dr. andreas jansen thyssenkrupp electrical steel

Folie 106.06.2013 Dr. Andreas Jansen, ThyssenKrupp Electrical Steel Page 2
Author
Quality Dept., Application Engineering
06.06.2013 Dr. Andreas Jansen, ThyssenKrupp Electrical Steel Page 3
Introduction
Grain Oriented Electrical Steel (GO) is an indispensable soft magnetic
material for high-efficient power & distribution transformers
© Siemens AG © Siemens AG
Agenda
Introduction to grain oriented electrical steel
Production methods and metallurgical background
Magnetic and technological properties
Development of new production technologies
Summary & Outlook
Use of magnetic cores to guide and amplify magnetic flux (density)
in electrical machines:
Basic (ideal) transformer equations:
Magnetic materials with high permeability µr are needed to increase
flux density inside the magnetic circuit (to avoid large cross sections
and/or large winding numbers)
In AC applications, soft magnetic materials are used because they are
easily magnetized and demagnetized
Magnetic circuits in electrical machines (II)
The properties of the core material (i.e. permeability, specific total loss,
workability, costs) determine the design and efficiency of electrical devices
The area of the hysteresis loop
corresponds to the energy loss
during AC magnetization
important Soft Magnetic Material
What is electrical steel?
Flat (thin) steel with insulation coating
Special crystal structure / texture
0 2 4 6 8
Alloying content in %
Grain oriented and non oriented electrical steel
Non Oriented Electrical Steel Grain Oriented Electrical Steel
3 cm 0.03 cm
anisotropic magnetic properties,
specialized for transformers
o la
n J
Crystal orientation in “Goss Texture”
In conventional grain
oriented products, called
“CGO”, the misorientation
Differences between conventional and high-permeability GO:
GO is characterized by an exceptional high crystal grain size up to some ten
millimeters and a very sharp orientation of its grains in the so called “Goss texture”.
10 mm
Production steps in GO manufacturing
Hot
area
Cold
area
very narrow ranges for the inhibitor elements (S, N, Al, ...)
and auxiliary elements (C, Sn, Bi,...)
control of grain structure
avoidance of too strong premature inhibition drop secondary recrystallization purification from inhibitor elements (dissolution + diffusion)
Steelmaking
Roughing rolling 40...80 mm
Prerolling
Box annealing up to 1,200 ºC
Intermediate annealing
Steel shop and continuous casting
Raw iron from blast furnace (Torpedo ladle)
C, Si, Mn, P, S
Desulphurization
3. Pre-rolling
1. continuous
2. pre-heating
Cold process in GO electrical steel manufacturing
Cold rolling Coil preparation & side trimming Hot strip annealing & pickling
Intermediate annealing (for CGO) Final rolling (for CGO) Decarburization
& MgO-coating
(& Laser domain refinement)
Side trimming & slitting
Generation of Goss Texture
= 10...25 µm
CGO grades
HGO grades
From GO to a transformer
Energy loss in a transformer is separated into no-load loss and load loss. Both
are influenced by transformer design (e.g. stacked cores or wound-core designs),
material selection and operating conditions (working induction, load rate etc.)
The no-load loss (”core loss”, ”iron loss”) strongly depends on the core material
Introduction of Building factor
Windings Transformer
induction at working material core of loss totalnominal
er transformof loss load-no BF
Example calculation for a 100 kVA transformer with a building factor of 20%:
Classification of transformers in loss classes
Efficiency class Eo Do Co Bo Ao
maximum losses 320 W 260 W 210 W 180 W 145 W
Grade PowerCore® C
130-30 105-30 090-27 085-23 075-18 weight
Induction No load loss No load loss No load loss No load loss No load loss kg
1,7 Tesla 266,4 W 226,4 W 193,1 W 179,8 W 157,6 W 185
1,5 Tesla 215,2 W 197,2 W 169,1 W 151,1 W 130,6 W 213,5
1,3 Tesla 180,0 W 168,4 W 142,3 W 127,7 W 110,3 W 241,8
PowerCore® H
The no-load loss of a transformer can be improved by decreasing the magnetic flux density.
But then more core material is needed, so that the transformer weight will be increased
In addition an increase of core material leads to higher needs for winding material and thus
higher load losses, too
Energy efficiency can be strongly influenced by selecting an appropriate GO grade
All efficiency classes according to EN 50464-1 can be met with GO electrical steel
Sources of transformer noise
Sources of transformer noise are various
One contribution is given by the magnetostriction of the GO electrical steel sheets
used as laminations in the transformer core
Final correlation of magnetostriction & transformer noise still not clear
cooling
system
Developments towards lower losses
Potentials for further loss improvements are related to all three loss components:
Smoother surfaces
diameter particlemean
Developments towards lower losses (II)
To obtain HGO with low thickness, a new production technology using
“acquired” inhibitors instead of “inherent” inhibitors is more successful
to be balanced by improved inhibitor strength 0
10
20
30
Particel size (nm)
fr e q u e n c y i n %
particle size distribution
d
d/n
The new HGO-TS production technology
Advantages of Thin Slab Casting & Nitriding
Improved temperature homogeneity of the thin slab in the continuous furnace
Final formation of the inhibitors takes place in the stage before secondary grain growth
Nitriding process is based on diffusion and easy to control also for thinner gauges
HGO-TS enables the production of new HGO grades with improved magnetic properties
Summary & outlook
Grain Oriented Electrical Steel is the soft magnetic material for high-efficient
power and distribution transformers. It significantly contributes to the fact that
transformers are among the electric machines with the highest efficiency.
Advantages of GO Electrical Steel
Good availability with wide range of standard grades
Easy handling, good workability, good cutting and slitting features
Used in all transformer types, in stacked as well as in wound cores
Allows a small building size and light weight of transformers
Possibility to repair transformers easily
Recyclability 100% anytime, everywhere
ThyssenKrupp Electrical Steel is continuously improving GO material properties
and production technology in order to support our customers in building
high-efficient and eco-friendly transformers all over the world.
PowerCore® electrical steel is the base material for the complete electricity supply chain
Non oriented electrical
steel in generators
Grain oriented electrical
steel in transformers
motors, e.g. in industrial drives or
traction drives for electric vehicles
power generation power distribution electricity use
Electricity supply chain

dr. andreas jansen thyssenkrupp electrical steel

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