wires and transposed cables in transformers
TRANSCRIPT
TRANSFORM Partner
Dr. Stefan Beckmöller
ESSEX Germany GmbH
WIRES AND TRANSPOSED CABLES IN TRANSFORMERS
Dr. Stefan Beckmöller
Studies at University
„Metallurgy with focus metal forming“ at RWTH Aachen
PhD at RWTH Aachen
Professional Carreer
Quality Engineer at Kabelwerke Rheydt
Project Engineer at Lackdraht Union GmbH, Arolsen
Head of R&D Lacroix & Kress GmbH, Bramsche
Head of R&D Essex Germany GmbH, Arolsen
Vita
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Continuous Transposed Cables
Energy Efficient Transformers
CTC
Continuous Transposed Cable
Source: Siemens AG
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A brief history
1912 Ludwig Roebel invents single insulated and
transposed strands to replace the large
cross-section conductors that were currently
in use within generator designs
Since 1940 Transformer designs using the idea of
Ludwig Roebel
new challenges relating to efficiency, profitability and
environmental compatibility
CTC requirements
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Why do we use CTC?
high flexibility
length
compensation
Fast and efficient
winding of the active
part of the
power transformer
due to transposition.
Reduced impact of
magnetic field by
increased surface due
to single isolated strips
and transposition.
(skin + proximity effect)
B
E
S i
S I e1
A1
e2
A2
reduced electrical
losses
improved cooling
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Requirement to wires in Transformer
Conductivity
Mechanic strength
Chemical strength
Lifetime
Windability
Electric strength
Conductor
Varnish-insulation
Construction
Cable-insulation
Process
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CTC construction
CTC – build up Properties influenced by
Insulation
Construction
Reel-type
Bond Coat
Co
st
pre
ss
ure
Process
Bond Coat
Conductor
Insulation
Process
Reel-type
Construction
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Cable-insulation
Conductor
Varnish-insulation
Construction
Process
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Conductor: Material
Soft
Hard
Copper Cu-ETP1
Cu-OF1
E.g. CPR1, CPR2, CPR3
Hard Copper alloys CuAg 0,03
CuAg 0,10
Aluminium + low cost
- low conductivity and stiffness
Conductor
Rod
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Copper Aluminium
Aspect red-orange metallic
% of geosphere 0,01 % 7,75 %
Density 8,92 g/m³ 2,70 g/m³
Melting point 1083 ºC 658 ºC
Linear heat expansion 17,0 x 10-6 1/K 23,5 x 10-6 1/K
Young-modulus 13,0 x 104 MPa 7,1 x 104 MPa
Thermal conductivity 385 W/mK 230 W/mK
Electric conductivity > 58,58 m/(Ω mm²) > 35,67 m/(Ω mm²)
Price (15.04.2013) 5,741 € / kg 1,416 € / kg
General remarks
↑ welding
↑ forming
low oxidation rate
↓ welding
high oxidation rate
↓ bending
↓ plastic flow
CCA* (15 %)
Bi-Metall
---
3,63 g/m³
658 ºC
240 W/mK
> 37,35 m/(Ωmm²)*
metall+forming
↑ welding
↓ recycling
↓ bending
* ↑ = copper @ 5 MHz
Conductor: Material
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Electric Conductivity
3 0
3 5
4 0
4 5
50
55
6 0
0 ,0 0 0 ,0 2 0 ,0 4 0 ,0 6 0 ,0 8 0 ,10 0 ,12
mixture in mass-%
ele
ctr
ic c
on
du
cti
vit
y [
m/O
mm
²]
P
CdAg, Zn
Sn
AL
Mn
Co
Fe
source: DKI
Conductor: Material
Conductivity Copper > 58,58
pure Copper ≈ 60
Silver ≈ 62
Aluminium ≈ 36
Impurities reduces conductivity
Silver has less impact to conductivity
Hardening reduces conductivity
Cu-ETP1 and Cu-OFE 99,99 %
copper content
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Mechanical strength
OF-Cu
source: DKI
OF-Cu Ag
Conductor: Material
creep behavior of materials after
1.000 h
material begins to anneal with
temperature
impurity silver enhances
mechanical behavior without
dramatic impact to the
conductivity
Typical alloy CuAg0,03 and
CuAg0,10
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Conductor: Material
Source: Aurubis
Copper Rod Production
Metallurgy Electrolyse Continuous Rod Casting
Up-Cast Verfahren
Source: Aurubis
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Drawing Rolling
Rectangular Wire Production
Conductor: Material
Pre-material
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Advantage
• Direct production from rod to square size
