Mag Design Formula

8/21/2019 Mag Design Formula

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DongbuFineChemicals

fl Inductance of Wound Cores

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

AmperesLaw: Thelaw isthemagneticequivalentofGaussslaw. Itrelatesthecirculatingmagneticfieldinaclosedlooptotheelectriccurrentpassingthroughtheloop

FaradaysLaw: Thelawthatdefinestherelationshipofthevoltageinducedacrossthewindingofacoretothefluxdensitywithinthecore

Magnetic Design Formula

L =Where L = induntance ( H)

= core permeabilityN = number of turns

A = core cross section area (cm2)

= mean magnetic path length (cm)L

N= inductance for Nturns ( H)

A L = 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 = 66102 10-3 = 6.60( H)

0.4 N2A10-2

Required N = desired L(nH)A

L(nH / N2)

0.4 NI

LN =AL N

2

106

L1

N1

fl Example) M040066A

L = = 6.60( H)0.4 125102 0.10010-2

2.380

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

H = (Amperes Law)

(Faradays Law)Erms 102

4.44fANBmax =

B

H=

2L2N2

2=

( )

1/2


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www.dongbufinechem.com

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

flInductance 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)L

N= 66102 10-3 = 6.60( H)

Where Rac = effective resistance (Ohm)a = hysteresis loss coefficientc = residual loss coefficiente = eddy current loss coefficient = same as before mentioned

L = inductanceBmax = maximum flux densityf = frequency

Eddy current loss

Residual loss

Hysteresis loss

Total loss factor

0.4 125102 0.10010-2

2.380

Rac

L

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

H = = = 15.8(Oe)0.4 N I

0.4 103

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)=6.60.85=5.6(H)

flCore loss

= aBmaxf + cf + ef2


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WindowArea =

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

fl Q Factor

Q =

Where Q = quality factor = 2 f (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 )V e = effective core volume (cm3)OD = core outer diameter before coating (cm)ID = core inner diameter before coating (cm)HT = core height before coating (cm)

L

Rdc + Rac+ Rd=

Reactance

Total Resistance

HT

Le = ( OD-ID )

flPhysical constant of core

InOD

ID

ID

2

V e = e 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

( )2

( )

Ae =OD-ID

2


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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:

flTemperature Rising Calculation

Temperature Rise(oC) =

Where /mhwf = mh for chosen winding factor

/mhu = unity value, listed for each core sizewf = chosen winding factorKwf = 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)

/mhu

wf

Kwf

Ku

fl Nominal DC Resistance

/mhwf=

The value of Rdcfor 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 factorKwf = length/turn for chosen wf*Ku = length/turn for unity(100%) wf*

* see Winding Turn Length on core size pages

Kwf

KuRdcwf = Rdcu wf

( )

0.833


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DongbuFineChemicals

Permeability vs. Frequency

flMPP10090

80

70

60

50

40

30

20

10

0100 1000 1000010

10

1426

60

147

173

200

1426

60

125

fl High Flux100

90

80

70

60

50

40

30

20

10

0100 1000 10000

Frequency (kHz)

Frequency (kHz)

160

125


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Permeability vs. Frequency

flSendust10098

96

94

92

90

88

86

84

82

80100 1000 10000

100

90

80

70

60

50

40

30

20

10

0

Frequency (kHz)

Power Flux

60

90

1426

356075

125

90

100 1000 10000

Frequency (kHz)


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DongbuFineChemicals

fl MPP

Normal Magnetizing curves

8000

7000

6000

5000

4000

3000

2000

1000

0

fl High Flux

1 10 100 1000

14000

13000

12000

11000

10000

9000

8000

7000

6000

5000

4000

3000

2000

1000

0

1 10 100 1000

Magnetizing Force (Oersteds)



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Normal Magnetizing curves

flSendust

16000

14000

12000

10000

8000

6000

4000

2000

01 10 100 1000



11000

10000

9000

8000

7000

6000

5000

4000

3000

2000

1000

0

fl Power Flux

1 10 100 1000


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DongbuFineChemicals

fl MPP

Permeability vs. AC Flux Density

4

3

2

1

0

-110 100 1000 10000

AC Flux Density (Gauss)

