An enterprise of
Bangladesh Steel & Engineering Corporation

ISO 9001-2008 Certified



North Patenga, Chittagong-4204, Bangladesh.
Telephone: 88-031-2501160; 88-031-2501161
Fax: 88-031-2501162 E-mail: gemcobd@yahoo.com

The Technology for Manufacturing Oil-immersed Distribution Transformers:

GEMCO’s corporate thinking is driven by the commitment to quality. The complete in house manufacturing process helps us to ensure optimum quality of the transformer. We have complete testing facility to test and check all the major raw-materials used in manufacturing transformers. CRGO laminations are cut to achieve minimum magnetic flux distortion. To ensure the best quality of the coils of transformers, best quality winding wires and strips are collected through international tender.

Fabrication section ensures the robustness, quality and fine finish of the tank and radiators of transformers.

 The manufacturing process of Transformers covers the following departments/functions:

  1. Transformer Tank Fabrication
  2. Surface Finishing and Painting
  3. Coil Winding
  4. Core Assembly
  5. Core – Coil Assembly
  6. Active Part (Assembled Core  &Coils) Drying
  7. Tank-up
  8. Testing

 COIL WINDING:

    


Coil winding of two types:

  1. High Voltage Coils: HV coils are components of finished transformer. They are made on HV winding machines.
  • A hollow cylindrical former of predetermined diameter and length is being used as base over which coil is wound.
  • Generally Super Enameled Copper Wire is used as basic raw material.
  • The Coils are made in number of layers.
  • The starting and finishing leads of each coil are terminated on one side of the coil.
  • The leads are properly sleeved and locked at number of points.
  • Oil channel is provided between mid-layers for proper cooling of HT coil.

     2.   Low Voltage Coils:

           Coi lWInding

  •  LV coils are also of the components of transformer. The procedure of making low voltage coil is generally same as that of HV-coils, described earlier.
  • The shape of the basic raw-material is rectangular widely known as copper strip.

 

CORE ASSEMBLY:

        Core Assembly

  • The basic raw-material is COLD ROLLED GRAIN ORIENTED (CRGO) Silicon Electrical Steel Sheet.
  • It is in the form of thin sheets & cut to size as per design.
  • Generally three different shapes of core laminations are used in one assembly.
  • These laminations are assembled in such a manner that there is no air gap between the joints of two consecutive sheets.
  • The entire assembly is done on a frame commonly known as core channel (Yoke beam). These frames being used as clamping unit/units of the core assembly. 

 CORE-COIL ASSEMBLY:

     

  • The components produced in the coil winding and core assembly stage are then taken into core-coil assembly stage.
  • The core assembly is vertically placed with the foot plate touching the ground. The top yoke of the core is removed. The limbs of the core are tightly wrapped with cotton tape and then varnished.
  • Cylinder made out of insulating press board is wrapped on all the three limbs.
  • Low voltage coil is placed on the insulated core limbs.
  • Insulating block of specified thickness and number are placed both at the top and bottom of the low voltage coil.
  • High voltage coils are placed over the low voltage coils.
  • Gap between each section of high voltage coils and low voltage coils including top & bottom clearances is maintained with the help of oil ducts, as per design/drawings.
  • The top yoke is re-assembled. Top core frame including core bolts and tie rods are fixed in position.
  • Primary and secondary windings are connected as per requirements. Phase barrier between HV phases at the top are placed as per requirements.
  • Connections to the tapping switch (if required) are made.
  • Finally the complete active part (Core-Coil Assembly) is placed into the vacuum drying chamber.

