Magnetics-powder-core-material-developments.pdf

New Powder Core Materials for High Frequency and High Current

Mark A. Swihart VP – Technology and Product Development

Magnetics’ Powder Core Materials

Type

Alloy Composition

Available Perms Core Loss (mW/cm3 @ 100 kHz, 100 mT)

Perm vs. DC Bias (Oe) 50% of µi

Relative Cost

Kool Mµ

75 Series

XFlux®

Kool Mµ® MAX

High Flux

MPP

Sendust

Blend

6.5% Silicon Iron

Sendust

High Flux

MPP

Iron / Silicon / Aluminum

Iron / Silicon / Aluminum

6.5% Silicon Iron

Iron / Silicon / Aluminum

50% Nickel Iron

Permalloy

14-125

26-60

19-90

19-60

14-160

14-300

550

1200

1350

550

625

450

96

150

165

130

185

106

1x

1.1x

1.2x

2x

4x-6x

7x-9x

Material Comparison Property

Best

→

→

→

→

Weakest

µ vs. DC Bias

High Flux

XFlux

75 Series

Kool Mµ MAX

MPP

Kool Mµ

AC Core Loss

MPP

Kool Mµ MAX

Kool Mµ

75 Series

XFlux

High Flux

Kool Mµ

75 Series

XFlux

Kool Mµ MAX

High Flux

MPP

MPP

Kool Mµ MAX

Kool Mµ

High Flux

75 Series

XFlux

XFlux

75 Series

Cost µ vs. Temp Stability

200°C continuous use for all materials

Temperature Rating Range of Available Perms

MPP

High Flux

Kool Mµ

Kool Mµ MAX

Inherent Advantages of Powder Cores 1. Soft Saturation Curve Discrete Gap

Distributed Gap

(Ferrite)

(Powder Core)

Sharp Saturation

Soft Saturation

Lower material Bmax

Higher material Bmax

Design for minimal shift – lower IPeak

Design for shift – higher IPeak

Fault condition risk

Inherent fault tolerance 5

DC Bias - Powder Core vs. Gapped Ferrite 1.0

Per Unit of Initial Permeability

0.9

60 permeability Kool Mµ

0.8 0.7 0.6 0.5 0.4

Ferrite gapped to an effective permeability of 60

0.3 0.2 0.1 0.0 1

10

100

1000

DC Magnetizing Force (Oersteds) 6

Operating Design Point The gapped ferrite must be kept a safe distance away from the sudden rolloff. Small shifts in the rolloff curve, or in the operating point, could have a FERRITE

disastrous effect. This curve shifts to the left with increasing temperature.

INDUCTANCE

POWDER CORE

The powder core is safely designed to operate part way down the curve. The curve does not shift significantly with increasing temperature.

CURRENT

Ferrite Current

Powder Core Current

7

Magnetization Curves Bsaturation

No Gap

Distributed Gap No Gap

Discrete Gap

Bsaturation Powder Core Advantages: 1. Higher Bsaturation 2. Softer Saturation 3. Full saturation at high temperature (not shown)

8

Comparison of 60µ Cores

9

Inherent Advantages of Powder Cores 2. Temperature Stability Discrete Gap

Distributed Gap

(Ferrite)

(Powder Core)

Low Curie Temp

High Curie Temp

Bmax lower at high temp Bmax flat to high temp DC bias lower at temp

DC bias same at temp

10

Alloy Saturation Curves vs. Ferrite 16

HIGH FLUX

14 12 10

Saturation 8 Flux Density 6 in kG

MPP

4

FER RITE

2 0 -50

0

50

100

Temperature °C

150

200

11

DC Bias and Temperature Per Unit of Initial Permeability

1.0 MPP, 250C 0 and 75 C

0.9 0.8 0.7 0.6 Ferrite 750C

0.5 0.4

Ferrite 250C

0.3 0.2 0.1 0.0 1

10

Hdc (Oersteds)

100 12

Inherent Advantages of Powder Cores 3. Leakage, EMI, and Fringing Flux Discrete Gap

Distributed Gap

(Ferrite)

(Powder Core)

EMI effects from gap(s)

Minimized EMI effects, particularly for self-shielded toroids

Losses from fringing flux at gap, No fringing effect particularly for high current (large gaps) High µ material–minimal Low µ material–near field leakage leakage at the surface effects at the surface 13

Fringing Flux / Leakage Flux Ferrite

Powder Core

14

Fringing Losses Flux bowing into the space occupied by copper conductor generates eddy current losses in the coil. The fringing losses can easily exceed the AC core losses. The effect is worst at low effective permeability, in other words when the gap is large due to high current in the inductor.

15

Inductor Core Loss Comparison Frequency

10 kHz

100 kHz

500 kHz

1 MHz

Ferrite*

1X

1X

1X

1X

MPP

2X

5X

9X

12X

Kool Mµ MAX

2X

5X

10X

15X

Kool Mµ

2X

6X

15X

20X

High Flux

5X

10X

30X

30X

*Excluding fringing losses at the gap. A medium to large gap on a ferrite center leg may cause total losses that are dominated by fringing loss.

