02 Technical

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Inductance of Wound Cores

The inductance of a core and the number of turns can be calculated by using the following formula.

Magnetic Design Formula

L = Where L = induntance (H) = core permeability N = number of turns A = core cross section area (cm2) l = mean magnetic path length (cm) LN = inductance for N turns (H) AL = nominal inductance(nH/N2)

Where H = magnetizing force (Oersteds) N = number of turns I = peak magnetizing current (A) = mean magnetic path length (cm) Bmax = maximum flux density (Gauss) Erms = voltage across coil (V) A = core cross section area (cm2) f = frequency (Hz) = material permeability

N = 10 turns (our standard wound turns for M040-066A) A = 0.100cm2 (please see the page 56) = 2.380cm (please see the page 56) LN = 66 x 10

2 x 10-3 = 6.60(H)

0.4N2A x 10-2

Required N =

0.4NI

LN = AL x N2

103

L1

Example) M040066A

L = = 6.60(H)0.4 x 125 x 102 x 0.100 x 10-2

2.380

The relations of Permeability-Flux Density(B)-Magnetizing Force(H)

H = (Amperes Law)

(Faradays Law)Ermsx102

4.44fANBmax =

BH

=

2

L2

2=

Amperes Law : The law is the magnetic equivalent of Gausss law. It relates the circulating magnetic field in a closed loop to the electric current passing through the loop

Faradays Law : The law that defines the relationship of the voltage induced across the winding of a core to the flux density within the core

( )1/2desired L(nH)

AL(nH / N2)N1 N2

10 11

www.dongbucni.co.kr

Technical Information

Core : M040066AApplied current : 3A

The total core losses are made up of three maincomponents : Hysteresis, eddy current and residual losses.

1) Inductance Calculation at 0A

Inductance calculation by Permeability vs. DC bias curves Specification

L = = 6.60(H)

N = 10 turns (our standard wound turns for M040-066A) A = 0.100cm2 (please see the page 56) = 2.380cm (please see the page 56) LN = 66 x 10

2 x 10-3 = 6.60(H)

Where Rac = effective resistance (Ohm) a = hysteresis loss coefficient c = residual loss coefficient e = eddy current loss coefficient = same as before mentioned L = inductance Bmax = maximum flux density f = frequency

Eddy current loss

Residual loss

Hysteresis loss

Total loss factor

0.4 x 125 x 102 x 0.100 x 10-22.380

RacL

2) Magnetizing force (H : Oe) is calculated by Ampere law to achieve the roll off

H = = = 15.8(Oe)0.4 x x N x I

0.4 x x 10 x 3

2.38

3) When the magnetizing force(H) is 15.8 Oe, yielding 85% of initial permeability. Therefore, the Inductance at 3A is

L(3A) = 6.6 x 0.85 = 5.6(H)

Core loss

= aBmaxf + cf + ef2

10 11

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Window Area = x

The Q factor is the ratio of reactance to the effective resistance and is often used as measure of performance. So, the Q factor represents the effect of electrical resistance.

Q Factor

Q =

Where Q = quality factor = 2f (Hz) L = inductance (H) Rdc = DC winding resistance (Ohm) Rac = resistance due to core losses (Ohm) Rd = resistance due to winding dielectric

losses (Ohm)

Le = effective mean magnetic path length (cm) Ae = effective core cross section area (cm2 ) Ve = effective core volume (cm3) OD = core outer diameter before coating (cm) ID = core inner diameter before coating (cm) HT = core height before coating (cm)

LRdc + Rac + Rd =

ReactanceTotal Resistance

x HT

Le = (OD-ID)

Physical constant of core

In ODID

Ve = Le x Ae

CGS (unit) By To obtain (unit) Factor

Magnetic Flux Density (B) Gauss (G) 10-4 Tesla (T) 1T=104G

Magnetizing Force (H) Oersted (Oe) 79.58 Amperes per Meter (A/m) 1A/m=4/103Oe

Conversion Table

ID2( )