147 160 173

125

6026

fl High Flux30

25

20

15

10

5

0

-5

-1010 100 1000 10000


flSendust

4

3

2

1

0

-110 100 1000 10000


147 60

125

90

75

60

26

125

60

26


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Permeability vs. DC Bias Curves

flMPP10090

80

70

60

50

40

30

20

10

01 10 100 1000

100

90

80

70

60

50

40

30

20

10

01 10 100 1000

DC Mangnetizing Force (Oe)


200

160 125 60 26 14

173

160 147125 60 26 14

147

fl High Flux


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DongbuFineChemicals

Permeability vs. DC Bias Curves

flSendust10090

80

70

60

50

40

30

20

10

01 10 100 1000

100

90

80

70

60

50

40

30

20

10

01 10 100 1000



90 60

fl Power Flux

125 90 75 60 35 26 14


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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

147 -6.7333E-05 1.1333E-09 -7.1429E-05 2.7766E-08

160 -7.4336E-05 1.4404E-09 -8.3125E-05 3.1250E-08

173 -7.6087E-05 1.4485E-09 -8.6705E-05 3.3412E-08

200 -7.4578E-05 1.3375E-09 -8.2000E-05 4.5000E-08

a b c d

14 -7.6531E-06 -3.2799E-09 1.4286E-06 5.1020E-0926 -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

147 -4.5981E-05 5.6666E-10 -4.5578E-05 9.2554E-09

160 -4.9000E-05 6.1035E-10 -4.1250E-05 1.1719E-08

a b c d

MPP

High Flux

0

0

a

1 c d

b20

30

20

20

40

2

e f f


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DongbuFineChemicals

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

a b c d

60 -3.5444E-05 -1.8519E-10 6.6667E-07 8.3333E-0990 -5.4914E-05 8.2305E-10 -4.4444E-06 8.6420E-09

a b c d

Sendust

Power Flux

0

0

a

1 c d

b20

30

20

20

40

2

e f f


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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

147 -9.8980E-03 2.4490E-05 -1.0500E-02 6.0000E-04

160 -1.1894E-02 3.6875E-05 -1.3300E-02 8.0000E-04

173 -1.3163E-02 4.3353E-05 -1.5000E-02 1.0000E-03

200 -1.4916E-02 5.3500E-05 -1.6400E-02 1.8000E-03

k l m n

14 -1.0714E-04 -6.4286E-07 2.0000E-05 1.0000E-0626 -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

147 -6.7592E-03 1.2245E-05 -6.7000E-03 2.0000E-04

160 -7.8400E-03 1.5625E-05 -6.6000E-03 3.0000E-04

k l m n

MPP

High Flux

0

0

k l1Ratio of PermU

2

m n12


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DongbuFineChemicals

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

k l m n

60 -2.1267E-03 -6.6667E-07 4.0000E-05 3.0000E-0590 -4.9422E-03 6.6667E-06 -4.0000E-04 7.0000E-05

k l m n

Sendust

Power Flux

0

0

k l1Ratio of PermU

2

m n12


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Typical Core Loss of MPP

10000

MPP 14

Flux Density (Gauss)

PL=2.33F1.31B2.19

1000

100

10

1

0.110 100 1000 10000

10000

MPP 26


PL=1.39F1.28B1.29

1000

100

10

1

0.110 100 1000 10000

10000

MPP 125


PL=1.02F1.40B2.03

1000

100

10

1

0.1

10 100 1000 10000

10000

MPP 60


PL=0.64F1.41B2.20

1000

100

10

1

0.1

10 100 1000 10000


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DongbuFineChemicals

Typical Core Loss of MPP

10000

MPP 147,160,173,200


PL=1.08F1.40B2.04

PL

=C X Fa

X Bb

(F : kHz - B : kG)

