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Power Transformers

HYUNDAI,A RELIABLEBUSINESS PARTNERIN THE POWERINDUSTRYCONTENTS06Production Range07Transformer Design08Core Construction10Winding12Core & Coil Assembling14Tank15Cooling System16Testing17Research & Development17Quality Assurance18Worldwide Experiences

Power TransformersUsing cutting-edge designs, state-of-the-art manufacturingfacilities, and innovative production technology, we manufacturehigh-quality power and distribution transformers with a ratedvoltage of up to 800 kV and a capacity of up to 1,500 MVA.Hyundai transformers are in service around the world and meetinternational standards such as IEC, ANSI, NEMA, CSA, AS, and ES.

ULSAN FACTORY, KOREAALABAMA FACTORYHYUNDAI POWER TRANSFORMERS USA, INC.SOFIA FACTORYHYUNDAI ELECTRIC - BULGARIA

HyundaiTransformersat a GlanceHyundai Electric, being specialized in designand manufacturing of electrical equipment,has been pursuing the business goal ofproviding total solution to the customersaround the world since its establishment.We are offering the complete range ofelectrical equipment for power plants,transmission and distribution, and variousindustrial sectors such as Transformers, SF6Gas Insulated Switchgear, Medium VoltageSwitchgear, Motors, Generators, IntegratedControl & Monitoring Systems, PowerElectronics, etc.Among such wide range of products, HyundaiTransformers, featuring excellent performanceand a high level of reliability proven througha lot of experiences accumulated over a longspan of period, have been delivered to thecustomers and gained good reputation fromthe customers.To best serve our clients with global capacity,we are currently operating Ulsan plant inKorea, Alabama plant in the USA and Sofiaplant in Bulgaria.Hyundai Ulsan factory, equipped with themost advanced manufacturing and testingequipment, and having the annual capacityof 120,000 MVA, is manufacturing the wholerange of transformers from distribution andpower transformers up to 800 kV includingcast resin and various kinds of special purposetransformers such as furnace transformersand gas transformers, etc.Hyundai Power Transformer USA inMontgomery, Alabama is built based onthe invaluable experience and cutting-edgetechnologies gained over 30 years. HyundaiPower Transformer USA strictly follows theprocedures that have been tested and provenfrom Ulsan plant in order to guarantee theproduction of high-quality power transformers.The new plant is fully capable of providingclient-specific power transformers to mostly,but not limited to, North America, SouthAmerica, and African regions. Always strivingto produce innovative and superior powertransformers, Hyundai Power TransformerUSA is confident in achieving worldwidecustomer satisfaction.And Hyundai Sofia factory, with its longexperience of more than 50 years inmanufacturing transformer and tap changers,has been supplying its products to thecustomers for power generation, transmissionand distribution areas.Hyundai, having the competitive edges in price,delivery and quality, has become the worldleading supplier of transformers over the shortspan of period since its establishment. Weare committed to offer the best service for thecustomers including after-sales service.Hyundai has kept total quality system certifiedby ISO 9001 and we are providing qualityproducts and services for the customers inaccordance with their requirements.

06 Power TransformersProduction RangeBeing classified by its application, construction and ratings,Production range of Hyundai Transformer fully covers abovetransformers can be divided into Power Transformer,mentioned transformers and services as follows ;Distribution Transformer, Reactor, Cast Resin Transformerand Special Transformer.Transformer PlantScope of Production & ServicesUlsan Factory in Korea- Power Transformer up to 800 kV / 1,500 MVA- Distribution Transformer- Cast Resin Transformer- Dry Type Transformer- Reactor- Special TransformerAlabama Factory in USA- Power Transformer up to 500 kV / 600 MVA- Distribution Transformer- Reactor- Special TransformerSofia Factory in Bulgaria- Power Transformer up to 420 kV / 200 MVA- Distribution Transformer- Instrument Transformer up to 145 kV- Special Transformer- Tap Changers such as On-Load Tap Changer,Off-circuit Tap Changer and SF6 Gas Insulated Tap ChangerServices to be provided bytransformer factory- Supervision of Transformer Installation & Commissioning- Advisory Services of Transformer Specification- Training of Customer Personnel- Inspection & Trouble Shooting Service- Investigation and Assessment of ProblemsPower TransformerReactorCast Resin TransformerTap Changer

Hyundai Electric 07Transformer DesignBy utilizing the most modern and up-to-date designTaking into account of any possible case of short-circuittechnology, Hyundai provides designs which can meet thefault which may be incurred in service, we utilize acustomer's various requirements and international orcomputer program to calculate accurate radial force, axialnational standards of IEC, ANSI, NEMA, CSA, BS, AS, etc.force and spacer of winding.Also Hyundai design team has sufficient experiences andParticularly, Hyundai can perform seismic analysis with theproven records which can meet the customer's variouscomputer program to ensure that the transformer has theneeds of power, voltage, mode of operation, low noisecapability to withstand the seismic condition.level, connection techniques, type of cooling, transport andinstallation.