2

Ae = OD-ID

2

12 13

www.dongbucni.co.kr


The increase in surface temperature of a component in free-standing air due to the total power dissipation (both copper and core loss). The following formula has been used to approximate temperature rise:

Total Power Loss = Copper Loss + Core LossSurface Area means in case of wound core

Nominal DC Resistance, in ohm/mH, at any given winding factor can be calculated by using the following equations:

Temperature Rising Calculation

Temperature Rise(oC) =

Where /mhwf = mh for chosen winding factor /mhu = unity value, listed for each core size wf = chosen winding factor Kwf = length/turn for chosen wf* Ku = length/turn for unity(100%) wf*

* see Winding Turn Length on core size pages

Total Power Loss (milliwatts)Surface Area(cm2)

/mhuwf

KwfKu

Nominal DC Resistance

/mhwf = x

The value of Rdc for any given winding factor can be computed as follows:

Where Rdcwf = Rdc for chosen winding factor Rdcu = unity value, listed for each core size(ohms) wf = chosen winding factor Kwf = length/turn for chosen wf* Ku = length/turn for unity(100%) wf* * see Winding Turn Length on core size pages

KwfKu

Rdcwf = Rdcu x wfx

( )0.833

12 13

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

MPP

10

High Flux

100 1000 10000

Frequency (kHz)

Frequency (kHz)

Per

cent

Per

mea

bilit

y(%

)P

erce

nt P

erm

eabi

lity(

%)

10 100 1000 10000

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

14 26 60

125

14

26

60

125

Permeability vs. Frequency

14 15

www.dongbucni.co.kr


Permeability vs. Frequency

Sendust100

98

96

94

92

90

88

86

84

82

80

100

90

80

70

60

50

40

30

20

10

0

Frequency (kHz)

Per

cent

Per

mea

bilit

y(%

)P

erce

nt P

erm

eabi

lity(

%)

Power Flux

60

90

14 26

35 60

75

125

90

Frequency (kHz)

10 100 1000 10000

10 100 1000 10000

14 15

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

MPP

Normal Magnetizing Curves

8000

7000

6000

5000

4000

3000

2000

1000

0

High Flux

Flux

Den

sity

(Gau

ss)

1 10 100 1000

14000

13000

12000

11000

10000

9000

8000

7000

6000

5000

4000

3000

2000

1000

0

125

60

125

60

26

26

Flux

Den

sity

(Gau

ss)

1 10 100 1000

Magnetizing Force (Oersteds)


16 17

www.dongbucni.co.kr


Sendust

16000

14000

12000

10000

8000

6000

4000

2000

01 10 100 1000



11000

10000

9000

8000

7000

6000

5000

4000

3000

2000

1000

0

90

60

Flux

Den

sity

(Gau

ss)

Flux

Den

sity

(Gau

ss)

Power Flux

1 10 100 1000

125

90

75

60

26

Normal Magnetizing Curves

16 17

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

MPP4

3

2

1

0

-110 100 1000 10000

10 100 1000 10000

AC Flux Density (Gauss)

Per

cent

Cha

nge

of P

erm

eabi

lity

(%)

125

60

26

High Flux30

25

20

15

10

5

0

-5

-10


Per

cent

Cha

nge

of P

erm

eabi

lity

(%) 125

60

26

Permeability vs. AC Flux Density

18 19

www.dongbucni.co.kr

Permeability vs. AC Flux Density

4

3

2

1

0

-1

4

3

2

1

0

-1


Per

cent

Cha

nge

of P

erm

eabi

lity

(%)

perc

ent c

hang

e of

per

mea

bilit

y(%

)

Sendust

Power Flux


125

90

75

60

26

60


10 100 1000 10000

10 100 1000 10000

18 19

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

MPP100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

DC Mangnetizing Force (Oe)


Per

cent

Per

m e

abili

ty (%

)P

erce

nt P

erm

eab

ility

(%)

High Flux

125 60 26 14

125 60 26 14

1 10 100 1000

1 10 100 1000

20 21

Permeability vs. DC Bias Curves

www.dongbucni.co.kr


Sendust100

90

80

70

60

50

40

30

20

10

01 10 100 1000

1 10 100 1000

100

90

80

70

60

50

40

30

20

10

0



Per

cent

Per

m e

abili

ty (%

)P

erce

nt P

erm

eab

ility

(%)

