ABB Industrial Transformers

The largest technology base – worldwide

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ABB Industrial Transformers.Unified power for your success.

Series Reactors for AC Arc FurnacesMost AC steel furnaces will require a series reactorin the primary.

For long-arc steel furnace operation additional reactance isnormally required to stabilize the arc and optimize the operation.A series reactor for this purpose is built into the furnace transformertank itself or supplied separately.

AC Arc Furnace TransformersFurnace transformers for long-arc (steel)and short-arc (ferroalloy) operation.

ABB produces transformers for all furnace applications. A robust designguarantees mechanical strength for steel furnace operation and temperaturecontrol for continuous high loads in ferroalloy operation.

DC Arc Furnace TransformersDC arc furnaces are mainly for steel production.

Transformers for DC furnace operation normally come in a transformer/rectifierpackage. The full package can be manufactured/supplied by ABB.

Rectifier TransformersFor various electrolysis applications like aluminiumand other metals and chlorine.

Rectifier transformers are combined with a diode or thyristorrectifier. The applications range from very large aluminiumelectrolysis to various medium size operations.The transformers may have a built-in orseparate voltage regulation unit.

Large Drives Converter TransformersDrives systems for pumping stations,wind tunnels and traction feeding.

The transformers are combined with a thyristor rectifier forvariable speed drives (VSD) systems or frequency conversion.

ABB AGTransformers

Lohfelder Strasse 19-2153604 Bad HonnefGERMANY

Phone: +49(0)2224/14-0E-mail: info@abb.comInternet: www.abb.com/transformers

Note:We reserve the right to make technical changes or modify the contents of this documentwithout prior notice. With regard to purchase orders, the agreed particulars shall prevail.ABB AG does not accept any responsibility whatsoever for potential errors or possible lackof information in this document.

We reserve all rights in this document and in the subject matter and illustrations containedtherein. Any reproduction, disclosure to third parties or utilization of its contents - in wholeor in parts - is forbidden without prior written consent off ABB AG.

Copyright© 2007 ABBAll rights reserved.

Customized solutions by dedicated people in focused factories.

ExperienceABB Industrial Transformers integrates theexperience of highly dedicated people andtechniques from serveral industrial transformerfactories in various countries. This represents thelargest technology base of its kind – worldwide.

QualityABB Industrial Transformers believesthat Quality is a vital element of the productright from the start; it can never be achievedby checks and controls alone.

Built-in quality procedures are implemented evenbefore the designwork starts, ensuring correctinterpretation of customer requirements. Arc furnacesand electrolysis operations put tough stresses ontransformers. Sophisticated 2D and 3D computer programmes calculatedielectric, thermal and mechanical stresses, and our quality programme enables usto check, verify and measure all our processes. Only first-class sub-suppliers areused. The ultimate goal is to maximize overall quality – which results in highreliability and optimum transformer Life Cycle Cost. Advanced monitoringsystems are also available.

Know-How and Research and DevelopmentABB Industrial Transformers has direct access to all the combined transformerknow-how, technical experience and expertise within the ABB Group.

This represents its current know-how base,achieved through dedicated employees,an excellent IT structure and undisputedleadership in Research and Development.ABB Industrial Transformers is continuouslyenlarging this base and finding solutions forthe future – now.

Partnership & ServiceABB Industrial Transformers designs tailor-made,high-current solutions for all our industrial customers.

We are committed to being a flexible and knowledgeable partnerfor you – worldwide. Together we can analyze individual needsand help to ensure that you will receive the optimal transformersolution to suit your requirements.

ABB Industrial Transformers’ global network provideson-demand customer service and support. Our interpre-tations of dissolved gas analysis have been recorded andsystemized.

Focused FactoriesABB Industrial Transformers now concentratesResearch and Development, engineering, manu-facturing and service for industrial transformersprimarily at two specialized and globally focusedfactories within the ABB group, located atLegnano, Italy and Bad Honnef, Germany.

Large Drives Converter Transformers

ApplicationsFor special applications, such as large pumpingstations, wind tunnels and rolling stock, a transformercombined with a frequency converter will supplythe input for a variable speed system. For fixedrailway feeding stations a conversion from normalgrid frequency to railway frequency takes place ina similar way.

DutyThe duty is much related to type of application.In pumping stations a high loading with limitedvariation over time can be expected, while inother applications there may be a more intermittentduty cycle with load peaks.

DesignDrives transformers are mostly built with twosecondary and two primary windings, allowingfor a 12-pulse rectifier reaction. Such transformersare normally built with a tertiary winding systemconnected to a filter bank to take out harmonicscreated by the converter. Due to the operationcycles of the converters, there are strong require-ments for correct inter-winding impedancerelations and accuracy.

Technical FeaturesRatings: Up to 137 MVA

Secondary voltages: Up to 13,4 kV

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Rectifier Transformers

ApplicationsElectrolysis processes are used for the production of metals, such as aluminium, magnesium,copper and zinc, or chemicals, mainly chlorine. The largest installations are those foraluminium electrolysis with several transformer/rectifier units in parallel operation toachieve the required DC current. In all cases the rectifier can be with diodes or thyristors.

DutyElectrolysis is generally considered to be continuousand stable processes, but with a constant high loadingand current harmonics.

DesignDue to a large variety of applications there areseveral influencing factors to consider:

• Rectifier bridge connection: For medium tohigh DC voltage level.

• Rectifier single-way interphase connection: Forlow DC voltage levels combined with high DCcurrents.

• Thyristor or diode rectifier.

• Voltage range and step voltage.