1000

100

10

1

0.110 100 1000 10000

Perm C a b

14 2.33 1.31 2.19

26 1.39 1.28 1.29

60 0.64 1.41 2.20

125 1.02 1.40 2.03

147 1.08 1.40 2.04

160 1.08 1.40 2.04

173,200 1.08 1.40 2.04


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Typical Core Loss of High Flux

10000

HIgh Flux 14


PL=7.26F0.95B1.91

1000

100

10

1

0.1

10 100 1000 10000

10000

HIgh Flux 26


PL=3.19F1.22B1.08

1000

100

10

1

0.110 100 1000 10000

10000

HIgh Flux 125


PL=1.62F1.32B2.20

1000

100

10

1

0.110 100 1000 10000

10000

HIgh Flux 60


PL=3.65F1.15B2.16

1000

100

10

1

0.110 100 1000 10000


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DongbuFineChemicals

Typical Core Loss of High Flux

10000

HF 147,160


PL=1.74F1.32B2.10

PL

=C X Fa

X Bb

(F: kHz - B : kG)

1000

100

10

1

0.110 100 1000 10000

Perm C a b

14 7.26 0.95 1.91

26 3.19 1.22 1.08

60 3.65 1.15 2.16

125 1.62 1.32 2.20

147 1.74 1.32 2.10

160 1.74 1.32 2.10


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Typical Core Loss of Sendust

10000

Sendust 14


PL=3.18F1.21B2.09

1000

100

10

1

0.110 100 1000 10000

10000

Sendust 26


PL=2.27F1.26B2.08

1000

100

10

1

0.1

10 100 1000 10000

10000

Sendust 60,75,90,125


PL=2.00F1.31B2.15

1000

100

10

1

0.110 100 1000 10000

PL

=C X Fa X Bb

(F: kHz - B : kG)

Perm C a b

14 3.18 1.21 2.09

26 2.27 1.26 2.08

60,75,90,125 2.00 1.31 2.15


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DongbuFineChemicals

Typical Core Loss of Power Flux

Perm C a b

60, 90 4.79 1.25 2.05

10000

Power Flux 60, 90


PL=4.79F1.25B2.05

1000

100

10

1

0.110 100 1000 10000

PL

=C X Fa

X Bb

(F: kHz - B : kG)


22/30


Temperature Stability

flMPP3.0

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)

147 160 173 200

128

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

160

60

2614

147125

fl High Flux

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

Temperature (oC)


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DongbuFineChemicals

Temperature Stability

flSendust

125

90

75

90

60

14,26

60

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

flPower 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)


24/30


Symbol and Units

Symbol Discription Unit

Ae effctive 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 -


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DongbuFineChemicals

Glossary of Terms

AC flux density

Numberof flux l inesperunitof cross-sectional area

generated by an alternating magnetic field; Gauss

Air Gap

A non-magneticdiscontinuity ina ferro-magneticcircuit.

Forexample, thespacebetween thepolesof amagnet,

although fi lledwi thbrassofwoodofand othernon-

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 which avalanche

breakdown occurs in 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 inductorwhich is intended to fi lter, or 'choke', out

unwanted signals.

Copper Loss

The power lost by current flowing through the winding. The

power loss is equal to the square of the current multiplied

by theresistanceof thewire (I 2 X R). Thispower loss is

transferred into heat.

Core Losses

Core losses are caused by an altering magnetic field in the

corematerial. Thelossesarea functionof theoperating

frequency and the total magnetic flux swing. The total core

losses are made up of three main components: Hysteresis,

eddycurrentandresidual losses. These losses vary

considerably fromonemagneticmaterial toanother.

Applicationssuchashigherpowerandhigher frequency

switching regulators require careful core selection to yield

thehighest inductorperformancebykeeping thecore

losses to a minimum.

Core Saturation

The DC biascurrent flowing throughan inductorwhich

causes the inductance to drop by a specified amount from

the initial zero DC bias inductance value. Common specified

inductance drop percentages include 10% for ferrite coresand 20% for iron pow der cores in energy storage

applications. Also referred to as saturation current.

