Energy Efficiency of Amorphous Metal Based Transformers

R. HasegawaMetglas, Inc

440 Allied Drive, SC 29526 USA

October 2004

OVERVIEW•Basics•Introduction

Amorphous versus crystalline magnetic materialProperties of amorphous magnet - why amorphous ?Exchange Interaction and MagnetizationMagnetic Anisotropy, Magnetostriction, Magnetic Domain and StructureB-H Characteristics and Magnetization ProcessesMagnetic Losses

•ApplicationsElectric Power TransformersHigh Frequency Power ElectronicsTelecommunicationPulse Transformers and Pulse Power DevicesMagnetic Sensors and Electronic Article SurveillanceAutomotive MagneticsMedical ApplicationsMagnetic Shielding

FUNDAMENTALS

CASTINGTo achieve an amorphous structure in a metallic solid, one has to

solidify the molten metal before constituent atoms take their positions in a crystalline atomic structure. The required rate for molten-metal cooling is about one million degrees Celsius per second for most of the amorphous

metal we are interested in. The schematic drawing shown below is a method we use to mass-produce amorphous metal in our company.

FUNDAMENTALS

ATOMIC STRUCTURE & MAGNETIC PROPERTIES

AmorphousCrystalline

•Ordered structure→ magnetocrystalline anisotropy

•Polycrystalline structure→ higher coercivity

These features do not help for easier magnetization and demagnetization.

•Random network of atoms→ lack of crystalline anisotropy

•Absence of phase boundaries→ lower coercivity

These features lead to faster flux reversal.

ATOMIC STRUCTURE - AMORPHOUS

FUNDAMENTALS OF AMORPHOUS METAL

Electrical PropertiesThe electrical resistivity of many amorphous metals ranges from about 100 to 150 µΩ-cm. This is two-to-three times higher than

that of silicon steel or Fe50-Ni50 alloy, which is partially responsible for low core losses in these metals.

The temperature coefficient of the resistivity is relatively low and can reach nearly zero in some of the Fe-based alloys.

Mechanical PropertiesAmorphous metals are hard with Vickers hardness ranging from about 700 to 1000, but mechanically ductile in the as-cast state.

Elastic modulus is about 60x109 N/m2 .Thermal expansion coefficient is about 6-13 ppm/oC.

MAGNETIZATION PROCESS AND CORE LOSS

Magnetization processes are via uniform rotation ( high frequency limit) and domain wall motion (low frequency limit).Macroscopic magnetic loss (e.g. core loss) arises from eddy current (caused by magnetization rotation) and hysteresis behavior (caused by domain wall motion).

Empirically we find:

Core Loss = a B 1.5-2 f + b B 1.5-2.5 f 1.5-2

Core Loss /f = a B 1.5-2 + B 1.5-2 f 0.5-1.0

(loss separation)

0.1 1 10 100 10000.001

0.01

0.1

1

10

100

1000

Frequency (kHz)

Cor

e Lo

ss

(W/k

g)

Supermalloy25 µm

METGLAS 2714A25 µm

H7C4 (ferrite)(estimated)

Supermendur100 µm

Deltamax50 µm

METGLAS SA-125 µm

Bmax=0.2T

FUNDAMENTALS

SOFT MAGNETIC PROPERTIES

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-3 -2 -1 0 1 210 10 10 10 10 10

Fe-50Co

Carbon SteelFe--

Soft Ferrites

PermalloyPowder

Fe-3SiFe-6.5Si

Fe-baseAM

Fe-(40-50)Ni

Fe & Fe

Alloy Powder

Fe-Ni base AM

Co-baseAM

Fe-(70-80)Ni

Coercivity (A/cm)

Saturation Induction (T)

⋅

2

3

4

5

6

7

-3 -2 -1 0 1 2

10

10

10

10

10

1010 10 10 10 10 10

• Supermalloy

• Sendust

• 78 Permalloy

Ni-Zn Ferrite• Fe-3Si

• Hipernik

Mg-ZnFerrite

• Fe

Co-base AM

Fe-Ni base AM

Fe-base AM

Coercivity (A/cm)

Relative Permeability

FUNDAMENTALS OF AMORPHOUS METAL

Why amorphous versus crystalline soft magnets ?

Examples: Effects of Field AnnealingB

H

LONGITUDINAL TRANSVERSE

FUNDAMENTALS OF MAGNETICS

• Why amorphous versus crystalline soft magnets ?

