10. ReIative temperature coefficient,αμr(1/k)

This is the temperature coefficient per unit permeability and is given by the following equation:
( T2 ＞T1 )

11. curie temperature, Tc(℃)

lt is the critical temperature level at which the ferromagnetic state of the material changes to paramagnetic state.(Fig.2)

磁导率最大值
maximum value of

磁导率最大值的80%
80% of maximum value of

居里温度（Tc）
Curie tem perature 温度 Temperature (℃ )

12. Disaccommodation factor, DF

This is the factor representing the variation of permeability through time after a complete demagnetization of the core at a constant temperature ture.
· (T2＞T1 )
where
μ1: permeability t1 minutes after complete demagnetization.
μ2: permeability t2 minutes after complete demagnetization.

13. EIectricaI resistivity,p(Ω.m)

This is the electrical resistance per unit length and cross-sectional area of a magnetic core.

14. 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)

15. Power Ioss Pc(kw/ m3、w/kg)

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(v) Bm: peak value of magnetic flux density(T) f: frequency(Hz)
N: number of coil turns
Ae: effective cross-sectional area(m2)

16. 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(H)
N: turns the coil

17. Hysteresis material constant ηB

For the hysteresis material constantηB we obtain:
ηB=tanδh/(ue.△B)
The hysteresis material constant,ηB, characterizes the material-specific hysteresis losses and is a quantity independent of the air gap in a magnetic circuit.