Curie Temperature

The temperatureatwhicha ferri tematerial loses its

magneticproperties. Thecore'spermeability typically

increases dramatically as the core temperature approaches

thecurie temperature, whichcauses the inductance toincrease. The permeability drops to near unity at the curie

temperature, which causes the inductance to drop

dramatically. Thecuriepoint is thetemperatureatwhich

the initial permeability (i) has dropped to 10% of its value

at room temperature.


26/30


Glossary of Terms

DC Bias

D irectcurrent (DC)applied to thew indingof acore in

addition toany time-vary ingcurrent. InductancewithDC

biasisacommonspeci fication forpowdercores. The

inductance w ill 'roll off'graduallyandpredictably 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

ofmeasure isohmsand i t isusually speci fiedasa

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 capacitance known

as thedistributedcapaci tance. Thecapac itance is in

parallel with the inductor. Thisparallel combinationwill

resonateatsomefrequency , which iscalled theself-

resonant frequency (SRF). Lowerdistributedcapacitance

for a given inductance will result in a higher SRF and vice

versa. (2) Capacitance that isnotconcentrated withina

lumpedcapacitor, butspreadoveracircuitorgroupofcomponents.

Eddy Current Losses

Core losses associated with the electrical resistivity of the

magnetic material and induced voltages within the material.

Eddy currentsare inversely proportional to material

resistivity andproportional to therateofchangeof flux

density. Eddycurrent lossesarepresent inboth 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.

Thiswill result ineddycurrents if themagneticcore

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 andhysteresis losses are the two major core loss factors. Eddy

current lossbecomesdominant inpowdercoresasthe

frequency increases.

Effective Permeability

For a magnetic circuit constructed with an air gap, or gaps,

thepermeabilityofahypothetical homogeneousmaterial

that would provide the same reluctance, or netpermeability.

EMC

Electromagneticcompatibility . Theabi lity ofanelectronic

device tooperate in its intendedenvironmentw ithout its

performance being affected by EMI and without generating

EMI that will affect other equipment.

EMI

Electro-Magnetic Interference-Anunwantedelectrical

energy in any form. EMI is often used interchangeably with

'noise' and 'interference'.


27/30

DongbuFineChemicals

Glossary of Terms

Flux Density (B)

Thecorrespondingparameter for the inducedmagnetic

field in an area perpendicular to the flux path. Flux density

is determined by the field strength and permeability of the

medium in which it is measured.

Full Winding

Awinding for toroidal cores that will result in45% of the

core's inside diameter remaining.

Harmonics

Energyat integral multiplesof the frequency of the

fundamental signal. Normallyexpressedas THD (Total

Harmonic Distortion) but can be specified for harmonics of

interest ineitherapercentageofordecibelsbelow the

power level of the fundamental frequency signal.

Hysteresis Loss

Hysteresismeans to lagbehind. This is the tendencyofa

magneticmaterial to retain itsmagnetization. Hysteresis

causes the graph of magnetic flux densi ty versus

magnetizing force (B-H curve) to form a loop rather than a

line. The area of the loop represents the difference between

energy storedandenergy releasedperunitof volumeof

material percycle. Thisdi fference iscalled thehysteresis

loss.

Hysteresis Loop

A closed curve obtained for a material by plotting

corresponding valuesof fluxdensity for theordinateand

magnetizing force for theabscissawhen thematerial is

passing through a complete cycle between definite limits of

eithermagnetizing forceor flux density. If thematerial 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 ForceCoerciveForce

Remanence

Flux Density

P

M

P

MaximumFlux DensityMaximum

Permeability

IntialPermeability


28/30


Glossary of Terms

Impedance

The total opposition offered by a component or circuit to the

flow ofalternatingor vary ing currentataparticular

frequency , includingboth theAC andD C component..

Impedance is expressed in ohms and is similar to the actual

resistance inadirectcurrentcircuit. Incomputations,

impedance ishandledasacomplex ratio of voltage to

current. Theohm istheunitof impedance. Impedance is

typically abbreviated as "z" or "Z". The frequency-invariant,

real component of impedance is resistance. The frequency-

variant, imaginary componentof impedance is reactance.

