WIRES AND TRANSPOSED CABLES IN TRANSFORMERS

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

06.06.2013 Dr. Stefan Beckmöller, Essex Germany GmbH Page 2

Continuous Transposed Cables

Energy Efficient Transformers

CTC

Continuous Transposed Cable

Source: Siemens AG


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


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


Requirement to wires in Transformer

Conductivity

Mechanic strength

Chemical strength

Lifetime

Windability

Electric strength

Conductor

Varnish-insulation

Construction

Cable-insulation

Process


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


Cable-insulation

Conductor

Varnish-insulation

Construction

Process


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


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

10 06.06.2013 Dr. Stefan Beckmöller, Essex Germany GmbH Page 10

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


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


Conductor: Material

Source: Aurubis

Copper Rod Production

Metallurgy Electrolyse Continuous Rod Casting

Up-Cast Verfahren

Source: Aurubis


Drawing Rolling

Rectangular Wire Production

Conductor: Material

Pre-material


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


Cable-insulation

Conductor

Varnish-insulation

Construction

Process


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



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


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



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


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


Cable-insulation

Conductor

Varnish-insulation

Construction

Process


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



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


CTC with improved cooling (low voltage winding)


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


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


Cable-insulation

Conductor

Varnish-insulation

Construction

Process


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


b

Sf

RR


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




the crank length increases with the

width of the strand

CTC with a high ratio width /

height incline to tilt

b

c


the radial size is depended from

ratio pitch / crank length

Small transposing factors

increases the radial size

SR/c

HR


Cable-insulation

Conductor

Varnish-insulation

Construction

Process


CTC Production Process

Pay off Transposing

head

Paper Wrapping Caterpillar Winder


Work principle

Counter holder*

Stack pusher

Strand pusher

Production

Rotation

CTC Production Process


Test and specification


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


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


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


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


Thank you very much

for your attention


Documents

WIRES AND TRANSPOSED CABLES IN TRANSFORMERS