08 Power TransformersCore ConstructionThe cores for Hyundai transformers are made of highIn the core of large power transformer, suitable insulationquality, cold-rolled, grain-oriented silicon steel coated withpapers are inserted between the laminations for themagnesium-silicate-phosphate.purpose of reducing eddy currents and also to minimizeLaser scribed or plasma treated silicon steel can be usedmagnetic short-circuit.for those require low loss design.And for the effective cooling, cooling ducts are providedThe standard core construction type of Hyundai transformerbetween the core laminations.is ‘core form type’ having three leg core or five leg core ofthree phase and two leg core, three leg core or four legThe leg core where the hard wooden bars are inserted, arecore of single phase according to the customer’s specialtightened with synthetic resin impregnated glass band.requirement.Step Lap Core LaminationStep lap core lamination is used to reduce no load losses and noise level.

Hyundai Electric 09Core Cut-to-length MachineThe oriented silicon steel is cut by computerizedmachine to minimize air gap in the joint duringassembly.Core StackingFive Leg Core stackingCore Erection EquipmentSpecial core erection equipment is used for thelarge core in order to prevent deflection fromstress and strain during upright setting of thecores.

10 Power TransformersWindingThe winding is made of copper conductor covered withseveral layers of insulation paper or enamel coating ofhigh dielectric strength. Rectangular conductor, multipleconductor and transposed conductor are employed in thewinding. The most optimized conductor is selected afterconsidering the voltage and capacity of the transformer.Especially, the transposed conductor is composed ofseveral wires individually covered with enamel and thisContinuously Transposed Conductorentire wire unit is covered with several layers of insulationpaper.The advantage of using transposed conductor is to decreaseAnd during the manufacturing process of windings, theeddy current loss in the windings, improve of the laminationfollowing factors are taken into account ;factor and manufacture windings within a short time span. Short circuitWhen manufacturing large power transformers, the most Ability to withstand impulsessuitable winding method is employed according to the Eddy current losscapacity, voltage and tap range of each transformer. Ability to distribute over-voltageHorizontal Winding MachineVertical Winding Machine

Hyundai Electric 11Layer WindingHelical WindingApplied to low voltage and large current windingsEmployed according to the magnitude of current in case of low voltagewindingDisc WindingInterleaved Layer WindingApplied for high voltage winding and classified into continuous andinterleaved disc windingApplied for tap winding

12 Power TransformersCore & Coil AssemblingFor insulation, all Hyundai transformers have a concentricThe bottom of the windings rest on the supporting systemwinding structure. One or more insulating cylinders areof the lower yoke. And a large wooden press ring calledplaced around the core legs. The number of insulating"pressing wood" is provided at the top of windings.cylinder depends on the voltage stress between the leg andThe windings are pressed by means of the pressing woodthe winding itself.and bolts on the upper clamp device. All leads and busbarare tightly supported to withstand short-circuit force.Vertical spacers are provided to produce an oil duct forthe cooling of windings. Between the low and high voltageAfter the core and coil assembly is completed, it will bewinding a number of insulating cylinders are provided atdried in the vapor phase drying plants under high vacuumfixed distance from each other by using vertical spacers.condition for the purpose of eliminating moisture content.The high voltage winding is wound on the outer cylinder.Transformer under In-tanking ProcessOn completion of the vacuum drying, the core and coil assembly is inserted in the tank.

Hyundai Electric 13Winding InsertingLow voltage winding, high voltage winding and tapwinding are inserted into a leg core.Core and Coil AssemblyCore and coil assembly of the transformer will putthe core, windings clamping device, tap changerand lead together.Vapor Phase Drying PlantVacuum drying with heat in vapor phase dryingplants.

14 Power TransformersTankProtection of the active parts in the transformer is veryHyundai's strict welding procedure and leak test standardimportant, especially in case of high voltage and largeassure 100% leakproof seams and maximum mechanicalcurrent transformer.strength.While achieving the optimized size of transformer to suit theAfter finishing the welding work, it is shot-blasted tosite condition for installation, the main role of the tank isremove all dust and spatters before painting.to protect the active parts and the tank is manufactured tohave sufficient strength to withstand internal and externalfaults that may occur during operation.And the various ancillary devices such as lifting lug, jackpad, pulling eye and skid base are designed and providedon the tank so that the transformer can be moved in anydirection without damage when using rollers, plates orrails.Non-Destructive Test on Transformer TankPainting of TankTransformer TankThe tank is painted with HHI standard painting system which is polyurethane resin in order to prevent the tank from any possible corrosionwhich may appear according to the site condition.The tank is made of high quality mild steel.

Hyundai Electric 15Cooling SystemA transformer in service has losses which are transformedin to heat to be dissipated but causing to a temperature risein the transformer. In order not to allow the temperature torise above the permissible level, a suitable cooling methodshould be considered and adopted.Generally, the suitable cooling method for the transformeris determined by the customer after due considerationof transformer capacity and the circumstances at theinstallation site.Hyundai can design and manufacture transformerwith various types of cooling systems according to thecustomer’s requirement. ONAN: Natural oil cooling (ON), Natural air cooling (AN) ONAF: Natural oil cooling (ON), Forced air cooling (AF) OFAF: Forced oil cooling (OF), Forced air cooling (AF) ODAF: Directed oil cooling (OD), Forced air cooling (AF)Oil to Air Cooler OFWF: Forced oil cooling (OF), Forced water cooling (WF)Panel Type RadiatorOil to Water Cooler