 FINAL ASSEMBLY (TANK-UP): 

          The final assembly activities are used to carry out after getting Tanks, Covers, all other related parts and dried up Active Parts. The procedure is as follows:

  • The active part is taken out from the drying chamber and the “Megger Test” is carried out.
  • Only if the Megger value is as per the specification, the active part may be taken for final assembly.
  • The tanks supplied by the fabrication section are brought to the final assembly section duly painted.
  • Fitting like HV insulators, LV bushings, phase plate, conservator with oil level indicator are fitted on the top cover of the tank.
  • Nuts-bolts, long pin, short pin, tap changer fittings, angle bolts etc of dried up Active Part are properly retightened.
  • Active part is then placed inside the tank and properly locked by side clamp.
  • Operating knob of tap changer switch is fitted, wherever required.
  • Top cover is then fitted to seal the tank.
  • Connections of primary and secondary to the terminal bushings are made before the Top Cover bolted with Tank.
  • New, filtered, centrifuged transformer oil is filled in the tank up to the mark indicated on the oil level indicator.
  • The completed transformer then placed for routine test after the oil is cooled.

 TRANSFORMER TANK: 

  • We have a state-of-art-in-house facility for manufacturing transformer tanks.
  • All tanks are made of high quality steel and can withstand vacuum as specified by the international standards and the customer. All welding joints are tested, ensuring 100% leak proof and mechanical strength.

 PAINTING: 

          The entire procedure of painting is done under two stages:

  1. Surface Preparation/Cleaning of tanks, COvers, COnservators etc.:
  • Cleaning of tank is done normally by chipping/grinding.
  • The outside surface of the tank with radiator fitted, Conservator, Top Cover and related parts are shot blasted to achieve a very fine  cleaned surface.

     2.   Painting of tanks:

  • After surface preparation and cleaning the tanks, a coat of oil resistant paint is applied on the internal surface of the tank.
  • The outside surface is painted with a coat of Stoving Enamel Red Oxide primer, termed as prime coat and subsequently with one coat of Stoving Enamel Final (grey), termed as final coat.

     3.   Drying:

  • The painted tanks, top cover, conservator with related parts are placed into the drying chamber where they are kept about 40-45minutes at 120°C.

 FINISHING: 

  •  Fittings and accessories are checked.
  • Transformers are filled with oil upto the required level marking.
  • Loose accessories like earthing terminals, bimetallic connectors, dial type thermometers, name plate, rating plate etc. are also checked for proper fitting.
  • Lugs/hooks for lifting and towing complete unit.
  • Facilities for lifting core and coil assembly.
  • Base designed for platform mounting on poles.
  • First filling of oil shall comply to BS: 148/1972 or latest revision of IEC-60296 standard.
  • Each H.T. bushing shall have bolted type bi-metallic connector suitable for accommodating ACSR/AAC having dia range from 9 to 14.5 mm.
  • Each L.T. bushing shall have bolted type bi-metallic connector suitable for accommodating Copper/ACSR/ AAC of area range 2x95mm2 to 2x120mm2.
  • HT & LT bushings are installed on the top cover of the transformer.
  • Dial type thermometer for oil temperature mounted on the top cover of the tank.
  • Earthing terminal shall be at the bottom corner of the tank.
  • Nameplate with transformer rating and winding diagram made of stainless steel has engraved letters filled with black enamel.
  • The tank, conservator and radiator shall be painted with 2 (two) coats of grey finishing paint on an anti corrosive suitable prime.

 QUALITY: 

  • Our Quality Assurance Plan is guided by the urge to provide uncompromising quality to our valued customers to ensure lasting satisfaction. Each transformer undergoes a prescribed range of the tests as per IEC 60076 standards.

 TESTING:

         


Each and every transformer undergoes routine tests as per IEC 60076 requirements. In accordance with IEC the following tests are carried out on finished Transformer as per sequence:

  • Di-electric strength test of transformer oil.
  • Measurement of Insulation Resistance.
  • High Voltage Test.
  • Induced Over Voltage Test.
  • Ratio Test.
  • Vector Group Test.
  • Measurement of No-Load Loss and Excitation Current.
  • Measurement of Load-Loss and Impedance Voltage.
  • Measurement of Winding Resistance.
  • Temperature Rise Test. 

