Energy Efficiency of
Amorphous Metal Based Transformers
R. Hasegawa
Metglas, Inc
440 Allied Drive, SC 29526 USA
October 2004
OVERVIEW
•Basics
•Introduction
Amorphous versus crystalline magnetic material
Properties of amorphous magnet - why amorphous ?
Exchange Interaction and Magnetization
Magnetic Anisotropy, Magnetostriction, Magnetic Domain and Structure
B-H Characteristics and Magnetization Processes
Magnetic Losses
•Applications
Electric Power Transformers
High Frequency Power Electronics
Telecommunication
Pulse Transformers and Pulse Power Devices
Magnetic Sensors and Electronic Article Surveillance
Automotive Magnetics
Medical Applications
Magnetic Shielding
FUNDAMENTALS
CASTING
To 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
Crystalline
Amorphous
•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 Properties
The 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 Properties
Amorphous 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:
1000
Core Loss = a B 1.5-2 f + b B 1.5-2.5 f 1.5-2
Supermendur
100 µm
Deltamax
50 µm
100
METGLAS SA-1
25 µm
1.5-2
Core Loss /f = a B
+B
(loss separation)
1.5-2
f
0.5-1.0
Core Loss
(W/kg)
10
1
Supermalloy
25 µm
0.1
METGLAS 2714A
25 µm
0.01
Bmax=0.2T
0.001
0.1
1
10
Frequency (kHz)
H7C4 (ferrite)
(estimated)
100
1000
FUNDAMENTALS
SOFT MAGNETIC PROPERTIES
Relative Permeability
Saturation Induction (T)
3.0
7
10
Co-base AM
6
10
5
10
⋅
•
4
Fe-base AM
3
10
•
•
•
2
10 -3
10
-2
10
-1
10
10
Coercivity (A/cm)
Fe-(40-50)Ni
Fe-Ni base AM
1.0
Permalloy
Powder
Fe-(70-80)Ni
1
10
Co-base
AM
0.5
Mg-Zn
Ferrite
Fe
0
Fe &
Fe
Alloy
Powder
Fe-base
AM
1.5
78 Permalloy
Hipernik
Ni-Zn Ferrite
• Fe-3Si
Fe-- Carbon Steel
Fe-3Si
Fe-6.5Si
2.0
Supermalloy
Fe-Ni base AM
• Sendust
10
Fe-50Co
2.5
2
10
Soft Ferrites
0.0
10
-3
10
-2
-1
10
10
0
Coercivity (A/cm)
1
10
2
10
FUNDAMENTALS OF AMORPHOUS METAL
Why amorphous versus crystalline soft magnets ?
Examples: Effects of Field Annealing
B
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 chemical
compositions.
ELECTRICAL POWER APPLICATIONS
Three basic families of amorphous soft
ferromagnets
Fe-Base (e.g. METGLAS2605SA1)
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
Transformer
Rating
Core Loss (W)
Silicon Steel
In Service
Amorphous Metal
Best
50 kVA, 1-Phase
210
105
35
300 kVA, 3-Phase
1000
500
165
Loss
Reduction
%
75 to
80%
TRANSFORMER LOSS
Amorphous vs SiFe Steel Transformers
TRANSFORMER EFFICIENCY
100.0%
99.5%
Amorphous Metal
% Efficiency
99.0%
98.5%
Conventional
98.0%
97.5%
2000 kVA Transformer Efficiency
97.0%
96.5%
96.0%
0%
25%
50%
75%
Load
100%
125%
150%
IMPACT ON Co2 GAS GENERATION
2000 kVA Comparison
Watt Rating
20 000
18 000
Average Loading
Range - Commercial
and Industrial
16 000
14 000
Watts
12 000
10 000
8 000
UltraGlas
Other Cast Coil
6 000
4 000
2 000
UltraGlas
Other Cast Coil
0
0%
25%
50%
Load
75%
100%
AMORPHOUS METAL TRANSFORMERS &
TOTAL HARMONIC DISTORTION
“ Build-In” Superior Performance for Harmonic
Conditions
What Are Harmonics And Where Are They Found ?