The reciprocal of impedance is admittance.

Inductance Factor (AL)

The inductance ratingofacore innanoHenriesper turn

squared (nH/N2) based on a peak flux density of 10 gauss (1

mT )at

a f

requen

cyof10 kHz. An

AL

va

lue

of40 wou

ldproduce400H of inductance for100 turnsand40mH for

1000 turns.

Initial Permeability

That valueof permeabi lityatapeak AC fluxdensity of10

gauss (1 mT).

Magnetic Energy

The product of the flux density (B) and the (de)magnetizing

force (H) inamagneticcircuitrequired to reach thatflux

density.

Magnetostriction

The expansion and contraction of a magnetic material with

chang ing magnetic flux densi ty. T he 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 densi ty .

Magnetostriction causes audible noise i f 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

Theaverage lengthofasingle turn in thewindingofthe

device.

Oersted

Theunitofmagnetizing force incgsunits. One Oersted

equals a magneto-motiv e force of one G i lbert per

centimeterofpath length. 1 Oersted =79.58 A/m=0.7958

A/cm

Percent Permeability (%)

Represents thepercentchange inpermeability 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

frequenciescloseto theirnatural frequencymuchmore

strongly than they respond toother frequencies. TheQ

factor indicates the amount of resistance to resonance in a

system. Systemsw ithahighQ factor resonatewitha

greater amplitude (at the resonant frequency) than systems

with a low Q factor. Damping decreases the Q factor.


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DongbuFineChemicals

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 fora toroidal corewhichwi ll result in the full

utilizationof the insidecircumferenceof thecorewithout

theoverlappingof turns. The thicknessof insulationand

tightness of winding will affect results.

Surface Area

The effective surface area of a typical wound core available

to dissipate heat.

Skin Effect

Skineffect is the tendencyforalternatingcurrent to flow

near thesurfaceof theconductor inl ieuof flowing ina

manner as to utilize the entire cross-sectional area of tile

conductor. Thephenomenoncauses the resistanceof the

conductor to increase. Themagnetic fieldassociatedwith

the current in the conductor causes eddy currents near the

center of the conductor which opposes the flow of the main

currentflow near thecenterof theconductor. Themain

current flow is forced further to thesurfaceas the

frequency of the alternating current increasing

Stored Energy

The amount of energy stored, in microjoules (10-6joules), is

theproductofone-halfthe inductance (L) inmicrohenries

(10-6 Henries), times the current (I) squared in amperes.

Swing

A termused to describehow inductance responds to

changes in current. Example: A 2:1 swing corresponds to an

inductor which exhibits 2 times more inductance at very low

current than itdoesat itsmaximumratedcurrent. This

would also correspond to the core operating at 50% of initial

permeability (also 50% saturation) at maximum current.

Switch Mode Power Supply

Apowerconversiontechnique that involvesbreaking the

input power into pulses at a high frequency by switching it

onandoffand re-combining thesepulsesat theoutput

stage. Using this technique, anunregulated input voltage

can be converted to one or more regulated output voltages

at relatively high efficiencies.

Switching Frequency

The rateatwhich the DC input toaswitchingregulator is

switched on and off.

Temperature rise

Change in temperatureofa terminal fromano-load

condition to full-current load. Alsocalled T rise. (2) The

increase in surface temperature of a component in air due

to thepowerdissipation in thecomponent. Thepower

dissipation foran inductor includesbothcopperandcore

losses.

Estored = LI2

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Glossary of Terms

Temperature Coefficient

A factorwhich describes thereversiblechange ina

magneticpropertywi thachange in temperature. The

magneticproperty spon taneously returnswhen the

temperature iscycledto itsoriginal point. Itusually is

expressed as the percentage change per uni t o f

temperature.

Temperature Stabilization

After manufacture, many types of soft and hard magnetic

materialscanbe thermally cycled tomake theml ess

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.

Documents

Mag Design Formula