Power Flux

Technical Information125 90 7560 35 26 14

90 60

Permeability vs. DC Bias Curves

20 21

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Factors of Permeability vs. DC Bias Fit Formula

14 -3.5204E-05 -1.8222E-08 -3.5714E-05 5.1020E-08

26 -4.7041E-05 -2.2758E-09 -4.6154E-05 2.9586E-08

60 -8.2917E-05 1.8519E-09 -5.8333E-05 2.7778E-08

125 -7.2890E-05 1.3824E-09 -9.0400E-05 3.2000E-08

0 a b c d

14 -7.6531E-06 -3.2799E-09 1.4286E-06 5.1020E-09

26 -2.4556E-05 -1.7069E-09 1.1538E-05 5.9172E-09

60 -2.8972E-05 -4.6296E-10 -2.5000E-05 8.3333E-09

125 -3.4861E-05 3.0720E-10 -3.5200E-05 6.4000E-09

MPP

High Flux

a1

=c d + +

b+ + 20 30 20

2 0

40

2

e ff

0 a b c d

22 23

www.dongbucni.co.kr

a1

=c d + +

b+ + 20 30 20

2 0

40

2

e ff

Factors of Permeability vs. DC Bias Fit Formula

14 -3.6735E-05 -7.2886E-09 -2.1429E-05 3.0612E-08

26 -9.1716E-05 2.2758E-09 8.4615E-05 1.4793E-08

35 -1.0522E-04 2.3324E-09 4.8571E-05 1.6327E-08

60 -7.4250E-05 1.8519E-09 1.3333E-05 1.3889E-08

75 -9.1058E-05 2.1333E-09 3.4667E-05 1.0667E-08

90 -8.2457E-05 1.7833E-09 1.0000E-05 2.4691E-08

125 -9.1155E-05 1.9456E-09 -9.6000E-06 2.5600E-08

60 -3.5444E-05 -1.8519E-10 6.6667E-07 8.3333E-09

90 -5.4914E-05 8.2305E-10 -4.4444E-06 8.6420E-09

Sendust

Power Flux


0 a b c d

0 a b c d

22 23

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Factors of Percentage Permeability (x100) calculation

14 -4.9286E-04 -3.5714E-06 -5.0000E-04 1.0000E-05

26 -1.2231E-03 -1.5385E-06 -1.2000E-03 2.0000E-05

60 -4.9750E-03 6.6667E-06 -3.5000E-03 1.0000E-04

125 -9.1112E-03 2.1600E-05 -1.1300E-02 5.0000E-04

0 k l m n

14 -1.0714E-04 -6.4286E-07 2.0000E-05 1.0000E-06

26 -6.3846E-04 -1.1538E-06 3.0000E-04 4.0000E-06

60 -1.7383E-03 -1.6667E-06 -1.5000E-03 3.0000E-05

125 -4.3576E-03 4.8000E-06 -4.4000E-03 1.0000E-04

MPP

High Flux

k l1Ratio

of Perm . =

+ + 2

m n1 + + 2

0 k l m n

24 25

www.dongbucni.co.kr

k l1Ratio

of Perm . =

+ + 2

m n1 + + 2

Factors of Percentage Permeability (x100) calculation

14 -5.1429E+00 -1.4286E-02 -3.0000E-04 6.0000E-06

26 -2.3846E+01 1.5385E-02 2.2000E-03 1.0000E-05

35 -3.6829E+01 2.8571E-02 1.7000E-03 2.0000E-05

60 -4.4550E+01 6.6667E-02 8.0000E-04 5.0000E-05

75 -6.8293E+01 1.2000E-01 2.6000E-03 6.0000E-05

90 -7.4211E+01 1.4444E-01 9.0000E-04 2.0000E-04

125 -1.1394E+02 3.0400E-01 -1.2000E-03 4.0000E-04

60 -2.1267E-03 -6.6667E-07 4.0000E-05 3.0000E-05

90 -4.9422E-03 6.6667E-06 -4.0000E-04 7.0000E-05

Sendust

Power Flux


0 k l m n

0 k l m n

24 25

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Typical Core Loss of MPP

MPP 14

Flux Density (Gauss)