• No annealing necessary
• Clean surface of the pressed material (no fat, flaks, …)
• Set up times low
• Flexible in dimension and shape
• No emulsion necessary
Disadvantage
• “Slow” production process
• Sensitive to cleanness off pre-material
• Soft material sensitive to scratches and oxidation
• Increased copper scrap
Conform Technology
Conductor: Material
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Cable-insulation
Conductor
Varnish-insulation
Construction
Process
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Varnish insulation: Material
Excellent adhesion, flexibility and oil resistance Polyvinylacetal
Increased heat resistance
Comparable with impregnation varnishes
Polyesterimid +
Polyamidimid
Epoxy-
Bond coat
Concentric Standard
Partial Improved
Specials PET- foil, Aramid- paper,
Prepreg, glass yarn, …
strand
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Varnish insulation: Material
Electric Insulation
today 90 % PVA - class 120
break down voltage > 50 V/µm
reduced contact failure
insulation resistance > 500 M km
better workability
higher temperature class
higher abrasion withstand
higher bond strength
Insulation types
Introduction of isolation types
Polyimid 1958
Polyesterimid 1962
Polyester 1955
Polyurethane 1950
Polyvinylacetal 1938
Polyamidimid 1964
240°C
120°C
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Varnish Insulation: possible solutions
Polyvinylacetal
Temperature-index
120 ºC
Heat shock
155 ºC
Resoftening temp.
> 215 ºC
soldering
no
Chem. Resistance
very good
Polyurethan
Temperature-index
180 ºC
Heat shock
200 ºC
Resoftening temp.
> 250 ºC
Soldering
yes
Chem. Resistance
good
T. Poly. (imid)
Polyamidimid +
Temperature-index
200 ºC
Heat shock
220 ºC
Resoftening temp.
> 340 ºC
soldering
no
Chem. Resistance
good
Polyamidimid
Temperature-index
220 ºC
Heat shock
240 ºC
Resoftening temp.
> 400 ºC
soldering
no
Chem. Resistance
very good
Polyimid
Temperature-index
240 ºC
Heat shock
260 ºC
Resoftening temp.
> 500 ºC
soldering
no
Chem. Resistance
very good
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Varnish insulation: Material
Bond Coat (Epoxy)
increased strength at working
condition (5 x stiffness @ 120 °C)
compatibility with transformer oil
hardening during drying process
(start @ 90 °C depending on type
in hot air or vapour phase)
different application possible:
all around radial bond
simple usage
shelf life min. 6 month depending
bond type and climate
Mechanical strength
(bond coat)
0
1000
2000
3000
4000
5000
6000
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0
Bending [mm]
Fo
rce [
N]
bonded
not bonded
26,6
24,8
12,5
7,86,4
0
5
10
15
20
25
30
Sti
ffn
ess f
acto
r
20°C 60°C 80°C 105°C 120°C
Temperatur
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Varnish insulation: Application
Process
Source MAG
~ 2
6 m
Product
Isolation increase:
~ 0,10 mm
10 layers with 0,005 mm
thickness
Bdv > 2 kV
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Cable-insulation
Conductor
Varnish-insulation
Construction
Process
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Cable insulation: Material
High thermal resistance, high mechanic strength,
Resistance against oil, Aramid
Specials Glass yarn, …
Cellulose But to but wrapping smooth
staggering Micro crepe
Protection
paper * Without wrapping Without inter column separator
Aramid Perforated* Gap
PET Filament Cordex *
Aramid Diamond*
Continuous
Transposed Cable
* Essex Patente
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Cable insulation: Material
Electric Insulation advantage:
- thick insulation
- dielectric strength
in oil
different types:
- Cellulose
- Aramid
disadvantage:
- cooling behavior
- thermal aging
Paper types for electric insulation
Papertype Remarks
Kraft- Paper 5A2-1H1, paper with high purity
Kraft- Paper, calendared 5A4-1M2, high density and break down voltage
Thermo stabilized 5A2-1M1, increased thermal resistance
Thermo stabilized, calendared
5A4-1M2, high density and break down voltage, increased thermal resistance
Thermo stabilized, calendared, crepe
Paper with high mechanical strength, used for outer layers
Epoxy coated, Thermo stabilized
Bondable outer layers
