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8/3/2019 ALUMINIUM vs COPPER_Cost & Characteristics Comparison_20100315
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© ABB GroupApril 5, 2010 | Slide 1
Aluminum vs. CopperVacuum Cast Coil Transformers forLonza 2.5
March 2010, PPTR, Chang-Hyeon Lee
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© ABB GroupApril 5, 2010 | Slide 2
Introduction (1)
During the 2nd World War, Copper became scarce andmanufacturers started using Al as an alternative conductor forelectrical transmission and distribution.
For transformers, up to the last 30 years, there were notmany suppliers of Al strips, thin foils or wires as conductors
Only LV windings were made in Aluminum
There were not many manufacturers of special HV foilwinding machineries
So everybody was using Copper on HV windings
Because they had no other options…
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© ABB GroupApril 5, 2010 | Slide 3
Introduction (2)
… the option appeared
There were several reasons that led the changes
Aluminum is the second most plentiful metallic element on the Earth,so no problems with supply
Second lowest density
High corrosion resistance thanks to its Alumina protection
High electrical and thermal conductivity
Higher conductivity than copper, weight for weight
And it is cheap & light with stable price, which is also interesting!
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© ABB GroupApril 5, 2010 | Slide 4
Comparing Aluminum & Copper (1)Common reasons for winding material choice :
FalseTrueCommon reasons for choice of winding material
XAluminum-wound transformer terminations are incompatible with
copper line and load cables.
XProperly terminating line and load connections is more difficult for
aluminum-wound transformers.
XLine and load connections to copper-wound transformers are more
reliable than those of aluminum-wound transformers
XCopper-wound transformers can be made with smaller size than
aluminum-wound equivalents.
XAluminum-wound transformers have higher hot-spot temperaturesbecause copper is a better thermal conductor than aluminum.
XAluminum-wound transformers have higher losses because copper
is a better conductor.
XAluminum-wound transformers are lighter in weight than theircopper-wound equivalents as well as cheaper price
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© ABB GroupApril 5, 2010 | Slide 5
Comparing Aluminum & Copper (2)Physical properties of two conductors in general
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© ABB GroupApril 5, 2010 | Slide 6
Comparing Aluminum & Copper (3)Coefficient of thermal expansion
Coefficient of expansion of Aluminum : 23.1
Coefficient of expansion of Copper : 16.5
Aluminum expands one third more than copper
Some says it creates problems with bolted connections
But, using proper hardware aluminum joints are equalto copper joints
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© ABB GroupApril 5, 2010 | Slide 7
Comparing Aluminum & Copper (4)Electrical conductivity
Aluminum (σAl) : 37.8 x 106 Ω-1m-1
Copper (σCu) : 59.6 x 106 Ω-1m-1
Aluminum has only 61% of conductivity against copper, sohigher losses?
For two identical transformers (same winding
resistance and length , amps/turns), the conductorcross-section will be inversed to the electricalconductivity. The cross-section on Al conductor will be1.6 times against copper,
Sal
/Scu
= σCu
/ σAl
=59.6/37.8 = 1.6 Sal
= 1.6Scu
With the increase of cross-section, the result in energylosses are the same
Comparing the cost of both materials, lower losses will
be cheaper on Aluminum
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© ABB GroupApril 5, 2010 | Slide 8
Comparison of Transformer (Al vs Cu)General specification to be compared
General specification of transformer (same on both Cu & Al TRs)
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© ABB GroupApril 5, 2010 | Slide 9
Comparison of Transformer (Al vs. Cu)Electrical characteristics and dimension
Characteristics & Price comparison on 1600kVA transformers
All electrical and dielectric characteristics are the nearly same on bothCu and Al transformers
Price comparison except accessories 100% 75~77%
Price comparison is based on material costs dated on Mar. 15, 2010. It may be changed according tocommodity price variation.
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© ABB GroupApril 5, 2010 | Slide 10
Thermal ability to withstand to short-circuitRequirements according to IEC 60076-5 (2006)
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© ABB GroupApril 5, 2010 | Slide 11
Thermal ability to withstand to short-circuitWinding temperature calculation while short-circuit
200200350350Max. permissible Avg. winding temp
162183161191Highest Avg. winding temperature
LVHVLVHV
AluminumAluminumCopperCopper
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© ABB GroupApril 5, 2010 | Slide 12
Ability to withstand the dynamic effects of short circuit
High reliability on the coil structures
Robust mechanical coil structure thanks to encapsulation ofconductor material in solid insulation
Ability to withstand the dynamic effects of short circuit shall bedemonstrated either
by tests, or
by calculation and design and manufacture considerations
The reference list for type tests including dynamic short-circuittest is enclosed on next slide
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© ABB GroupApril 5, 2010 | Slide 13
Ability to withstand the dynamic effects of short circuitType & Special Test List (conducted by authorized third parties)
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© ABB GroupApril 5, 2010 | Slide 14
Comparison of VCC Transformer (Al vs. Cu)General comparison
Cost (Initial investment)Cost (Initial investment)
Dimension & WeightDimension & Weight
Overload CapacityOverload Capacity
Dielectric StrengthDielectric Strength
Short Circuit CapabilityShort Circuit CapabilityElectrical CharacteristicsElectrical Characteristics
AluminumAluminumCopperCopper
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© ABB GroupApril 5, 2010 | Slide 15
Comparison of Transformer (Al vs. Cu)Advantages on Al transformers
Less initial investment costs even if the operational running costsare the same (approx. 25% less expensive)
Same life cycle expectation because transformers are run at
equivalent operating temperatures, the insulation systems age atthe same rate for each design, it means that longer life cycle on ALtransformer on the same price
Lower operational running costs due to higher efficiency based on
the same price Thermal expansion of Al and epoxy resin is more similar, so
thermal stresses are kept to the minimum
Major VCC transformer manufacturers apply Aluminum VCC as
their standard products
ABB, Siemens, Areva, ….
Aluminum VCC is a standard product in Americas, Europe, Asiaand so on
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© ABB GroupApril 5, 2010 | Slide 16
Comparing Aluminum & Copperin terms of transformer characteristics
Copper Aluminium
Efficiency & Losses according to customer's request according to customer's request
Weight (%) Heavy (100)Lighter (85)
Easy for handling and transportion
Small (100) a little bigger (105)
%Impedance
Regulation
Ratio
Dielectric characteristics
Temperature rise
Thermal ability to withstand
short-circuit
Ability to withstand the
dynamic effects of short-
circuit
Mechnical Strength
Al and Cu conductor transformers have different criteria for maximum permissible
values of the average temperature of winding after short-circuit, so both different types of
transformers can comply with international standards.
It depends on properties of the maximum permissible temperatures on the soild
insulation system,so both kinds of transformers can comply with the requirement.
No relation with conductor material (depending on %IZ and Loss )
It depends on properties of expoxy system with mechanical reinforcement, so both kinds
of transformers can comply with the requirement.
No relation with conductor material
The dynamic effects can be demonstrated either by tests or calculations & design
considerations, so both different types of transformers can comply with international
standards. The transformers have much stronger ability to withstand while short-
circuiting because the windings are encapsulated in the soild insulation system.
No relation with conductor material
No relation with conductor material (depending on turns and geometric )
In case of the same kVA, it needs more AL(sqmm) than CU to reduce the current density
due to different conductivity. So the size of AL transforemr is a little bit bigger(1.05~1.1)
than CU transformer depending on the kVA, primary voltage and impedance.
Size of Tr (%)
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© ABB GroupApril 5, 2010 | Slide 17