PL=2.33F1.31B2.19

10 100 1000 10000

MPP 26

200KH

z100

KHz

50KHz 25K

Hz

Cor

e Lo

ss (m

W/c

m3 )


10 100 1000 10000

200KH

z100

KHz

50KHz 25K

Hz

Cor

e Lo

ss (m

W/c

m3 )

10000

1000

100

10

1

0.1

10000

1000

100

10

1

0.1

PL=C X F

a X B

b

(F : kHz - B : kG)

Perm. C a b

14 2.33 1.31 2.19

26 1.39 1.28 1.29

PL=1.39F1.28B1.29

26 27

www.dongbucni.co.kr


10 100 1000 10000

MPP 60

MPP 125

PL=0.64F1.41B2.20

200KH

z100

KHz 50K

Hz 25KH

z


10000

1000

100

10

1

0.110 100 1000 10000

200KH

z100

KHz

50KHz

25KHz

Cor

e Lo

ss (m

W/c

m3 )

10000

1000

100

10

1

0.1

Cor

e Lo

ss (m

W/c

m3 )

Typical Core Loss of MPP

PL=C X F

a X B

b

(F : kHz - B : kG)

Perm. C a b

60 0.64 1.41 2.20

125 1.02 1.40 2.03

PL=1.02F1.40B2.03


26 27

Typical Core Loss 01 High Flux

Hlgh Flux 14 p. HIDl

/ '2.~ g OiJ' ~

1"

100

'"

({

E)

e

P l =726fO.95Bul

1III HlXl

Flux Density (Ga=) 100

0.1

'"

H lgh Flux 26 (JlXJ

/ l &

1m

100

10

(E

E) $

g

PL =1 .38F\37B230

1 lXl 1(lXJ

FI, Oensily (Gauss)

100 0.1

10

b a c Po

www.dongbucni.co.kr

Typical Core Loss of High Flux

PL=C X F

a X B

b

(F : kHz - B : kG)


10 100 1000 10000

HIgh Flux 60

HIgh Flux 125

200KH

z 100KH

z 50KHz 25K

Hz


10 100 1000 10000

200KH

z 100KH

z50K

Hz25K

Hz

10000

1000

100

10

1

0.1

Cor

e Lo

ss (m

W/c

m3 )

10000

1000

100

10

1

0.1

Cor

e Lo

ss (m

W/c

m3 )

PL=3.65F1.15B2.16

PL=1.62F1.32B2.20


Perm. C a b

60 3.65 1.15 2.16

125 1.62 1.32 2.20

28 29

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Typical Core Loss of Sendust

Sendust 14, 26


200KHz 100

KHz 50KHz

25KHz

Cor

e Lo

ss (m

W/c

m3 )

PL=2.27F1.26B2.08

10 100 1000 10000

10000

1000

100

10

1

0.1


10 100 1000 10000

Sendust 60,75,90,125

200KH

z 100KHz 50K

Hz 25KHz

10000

1000

100

10

1

0.1

Cor

e Lo

ss (m

W/c

m3 )

PL=2.00F1.31B2.15

PL=C X F

a X B

b

(F : kHz - B : kG)

Perm. C a b

14, 26 2.27 1.26 2.08

60,75,90,125 2.00 1.31 2.15

30 31

www.dongbucni.co.kr

Power Flux 60, 90


10000

1000

100

10

1

0.110 100 1000 10000

200KH

z100

KHz 50K

Hz 25KHz

Cor

e Lo

ss (m

W/c

m3 )

PL=4.51F1.25B2.21

Typical Core Loss of Power Flux

Perm. C a b

60, 90 4.51 1.25 2.21


PL=C X F

a X B

b

(F : kHz - B : kG)