“Distorted” Power
“Pure” Power
Adjustable Speed
Motor Drives
UPS
HID Lighting
PCs
200
150
100
50
0
-50
0
-100
-150
-200
24 kV
Utility
Generation
0
Step Up
Step Down
Substation
Distribution
765 - 236 kV
230 - 34.5 kV
34.5 - 1.2 kV
< 1.2 kV
Primary
Distribution
Secondary
Distribution
Transmission Subtransmission
Commercial &Industrial
Harmonics Basics
Any periodic waveform can be considered as
a summation of sinusoidal waveform of
different discrete frequencies
fundamental =100 Amp RMS
200
150
100
50
0
-50
0
0.004
0.008
0.012
ASD Line Current =143.8 Amp RMS
0.016
-100
400
-150
300
-200
200
100
5th Harm(300 Hz) =79.5 Amp RMS
0
150
-100
100
-200
50
-300
-400
0
0
0.004
0.008
0.012
0.016
-50
-100
-150
7th Harm(420 Hz) =66 Amp RMS
150
100
50
0
0
-50
-100
-150
0.004
0.008
0.012
0.016
0
0.004
0.008
0.012
0.016
500 KVA Transformer Loss Study
Total Loss Increase: ~100 % (Amorphous) ; ~300 % (SiFe)
24
22
Actual hourly and
weekday/weekend data
20
SiFe
Total Losses (kW)
18
16
14
Expected losses based on
laboratory NL and LL tests
12
10
SiFe
8
6
AM
AM
4
2
0
0
0.2
0.4
0.6
Load Ratio
0.8
1
1.2
Laboratory Test Data on Harmonics Effects on No Load Losses
(30 kVA Units with Identical Coils)
100
900
700
770
AMT
SiFe
600
500
400
300
230
50
Harmonic #
60
75 % THD
40
40
2
80
7
7
9
11
4
2
13
15
0
0
"Pure" Power
67
20
200
100
80
% of Fundamental
No Load Loss (W)
800
w/ 75% THD
3
5
7
No-Load Loss Increase: 60% (Amorphous) ; 235% (Silicon Steel)
AMT Performance under Harmonics
250 KVA Transformer Losses @ ~56% Loading
ERDA Industrial Site Field Tests
3000
2500
SiFe Increase - 387 W
AM Increase - 41 W
698
Losses (W)
2000
155
74
Core Eddy Current
99
1500
Core Hysterisis
311
155
33
1000
99
1671
1553
500
Coil
1084
966
0
Expected AMT
Actual AMT
Expected CRGO
Actual CRGO
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 / i1
in : n-th harmonic current
Magnetic Loss = A f + B dl fm Bn /ρ
(A, B : constant)
Amorphous Metal
Silicon Steel
ρ(resistivity)
~ 130 µΩ-cm
~ 50 µΩ-cm
d (thickness)
~ 20 µm
200 µm
l
1-2
2
m
~ 1.5
~2
n
~2
~2
Property/Exponent
Smaller thickness and higher resistivity coupled with smaller exponent m lead
to lower magnetic loss at higher frequencies in amorphous transformer cores.
Harmonic Impact on Transformer Losses -250 kVA
A.
B.
Harmonic Content (THD~25%)
Harmonics
1
3
5
7
9
11
13
15
17
Content (%)
100
1
20
10
1
9
6
1
5
Transformer Losses without Harmonic Distortion
Loss (W)
Amorphous Metal
Silicon Steel
Hyteresis
99
155
Eddy Current
33
311
Total Core Loss
132
466
Coil Loss
966
1,084
Loading Level (%)
55
58
1,098
1,550
Amorphous Metal
Silicon Steel
Hyteresis
99
155
Eddy Current
74
698
Total Core Loss
173
853
1,553
1,671
55
58
1,726
2,524
Total Transformer Loss
C.
Transformer Losses with Harmonic Distortion of Table A
Loss (W)
Coil Loss
Loading Level (%)
Total Transformer Loss
Harmonic Impact on Transformer Losses
Twofold Effect
CURRENT DISTORTION
• INCREASES WINDNG LOSS
• INDUCES VOLTAGE DISTORTION,
INCREASING NO-LOAD LOSS
VOLTAGE DISTORTION
• INCREASES NO-LOAD LOSS
• DECREASES POWER FACTOR
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
Solution to THD Problems
using Amorphous Metal-based Transformers
• 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
“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.