 WRRANTY: 

New Oil-immersed Transformer Warranty:

The NEW OIL-IMMERSED TRANSFORMER you have purchased is warranted under the provisions of this warranty. For a period of TWELVE MONTHS from the date of delivery, the equipment is guaranteed to operate in accordance with its nameplate when operated under normal load, usage, conditions and with proper care, installation and supervision. The seller shall have no liability for damage resulting from improper installation or operation of the equipment, voltage surges, negligence of others, accidents, natural forces, and operations beyond rated capacities, or misuse.

Any mechanical or electrical parts proving defective under such normal operation and installation will be repaired or replaced at seller’s option, by seller. Under no circumstances is seller responsible for any in/out charges associated with the connection reconnection, disassembly or rigging of the unit being serviced under this warranty. Seller's obligations under this warranty shall not, in any event, exceed the amount of the original purchase price of the equipment. In the event that the costs of the repair or replacement would exceed the original purchase price, the seller's obligations under this warranty shall be satisfied by a return of the purchase price.

The seller shall not be liable for special or consequential damages or for delay in performance of this warranty. Seller shall not be responsible for repairs or replacement made by others without the seller’s consent.

The seller does not warrant that the equipment will meet or comply with the requirements of any safety code or regulation of any state, municipality, or other jurisdiction.

The equipment has been sold based upon purchaser’s independent determination that it is appropriate for purchaser’s intended application. The giving or failure to give any advice or recommendation by seller shall not constitute any warranty or impose any liability upon seller.

The warranties made herein shall be IN LIEU of any other warranty, expressed or implied, including but not limited to any IMPLIED WARRANTY OF MERCHANT-ABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Such implied WARRANTIES OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED.

The seller’s salespersons may have made oral statements about the equipment which has been sold. Such statements do not constitute warranties, shall not be relied upon by the purchaser, and are not part of the agreement for sale. The entire agreement for sale is embodied in this document and any documents attached to it and such documents constitute a final expression of the party’s agreement, and are a complete and exclusive statement of the terms and conditions of the agreement. There are no antecedent or extrinsic representations, warranties or collateral provisions that are not intended to be discharged and nullified by this document.

 

TRANSFORMER REPAIR WARRANTY:

Parts and labor on the TRANSFORMER you have had REPAIRED are warranted under the provisions of this warranty. For a period of TWELVE MONTHS from the date of delivery, the equipment is guaranteed to operate in accordance with its nameplate when operated under normal load, usage, conditions and with proper care, installation and supervision. The provider shall have no liability for damage resulting from improper installation or operation of the equipment, voltage surges, negligence of others, accidents, natural forces, and operations beyond rated capacities, or misuse.

Any mechanical or electrical parts proving defective under such normal operation and installation will be repaired or replaced at provider’s option, by provider. Under no circumstances is seller responsible for any in/out charges associated with the connection reconnection, disassembly or rigging of the unit being serviced under this warranty. Seller's obligations under this warranty shall not, in any event, exceed the amount of the original purchase price of the equipment. In the event that the costs of the repair or replacement would exceed the original purchase price, the seller's obligations under this warranty shall be satisfied by a return of the purchase price.

The provider shall not be liable for special or consequential damages or for delay in performance of this warranty. Provider shall not be responsible for repairs or replacement made by others without the provider’s consent.

The provider does not warrant that the equipment will meet or comply with the requirements of any safety code or regulation of any state, municipality, or other jurisdiction.

The equipment has been repaired based upon purchaser’s independent determination that it is appropriate for purchaser’s intended application. The giving or failure to give any advice or recommendation by provider shall not constitute any warranty or impose any liability upon provider.

The warranties made herein shall be IN LIEU of any other warranty, expressed or implied, including but not limited to any IMPLIED WARRANTY OF MERCHANT-ABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Such implied WARRANTIES OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED.

The provider’s salespersons may have made oral statements about the equipment which has been repaired. Such

statements do not constitute warranties, shall not be relied upon by the purchaser, and are not part of the

agreement for sale. The entire agreement for sale is embodied in this document and any documents attached to it and such documents constitute a final expression of the party’s agreement, and are a complete and exclusive statement of the terms and conditions of the agreement. There are no antecedent or extrinsic representations, warranties or collateral provisions that are not intended to be discharged and nullified by this document.