30 31

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Temperature Stability

MPP

3.0

2.0

1.0

0.0

-1.0

-2.0-30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130

Temperature (oC)

Per

cent

Per

mea

bilit

y (%

) 125 60

26

14

5.0

4.0

3.0

2.0

1.0

0.0

-0.1

-0.2

-0.3

-0.4

-0.5

Per

cent

Per

mea

bilit

y (%

)

60 2614

125

High Flux

-30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130

Temperature (oC)

32 33

www.dongbucni.co.kr

Per

cent

Per

mea

bilit

y (%

)

Temperature Stability

Sendust

125

90

75

90

60

Per

cent

Per

mea

bilit

y (%

)

14,2660

2.0

1.0

0.0

-1.0

-2.0

-3.0

-4.0

-5.0

-6.0

-7.0

5.0

4.0

3.0

2.0

1.0

0.0

-0.1

-0.2

-0.3

-0.4

-0.5

Power Flux

-30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130

Temperature (oC)

-30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130

Temperature (oC)


32 33

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Symbol and Units

Symbol Discription Unit

Ae effective cross section area of a core cm2

AL apparent inductance nH/N2

B magnetic flux density T

Br remanence flux density T

Bmax maximum flux density T

Erms sinusoidal rms voltage across winding V

H magnetizing force A/m

Hc coercive force A/m

Hmax maximum magnetizing force A/m

e effective magnetic path length cm

L inductance H

N number of turns -

PL core loss of a core mW/cm3

Q quality factor -

V volume of a core cm3

Rdc DC winding resistance

absolute permeability -

e effective permeability -

i initial permeability -

r relative permeability -

34 35

www.dongbucni.co.kr

Glossary of Terms

AC flux density

Number of flux lines per unit of cross-sectional area generated by an alternating magnetic field; Gauss

Air Gap

A non-magnetic discontinuity in a ferro-magnetic circuit. For example, the space between the poles of a magnet, although filled with brass of wood and other non-magnetic material, is nevertheless called an air gap.

Breakdown Voltage

(1)The voltage at which an insulator or dielectric ruptures, or at which ionization and conduction take place in a gas or vapor. (2) The reverse voltage at w h i c h a v a l a n c h e b r e a k d o w n o c c u r s i n a semiconductor. (3) Maximum AC or DC voltage that can be applied from the input to output (or chassis) of a converter without causing damage.

Choke

An inductor which is intended to filter, or 'choke', out unwanted signals.

Copper Loss

The power loss by current flowing through the winding. The power loss is equal to the square of the current multiplied by the resistance of the wire (I2 X R). This power loss is transferred into heat.

Core Losses

Core losses are caused by an altering magnetic field in the core material. The losses are a function of the operating frequency and the total magnetic flux swing. The total core losses are made up of three main components: Hysteresis, eddy current and residual losses. These losses vary considerably from one magnetic material to another. Applications such as higher power and higher frequency switching regulators require careful core selection to yield the highest inductor performance by keeping the core losses to a minimum.

Core Saturation

The DC bias current flowing through an inductor which causes the inductance to drop by a specified amount from the initial zero DC bias inductance va lue . Common spec i f i ed induc tance d rop percentages include 10% for ferrite cores and 20% for iron powder cores in energy storage applications. Also referred to as saturation current.

Curie Temperature

The temperature at which a magnetic material loses its magnetic properties. The core's permeability typical ly increases dramat ical ly as the core temperature approaches the curie temperature, which causes the inductance to increase. The permeabi l i ty drops to near unity at the curie temperature, which causes the inductance to drop dramatically. The curie point is the temperature at which the initial permeability (i) has dropped to 10% of its value at room temperature.


34 35

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Glossary of Terms

DC Bias

Direct current (DC) applied to the winding of a core in addition to any time-varying current. Inductance with DC bias is a common specification for powder cores. The inductance will 'roll off' gradually and predictably with increasing DC bias.

DCR

Direct Current Resistance - The resistance of the inductor winding measured with no alternating current. The DCR is most often minimized in the design of an inductor. The unit of measure is ohms and it is usually specified as a maximum rating.