Amorphous Metals exhibit:- easier magnetization (low coercivity and high permeability);- lower magnetic loss (low coercivity, high permeability and high

resistivity);- faster flux reversal (as a result of low magnetic loss)- versatile magnetic properties resulting from post-fabrication

heat-treatments and a wide range of adjustable chemicalcompositions.

ELECTRICAL POWER APPLICATIONS

Three basic families of amorphous soft ferromagnets

Fe-Base (e.g. METGLAS2605SA1)Main Application: Distribution Transformer

ELECTRICAL POWER APPLICATIONS

• High saturation induction and low core losses at 50/60 Hz are

required for electrical transformer applications.

• Amorphous metal-based transformers have 75-80% lower core

losses than crystalline Fe-Si base units under linear loads. When

higher harmonics are present, the difference in core losses becomes

even greater.

• Load losses are still less than Fe-Si based transformers.

• Significant savings can be achieved when existing Fe-Si based

transformers are replaced by amorphous metal-based units.

• The energy efficiency translates to reduced emission of

hazardous gasses such as CO2, SO2, etc.

NO LOAD LOSSES

Amorphous vs SiFe Steel Transformers

Core Loss (W)Transformer

Rating Silicon SteelIn Service Best

Amorphous MetalLoss

Reduction%

50 kVA, 1-Phase

300 kVA, 3-Phase

210

1000

35

165

75 to80%

105

500

TRANSFORMER LOSS

Amorphous vs SiFe Steel Transformers

96.0%

96.5%

97.0%

97.5%

98.0%

98.5%

99.0%

99.5%

100.0%

0% 25% 50% 75% 100% 125% 150%

Load

% E

ffic

ien

cy

Amorphous Metal

2000 kVA Transformer Efficiency

Conventional

TRANSFORMER EFFICIENCY

IMPACT ON Co2 GAS GENERATION

0

2 000

4 000

6 000

8 000

10 000

12 000

14 000

16 000

18 000

20 000

0% 25% 50% 75% 100%

Load

Wat

ts

UltraGlas Other Cast Coil

Other Cast CoilUltraGlas

2000 kVA ComparisonWatt Rating

Average LoadingRange - Commercialand Industrial

AMORPHOUS METAL TRANSFORMERS & TOTAL HARMONIC DISTORTION

“ Build-In” Superior Performance for Harmonic Conditions

What Are Harmonics And Where Are They Found ?

Adjustable Speed Motor Drives

UPSHID Lighting

PCs

“Pure” Power“Distorted” Power

-200

-150

-100

-50

0

50

100

150

200

0

0

Commercial &Industrial

Utility Generation

24 kV 765 - 236 kV

Transmission

230 - 34.5 kV

Subtransmission

Step Down

34.5 - 1.2 kV

Primary Distribution

Secondary Distribution

< 1.2 kV

Substation DistributionStep Up

Harmonics Basics

5th Harm(300 Hz) =79.5 Amp RMS

-150

-100

-50

0

50

100

150

0 0.004 0.008 0.012 0.016

fundamental =100 Amp RMS

-200

-150

-100

-50

0

50

100

150

200

0 0.004 0.008 0.012 0.016

7th Harm(420 Hz) =66 Amp RMS

-150

-100

-50

0

50

100

150

0 0.004 0.008 0.012 0.016

ASD Line Current =143.8 Amp RMS

-400

-300

-200

-100

0

100

200

300

400

0 0.004 0.008 0.012 0.016

Any periodic waveform can be considered as a summation of sinusoidal waveform of

different discrete frequencies

500 KVA Transformer Loss Study

0

2

4

6

8

10

12

14

16

18

20

22

24

0 0.2 0.4 0.6 0.8 1 1.2

Tota

l Los

ses

(kW

)

Actual hourly and weekday/weekend data

Expected losses based on laboratory NL and LL tests

AM AM

SiFe

SiFe

Total Loss Increase: ~100 % (Amorphous) ; ~300 % (SiFe)

Load Ratio

% o

f Fun

dam

enta

l2

67

40

7 7 4 20

20

40

60

80

100

3 5 7 9 11 13 15

Harmonic #

75 % THD

Laboratory Test Data on Harmonics Effects on No Load Losses(30 kVA Units with Identical Coils)

