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Magnetic Materials

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Hysteresis Loop for Ferromagnetic Materials

Brremnant flux or residue flux

Hc coercive flux or coercivity

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Magnetization Curves for Hard Materials (I)

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Magnetization Curves for Hard Materials (II)

1T = 10 kGauss, 1A/m = 0.01257 Oe or 1 Oe = 79.6 A/m

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From Yeadon Handbook of Small Electric Motors

Hard Magnetic Material Properties

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Hard Material Circuit Analysis (1)

Load line:

Device line:Bm=(Br/Hc)(Hm+Hc)

= rHm +Br

mmm dHF gHgg F

0 gm FF

0 gHdH gmm

mm

g Hg

dH

m

m

gg Hg

d

HB 00

md

B

+

_

mF

Actual direction ofHm

g

grB

cH mH

gm BB

H

B

cross section areaAm

cross section areaAg

mmgg ABAB From

m

g

gm

A

ABB

From magnetic circuit

mm

gm

m HA

A

g

d

B 0

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Hard Material Circuit Analysis (2)

mm

g H

g

dB 0

grB

cH mH

gm BB

H

H

mmgg ABAB Fromg

mmg

A

ABB

From )(00

2

mmg

mm

gm

m

g

BHgA

AdBH

g

dB

magVol

gapVol2

0

gap

mag)(

VolVol g

mm

BBH

The required volume of magnet can be minimized by operating the magnet at

the point of maximum BH (or energy) product.

Device line:Bm= rHm +Br

md

B

+

_

mF

Actual direction ofHm

g

cross section areaAm

cross section areaAg

maximum BH product

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Hard Material Equivalent Circuit

0m r r mB B H

0

0

m m r m r m m

mr r m m

m

B A B A A H

A d Hd

r r mB A 0

mm

r m

d

A R

mr

m

R

F

m m mH dF

whereLoad Line:

0

0

gmm m

m

c m

AdB H

g A

P H

1 1.2r

Pc is called permeance coefficient

/

/

g g gm mc

m m m g m

A A gdP

g A A d

R

R

P

P md

r

mF

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Loaded PM Circuit

B

0H0 cH

rB

0 mRH

mRB

m m gH d H g Ni

m m g gB A B A

0 0

0

g g g

m g g c mm m m

A A A NB B H P H i

A A A g

mg m

d NiH H

g g

AC load line

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Special Operation of Hard Material

(a) Operation at remanence (S.C.);

(b) Operation at coercivity (O.C.)

D. Hanselman,Brushless Permanent magnet Motor Design, 2ndEdition,

p. 36, Magna Physics Publishing, 2006.

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Influence of Temperature

0 0( ) ( ) ( )r r BB T B T T T

D. Hanselman,Brushless Permanent magnet Motor Design, 2ndEdition,

p. 37, Magna Physics Publishing, 2006.

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Soft Magnetic Materials

Ferrite materials

Carbon steels Silicon steels

High saturation alloys

Amorphous ferromagnetic alloys Soft magnetic powder composites

Nanostructured materials

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Soft Magnetic Material Properties

From Yeadon Handbook of Small Electric Motors

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Ferrite Materials (1)

3C81 is from Philips, USA.

Philips Components, 3C81Material Grade Specification, 1997

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Ferrite Materials (2)

3F3 is from Philips, USA.

Philips Components, 3F3Material Grade Specification, 2000

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Ferrite Materials (3)

4F1 is from Philips, USA.

Philips Components, 4F1Material Grade Specification, 2000

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Carbon Steel 1008

www.eng-tips.com Magnetic Engineering Forums

Maxwell SV Software

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Carbon Steel 1010

www.eng-tips.com Magnetic Engineering Forums

Maxwell SV Software

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Carbon Steel 1018

www.eng-tips.com Magnetic Engineering Forums

Maxwell SV Software

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Nonoriented Silicon Steel

J. F. Gieras,Advancements in Electric Machines, Springer, 2008.

M-19 means core losses shall be below 1.9 W/lb at 1.5 T and 60 Hz.

Fe-Si alloys with random orientation of crystal cubes and practically have the same

properties in any direction in the plane of the sheet.

Armco M-19

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Armco M-27, 36 and 43

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High Frequency Electric Steel (1)

To reduce core loss, laminations with thin gauges are manufactured.

ArnonTM 5 is fromArnold Magnetic Technologies Corp., Rochester, NY, USA.

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High Frequency Electric Steel (2)

Cogent Power Ltd., Newport, UK. www.cogent-power.com

J. F. Gieras,Advancements in Electric Machines, Springer, 2008.

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High Saturation AlloysFe-Co alloys with Co contents from 15 to 50% have the highest known

saturation flux density and highest Curie temperature of any alloy family..

Hiperco50 is from Carpenter, USA.

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Hiperco50 Core Loss

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Vacoflux50 B-H curveVacoflux50 is from Vacuumschmelze, Hanau, Germany.

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Amorphous Ferromagnetic Materials (1)

J. F. Gieras,Advancements in Electric Machines, Springer, 2008.

www.ammtechnologies.com

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Amorphous Ferromagnetic Materials (2)

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Soft Magnetic Powder Composites (1)

Soft magnetic powder composites are composed of iron powder, dielectric

(epoxy resin) and filler (glass or carbon fibers) for mechanical strengthening.

Accucore from TSC Ferrite International, Wadsworth, IL. www.tscinternational.com

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Soft Magnetic Powder Composites (2)

SomaloyTM500 from Hgans, Sweden.

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Soft Magnetic Powder Composites (3)

SomaloyTM500 from Hgans, Sweden.

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Soft Magnetic Nanocrystalline Composites