Distributed Capacitance

(1) In the construction of an inductor, each turn of wire or conductor acts as a capacitor plate. The combined effects of each turn can be presented as a single capaci tance known as the distr ibuted capacitance. The capacitance is in parallel with the inductor. This parallel combination will resonate at some frequency, which is called the self-resonant frequency (SRF). Lower distributed capacitance for a given inductance will result in a higher SRF and vice versa. (2) Capacitance that is not concentrated within a lumped capacitor, but spread over a circuit or group of components.

Eddy Current Losses

Core losses associated with the electrical resistivity of the magnetic material and induced voltages within the material. Eddy currents are inversely proportional to material resistivity and proportional to the rate of

change of flux density. Eddy current losses are present in both the magnetic core and windings of an inductor. Eddy currents in the winding, or conductor, contribute to two main types of losses: losses due to proximity effects and skin effects. As for the core losses, an electric field around the flux lines in the magnetic field is generated by alternating magnetic flux. This will result in eddy currents if the magnetic core material has electrical conductivity. Losses result from this phenomenon since the eddy currents flow in a plane that is perpendicular to the magnetic flux lines. Eddy current and hysteresis losses are the two major core loss factors. Eddy current loss becomes dominant in powder cores as the frequency increases.

Effective Permeability

For a magnetic circuit constructed with an air gap, or g a p s , t h e p e r m e a b i l i t y o f a h y p o t h e t i c a l homogeneous material that would provide the same reluctance, or net permeability.

EMC

Electromagnetic compatibility. The ability of an e lect ronic dev ice to operate in i ts in tended environment without its performance being affected by EMI and without generating EMI that will affect other equipment.

EMI

Electro-Magnetic Interference - An unwanted electrical energy in any form. EMI is often used interchangeably with 'noise' and 'interference'.

36 37

www.dongbucni.co.kr

Glossary of Terms

Flux Density (B)

The corresponding parameter for the induced magnetic field in an area perpendicular to the flux path. Flux density is determined by the field strength and permeabil i ty of the medium in which it is measured.

Full Winding

A winding for toroidal cores that will result in 45% of the core's inside diameter remaining.

Harmonics

Energy at integral multiples of the frequency of the fundamental signal. Normally expressed as THD (Total Harmonic Distortion) but can be specified for harmonics of interest in either a percentage of or decibels below the power level of the fundamental frequency signal.

Hysteresis Loss

Hysteresis means to lag behind. This is the tendency of a magnetic material to retain its magnetization. Hysteresis causes the graph of magnetic flux density versus magnetizing force (B-H curve) to form a loop rather than a line. The area of the loop represents the difference between energy stored and energy released per unit of volume of material per cycle. This difference is called the hysteresis loss.

Hysteresis Loop

A closed curve obtained for a material by plotting

corresponding values of flux density for the ordinate and magnetizing force for the abscissa when the material is passing through a complete cycle between definite limits of either magnetizing force or f lux density. I f the material is not driven into saturation it is said to be on a minor loop.

High Q filters

A filter circuit (inductor and/or capacitor) that exhibits high Q. It is very frequency-sensitive and filters out or allows to pass, only those frequencies within a narrow band.

Magnetizing ForceCoercive

Force

Remanence

Flux Density

MaximumFlux DensityMaximum

Permeability

IntialPermeability


36 37

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Glossary of Terms

Impedance

The total opposition offered by a component or circuit to the flow of alternating or varying current at a particular frequency, including both the AC and DC component.. Impedance is expressed in ohms and is similar to the actual resistance in a direct current circuit. In computations, impedance is handled as a complex ratio of voltage to current. The ohm is the un i t o f impedance . Impedance i s t yp i ca l l y abbreviated as "z" or "Z". The frequency-invariant, real component of impedance is resistance. The f requency-var iant , imaginary component o f impedance is reac tance. The rec ip roca l o f impedance is admittance.