16

Steinmetz Equation for General Magnetic Loss a

Pv = k f B

b

Pv is core loss density f is frequency B is flux density k, a, and b are constants a will be between 1 and 2 b will be between 2 and 3 Controlling high frequency losses is unavoidably about controlling AC flux density. 17

Improved High Flux • Cores with 58+ properties manufactured beginning January 2018 • No change to existing High Flux part numbers Perm

26

60

125

Material

Perm vs. DC Bias (Typ.)

Core Loss

(Oersteds)

(mW/cm3 @ 100 mT, 100 kHz)

80%

50%

Typical

Limit

58+

240

425

900

1250

Previous

197

385

1800

2500

58+

101

185

625

900

Previous

87

165

900

1600

58+

53

93

800

1000

Previous

43

83

900

1450

Kool Mµ MAX • Superior DC Bias performance and lower losses than standard Kool Mµ • Lower cost compared with MPP and High Flux.

00 79 050 A7

General Information Permeability

19µ, 26µ, 40µ, 60µ

Alloy Composition

Fe/Si/Al

Saturation Flux Density

1 Tesla

Curie Temperature

500°C

Operating Temperature Range

-55 to 200°C

OD Size Range (mm)

13.5 - 134

26µ also available in blocks

Core finish code Catalog Number (size) Material Code (79 = Kool Mµ MAX)

Grading Code

Kool Mµ MAX - Performance Comparison DC Bias at x Ls (Oe)

Core Loss (mW/cm3)

Cost Ratio

Material (60µ) 80%

50%

W100 mT, 50 kHz

W100 mT, 100 kHz

Price Scale

Kool Mµ® MAX

68

135

190

500

2.0

Kool Mµ®

43

95

210

550

1.0

XFlux®

89

175

680

1550

1.5

High Flux

87

165

350

900

4.0

MPP

60

106

175

450

7.0

Kool Mµ and Kool Mµ MAX alloy - Sendust

Kool Mµ MAX – DC Bias Performance

Kool Mµ MAX – AC Loss Performance

Kool Mµ MAX vs. Kool Mµ - DC Bias

Kool Mµ MAX vs. Kool Mµ - Core Loss

100 kHz

Kool Mµ MAX - Core Sizes

Size

Dimensions (after finish)

Magnetic Data

OD max (mm)

ID min (mm)

HT max (mm)

Wa (mm2)

Ae (mm2)

Le (mm)

Ve (mm3)

050

13.5

6.98

5.52

38.3

10.9

31.2

340

120

17.3

9.52

7.12

71.2

19.2

41.2

791

380

18.1

9.01

7.12

63.8

23.2

41.4

960

206

21.1

12

7.12

114

22.1

50.9

1,120

310

23.7

13.3

8.3

139

31.7

56.7

1,800

350

24.4

13.7

9.66

149

38.8

58.8

2,280

930

27.69

14.1

12

156

65.4

63.5

4,150

548

33.66

19.4

11.5

297

65.6

81.4

5,340

585

35.18

22.5

9.78

399

46.6

89.5

4,150

324

36.71

21.5

11.4

364

67.8

89.8

6,090

254

40.77

23.3

15.4

427

107

98.4

10,600

438

47.63

23.3

19

427

199

107

21,300

089

47.63

27.88

16.2

610

134

116

15,600

715

51.69

30.93

14.4

751

125

127

15,900

195

58.0

25.6

16.2

514

229

125

28,600

109

58.0

34.7

14.9

948

144

143

20,700

620

62.9

31.7

25.9

789

360

144

51,800

740

75.0

44.4

35.9

1,550

497

184

91,400

866

78.9

48.2

13.9

1,820

176

196

34,500

906

78.9

48.2

17.1

1,820

221

196

43,400

102

103.0

55.75

17.9

2,470

358

243

86,900

337

134.0

77.19

26.8

4,710

678

324

220,000

XFLUX • 0078xxx-A7 series • Cost 40-50% less than High Flux • Applications: • Low & medium frequency chokes, where inductance at peak current is critical. • Where High Flux would be used but cost is a constraint.

• Where iron powder would be used but iron powder losses are unacceptably high, or the design cannot tolerate thermal aging.

XFlux

– 75µ and 90µ

Now available in 050 (13.5mm OD) to 337 (134mm OD) size toroids.

Custom Blending • Powder blends give intermediate performance for permeability, saturation, and losses. • Blending can be useful for: • Fine tuning a material’s performance

• Decreasing overall cost (in trade for some performance) • Making a powder better to work with, especially at pressing • Arriving at a target particle size distribution

75 (Blended) Material • Customized by customer and application. • Target bias, inductance and loss defined in special specs.

Thank you! Planning to attend PCIM 2019? We will be discussing this same topic in the Exhibitor Forum on Wednesday, 8 May from 14:00-14:20. Hope to see you there!