• Double-decker: HV and LV windings intwo levels and wye and delta connectionto achieve 12-pulse reaction.

• Pulse numbers higher than 12: Requiresadditional phase shifting windings.

• LV winding arrangements: Adapted to minimizewinding hotspots and the influence of harmonics.

• LV bushing arrangement: Adapted to rectifierdesign and to limit structural heating.

Voltage regulationThyristor rectifiers normally require transformervoltage regulation with a no-load-tap-changer(NLTC), if any. For short voltage ranges the NLTCcan be situated in a HV tapped winding.

Diode rectifiers will in comparison have a longerrange and a higher number of smaller voltagesteps in the transformer. A multi-coarse-fine on-load-tap-changer (OLTC) or an OLTC/NLTCcombination is preferred, together with LV-sidesaturable reactors for the voltage fine-tuning. Therequired double-wound or auto connectedregulating transformer can, depending on transportor site limitations, be built into the same tank asthe rectifier transformer or into a separate tank.

Technical featuresUnit ratings: Up to 160 MVA

Secondary voltage: Up to 1500 VAC

Unit process current: Up to over 100 kADC

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ApplicationsIn large long-arc steel furnaces with high arc voltages there will generally be required tointroduce extra reactance in order to stabilize the arc during operation. For this purpose,a linear series reactor will be used. The reactor may bebuilt into the same tank as the furnace transformer,or supplied as a separate unit.

AC Arc Furnace Transformers

ApplicationsElectric arc furnace (EAF) transformersare required for many differentfurnace processes and applications.They are built for:

• Steel furnaces, mainly long arc

• Ladle furnaces

• Ferroalloy furnaces and similarwith short or submerged arc

DutySteel arc furnace transformersoperate under very severe conditionswith regard to frequent overcurrentsand overvoltages generated by short-circuits in the furnace and theoperation of the HV circuit breaker(“furnace breaker”). The loading iscyclic, while in other applicationsthe loading is more continuous athigh utilization.

DesignABB EAF transformers are rigidly designed towithstand repeated short circuit conditions andhigh thermal stresses and to be protected againstoperational overvoltages.

Design options:

• Direct or indirect regulation

• On-load or no-load tap changer (OLTC or NLTC)

• Built-in reactor for long-arc stability

• Secondary bushing arrangements and designs,air or water cooled

• Internal secondary phaseclosure (internaldelta)

• RC-SA high voltageprotection system

Series Reactors

DutyFor operational flexibility the reactor will normallybe supplied with a tap changer. Depending on themelting process and type of steel being producedthis may be an on-load or no-load tap changerwith the required number of steps.

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Direct RegulationThe secondary voltage can be regulated bytapping the primary winding. Step voltages overthe range will be unequal, due to the inherentwinding design, but adaptations can be madeto satisfy most requirements. A single core-coilunit makes this the most cost-effective regulationprinciple in a furnace transformer as long as a

suitable on-loadtap changer isavailable.A primary star-delta reconnectionswitch will expandthe range.

Indirect RegulationWhen equal and/or very smallvoltage steps or a very longregulating range is required,the alternative will be thebooster regulation with twocore-coil units directlyconnected in the same tank. The main unit will supply a fixedLV component and the series unit will supply a variable andreversible LV component. The two LV systems are connectedin series for the desired LV voltage positions and range.

Over-voltage ProtectionIn order to protect the HV side of the transformer from incomingswitching over-voltages, a system of RC filters and surge arresters(SA) should be fitted to the HV side of the transformer. On theLV side capacitors may be added to suppress over-voltages fromthe arc.

Technical FeaturesRatings: Up to 200 MVASecondary voltages: Up to 1500 VElectrode current (steel): Up to 100 kAElectrode current (Fe-alloy): Up to 160 kA

DesignThe reactor will have the same heavyduty as the furnace transformer itself.Therefore the design has to be veryrugged in order to maintain stabilityand linearity of the reactance. The ABBreactors for this kind of application arebuilt as coreless coils surrounded by ashielding structure of core laminationsin a 3-phase arrangement.

Technical FeaturesRatings: Up to 60 MVAr

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DC Arc Furnace Transformers

ApplicationsMost large DC arc furnaces are built for steelproduction. The use of a thyristor rectifier forthe conversion to DC will normally reduce therequirement for on-load voltage regulation ofthe furnace transformer. The step voltages will belarger than for an AC furnace transformer and ano-load tap changer (NLTC) will in many applicationsbe adequate.

DutyBeing a rectifier transformer for furnace operation,the DC furnace transformer will have to withstandthe characteristic stresses of furnace operation, aswell as the additional stresses related to rectifieroperation, including generated current harmonics.Also, the HV side needs to be protected fromfrequent switching overvoltages.

DesignDC furnace transformers are mostly built withtwo axially displaced LV windings, normallyone connected in delta and one in wye, eachhaving a separate high voltage winding. In thisdouble-decker design thetransformer is connected totwo six-pulse rectifiers, addingup to a 12-pulse system ortwo parallel 6-pulse systems.The regulation of the LVtransformer voltage is normallydone by using a NLTC in theprimary winding.The location of the 6-pulserectifiers can be on the sameside of the transformer or onopposite sides, as requiredby plant layout.

Intermediate yokeDC furnace transformers in double-decker design,having two HV-LV voltage systems on the samecore may have an intermediate yoke to enablelargely independent operation of the two systems.

Technical FeaturesRatings: Up to 120 MVA

Secondary voltages: Up to 1200 V

Electrode current: Up to over 100 kADC