Aramid High thermal resistance, used for traction transformers
Epoxy coated Aramid Bondable outer layers for traction transformers
Transformer- Pressboard P 2.1, inter column separator
Glass woven fabric Winding used for resin cast transformers
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CTC with improved cooling (low voltage winding)
Cable insulation: Material
perforated Cordex diamond Paperless CTC
Electric Insulation
for low voltage
winding with
increased heat
transfer
increased filling
factor
reduced cooling
higher efficiency
in power transformers
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Typical paper set up for CTC
2 outer layers, 50 % staggering
inner layers but to but, ~ 30 % shifted
Cable insulation: Process
Paper wrapping process
application of inner layers
outer layer
inner layer
CTC
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Cable-insulation
Conductor
Varnish-insulation
Construction
Process
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Cable insulation: Construction
pitch n
dSR
Transposing factor
d = Winding diameter
n = number of strands
b = width of conductor
c = crank length Eb
n
2
1Intercolumn Paper I = (min. 8 mm)
ZEan
2
1Radial Size HR = (odd numbers)
ZEan
2
2Radial Size HR = (even numbers)
ZEb I 2Axial Size BA =
I
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b
Sf
RR
Cable insulation: Construction
Limits of Transposed Cable
Dimension range of strands in CTC
3,10 12,50
3,15
1,00
0,00
0,50
1,00
1,50
2,00
2,50
3,00
3,50
1,00 3,00 5,00 7,00 9,00 11,00 13,00
width [mm]
thic
kn
es
s [m
m]
3,5 … 39 mm²
Transposition head
Radial size mm < 79
Axial size mm < 26
Crank length mm 15 - 50
Geometry
Transposing factor > 5
ratio width/thickness < 8
Other dimension on request possible
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Cable insulation: Construction
Limits of Transposed Cable
the crank length increases with the
width of the strand
CTC with a high ratio width /
height incline to tilt
b
c
Limits of Transposed Cable
the radial size is depended from
ratio pitch / crank length
Small transposing factors
increases the radial size
SR/c
HR
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Cable-insulation
Conductor
Varnish-insulation
Construction
Process
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CTC Production Process
Pay off Transposing
head
Paper Wrapping Caterpillar Winder
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Work principle
Counter holder*
Stack pusher
Strand pusher
Production
Rotation
CTC Production Process
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Test and specification
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Tests and specification
specification
Copper DIN 1977
Aluminium DIN EN 573-3
Rectangular magnet wire – general requirements IEC 60317-0-2
Magnet wire – specific requirements IEC 60317-..
Magnet wire – test method IEC 60851-..
Magnet wire – temperature index IEC 60172
Cellulosic paper IEC 60554
Aramid - Paper IEC 60819
Pressboard IEC 60641
Drums and spools DIN 46391/1, IEC 60264
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Product test
Yield strength
tan delta
Snap test
Abrasion
El. Resistance
Adhesion Break Down
Voltage
Heat Shock
Oil Compatibility
Staggering;
bulging
Spring Back
Elongation Bonding
Softening
Temperature Test depending to magnet wire
Sizes
Shorts in CTC
CTC
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Summary
Continuous Transposed Cable look simple but are a “high tech”
product
Continuous Transposed Cable are a customized product
A lot of things are possible with a close work together of the CTC
producer and the transformer producer
If the others belief, you're at the end,
now you really have to start.
Konrad Adenauer
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Superior Essex
23 plants in 9 countries
in
America, Europe and Asia
Cable for telecomunication
Round and flat enameled wires out of
copper and aluminium
Covered products
Continuous Transposed Cables
Isolation varnishes
Copper – Rod
Member of the LS-Cable Group
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Thank you very much
for your attention
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