50 80

230

770

0

100

200

300

400

500

600

700

800

900

"Pure" Power w/ 75% THD

No

Load

Los

s (W

)

AMTSiFe

No-Load Loss Increase: 60% (Amorphous) ; 235% (Silicon Steel)

250 KVA Transformer Losses @ ~56% Loading ERDA Industrial Site Field Tests

966

1553

1084

1671

155

155

33

74

311

698

99

99

0

500

1000

1500

2000

2500

3000

Expected AMT Actual AMT Expected CRGO Actual CRGO

Loss

es (W

)

Core Eddy CurrentCore HysterisisCoil

AM Increase - 41 W SiFe Increase - 387 W

AMT Performance under Harmonics

Eddy Current Losses Increase in Both the Core and Coil, but Much Less for the Amorphous Core

Harmonic Impact on Transformer Losses

Total Harmonic Distortion = (Σ in2)1/2 / i1in : n-th harmonic current

Magnetic Loss = A f + B dl fm Bn /ρ(A, B : constant)

~ 2~ 2n

~ 2~ 1.5m

21-2l

200 µm~ 20 µmd (thickness)

~ 50 µΩ-cm~ 130 µΩ-cmρ(resistivity)

Silicon SteelAmorphous MetalProperty/Exponent

Smaller thickness and higher resistivity coupled with smaller exponent m leadto lower magnetic loss at higher frequencies in amorphous transformer cores.

Harmonic Impact on Transformer Losses -250 kVA

A. Harmonic Content (THD~25%)

5169110201100Content (%)

1715131197531Harmonics

B. Transformer Losses without Harmonic Distortion

1,5501,098Total Transformer Loss

5855Loading Level (%)

1,084966Coil Loss

466132Total Core Loss

31133Eddy Current

15599Hyteresis

Silicon SteelAmorphous MetalLoss (W)

C. Transformer Losses with Harmonic Distortion of Table A

2,5241,726Total Transformer Loss

5855Loading Level (%)

1,6711,553Coil Loss

853173Total Core Loss

69874Eddy Current

15599Hyteresis

Silicon SteelAmorphous MetalLoss (W)

Harmonic Impact on Transformer LossesTwofold Effect

• INCREASES NO-LOAD LOSS• DECREASES POWER FACTORVOLTAGE DISTORTION

• INCREASES WINDNG LOSS• INDUCES VOLTAGE DISTORTION,INCREASING NO-LOAD LOSS

CURRENT DISTORTION

Direct Consequences:

• Very High Total Transformer Losses – much higher than spec values

• Transformer Failure / Electrical Fire

Associated Problems:

• Deterioration of Electrical Power Quality

• Extra Energy Cost – Decreased Distribution Capacity

• No Need for Added Devices such as Isolation Transformers, Harmonic Filters

• Impact of THD on Transformer Losses (examples) •Transformer Loss Increase (THD=75%): 60-100 % (Amorphous); 200-300 % (Silicon Steel)

•Transformer Loss Increase (THD=25%): 57 % (Amorphous); 63% (Silicon Steel)

• Increased Energy-Savings (Example: 500 kVA , unit price at $7,500)

Condition Energy Consumption Annual Savings (@$.125/kWh)• Without Harmonics 20,000 kWh/y $2,500 (Payback: 3 years)

• With Harmonics 130,000 kWh/y $16,250 (Payback: 0.5 year)

• Worldwide Annual Electrical Energy Savings (current estimate)• Without Harmonics ~125 TWh ($16 billion) ~100 million tons of CO2 gas reduction

• With Harmonics ~220 TWh ($28 billion) ~170 million tons of CO2 gas reduction

Solution to THD Problemsusing Amorphous Metal-based Transformers

“Electrical power pollution is costing US businesses $26 B/y in damage and prevention. By the year 2000, 60 % of all electricity will be passing through nonlinear loads.” - Business Week

CONCLUSIONS

• Under pure ‘sinusoidal’ excitation, amorphous metal-based transformers exhibit about ¼ of the no-load loss of a high-grade silicon-steel. This corresponds to an annual worldwide potential savings of about 125 TWh and annual reduction of CO2 emission of about 100 million tons.

•Under harmonic conditions which are the actual conditions we are in, potential energy savings are considerably higher than the above. The energy savings is estimated at ~220 TWh.

•Worldwide use of amorphous metal-based transformers, therefore, will help us reduce fossil-fuel dependency and create cleaner environment with higher air quality.