Inductance Factor (AL)

The inductance rating of a core in nanoHenries per turn squared (nH/N2) based on a peak flux density of 10 gauss (1 mT) at a frequency of 10 kHz. An AL value of 40 would produce 400H of inductance for 100 turns and 40mH for 1000 turns.

Initial Permeability

That value of permeability at a peak AC flux density of 10 gauss (1 mT).

Magnetic Energy

The product of the flux density (B) and the (de)magnetizing force (H) in a magnetic circuit required to reach that flux density.

Magnetostriction

The expansion and contraction of a magnetic

material with changing magnetic flux density. The saturation magnetostriction coefficient has the symbols. It is change of length divided by original length (a dimensionless number) and is measured at the saturation flux density. Magnetostriction causes audible noise if the magnetostriction is sufficiently large and the applied field is AC and in the audible frequency range, e.g. 50 or 60 Hz.

Mean Length Turn

The average length of a single turn in the winding of the device.

Oersted

The unit of magnetizing force in cgs units. One Oersted equals a magneto-motive force of one Gilbert per centimeter of path length. 1 Oersted = 79.58 A/m= 0.7958 A/cm

Percent Permeability (%)

Represents the percent change in permeability from the initial value.

Q factor

The Q factor or quality factor is a measure of the "quality" of a resonant system. Resonant systems respond to frequencies close to their natural frequency much more strongly than they respond to other frequencies. The Q factor indicates the amount of resistance to resonance in a system. Systems with a high Q factor resonate with a greater amplitude (at the resonant frequency) than systems with a low Q factor. Damping decreases the Q factor.

38 39

www.dongbucni.co.kr

Glossary of Terms

Search Coil

A coil inductor, usually of known area and number of turns, that is used with a fluxmeter to measure the change of flux linkage with the coil.

Single-Layer Winding

A winding for a toroidal core which will result in the full utilization of the inside circumference of the core without the overlapping of turns. The thickness of insulation and tightness of winding will affect results.

Surface Area

The effective surface area of a typical wound core available to dissipate heat.

Skin Effect

Skin effect is the tendency for alternating current to flow near the surface of the conductor in lieu of flowing in a manner as to utilize the entire cross-sectional area of tile conductor. The phenomenon causes the resistance of the conductor to increase. The magnetic field associated with the current in the conductor causes eddy currents near the center of the conductor which opposes the flow of the main current flow near the center of the conductor. The main current flow is forced further to the surface as the frequency of the alternating current increasing

Stored Energy

The amount of energy stored, in microjoules (10-6 joules), is the product of one-half the inductance (L) in microhenries (10-6 Henries), times the current (I)

squared in amperes.

Swing

A term used to describe how inductance responds to changes in cu r ren t . Examp le : A 2 :1 sw ing corresponds to an inductor which exhibits 2 times more inductance at very low current than it does at its maximum rated current. This would also correspond to the core operating at 50% of initial permeability (also 50% saturation) at maximum current.

Switch Mode Power Supply

A power conversion technique that involves breaking the input power into pulses at a high frequency by switching it on and off and re-combining these pulses at the output stage. Using this technique, an unregulated input voltage can be converted to one or more regulated output voltages at relatively high efficiencies.

Switching Frequency

The rate at which the DC input to a switching regulator is switched on and off.

Temperature rise

Change in temperature of a terminal from a no-load condition to full-current load. Also called T rise. (2) The increase in surface temperature of a component in air due to the power dissipation in the component. The power dissipation for an inductor includes both copper and core losses.

Estored = LI 221


38 39

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Dongbu CNI

Temperature Coefficient

A factor which describes the reversible change in a magnetic property with a change in temperature. The magnetic property spontaneously returns when the temperature is cycled to its original point. It usually is expressed as the percentage change per unit of temperature.

Temperature Stabilization

After manufacture, many types of soft and hard magnetic materials can be thermally cycled to make them less sensitive to subsequent temperature extremes.

Winding Factor

The ratio of the total area of copper wire inside the center hole of a toroid to the window area of the toroid.

Window Area

The area in and around a magnetic core which can be used for the placement of windings.

Glossary of Terms

40 41

Documents

02 Technical