Manufacturing Facilities:

TVL is located at Savar, a clean & green environment. There are separate shops for Design, Core slitting, Cutting, annealing, coil winding, Core coil assembly, Tanking & painting, Testing. The shop floor is highly adequate with material handling facilities and has a liberal floor area for work.

Design & Engineering:

TVL has a group of experienced engineers, the design department is fully computerized where in house software has been developed for accurate and fast design.

Core Slitting:

Two high accuracies CRGO Silicon Steel Slitting lines from the UK and one automatic sheet feeding, straightening, cut to length machine from Austria producing a super quality of slit coils with low burr and camber. This ensures the high production capacity and quality of core.

Core Cutting:

The transformer core is made of thin cold rolled grain oriented insulated silicon steel laminations with extremely low loss. TVL equipped with high accuracy automatic core cutting machines. The physical characteristic of the core meets the international standard such as the inherent loss due to hysterics & eddy currents, thickness, brittleness degree of waviness, and permeability.
Core Annealing: Annealing restores the original magnetic qualities of the core by releasing all internal stresses that developed on the core during processing. TVL has a roller hearth furnace to reduce the core loss, the core is annealed at a suitable temperature.

Coil Winding:

Electrical stability,  Mechanical stability, and Thermal stability are the three fundamental requirements of the Transformer design. TVL transformer is designed to meet the services factor such as high electrical & mechanical strength of insulation, coil characteristic, uniform electrical flux distribution, prevention of corona formation and minimum restriction of free oil circulation, winding surge to lightning & circuit breaker operations, etc are taken into consideration.
copper-Casting plant, Copper plant, super enameled plant, and strip covering plant that ensures the consistency of good quality of copper that is a pre-condition for low loss transformer.

Core Coil Assembling:

core coil assembling

Trappings are provided in HV winding for variation of HV to +2.5% and -3*2.5% of rated. Tappings are brought out by means of flexible conductors, heavily insulated with paper and supported by cleats. Tap selection is effected by means of an off circuit tapping switch which can be operated externally. The tapping switch positions are identified and located by means of padlocking on a particular Tap.


Insulation & Impregnation:

The quality of the transformer and especially the dielectric strength response of its insulation depend on the treatment of its active part. For TVL transformers the treatment consists of an alternation of hot air heating and prolonged vacuum so as to remove all moisture from the insulating materials. The oil used for impregnation complies with BS-171 and every consignment received is tested before being pumped into storage tanks.


The tank is made of a steel plate suitable for electric welding. The sidewalls of the tank are corrugated or detachable press steel radiators of high thermal conductivity in order to increase the cooling surface area. All tanks are pressure tested before leaving the fabrication department on the label of test pressure depends on the service voltage specified. All parts-plates, shape, hosting lugs, etc. are welded to ensure greater mechanical strength. Tanks are shot blast to remove rust and scale, cleaned, coated by anticorrosive primer paint, and then enamel finish paint is applied has a high resistance to chemicals and oil. A coat of heat and transformer oil resistant insulating clear lacquer varnish is applied to the all interior surface which have contact with the transformer oil.


Full testing facilities as per BS/IEC are available and these tests are regularly carried out on each unit under expert supervision

Routine Tests:

*Measurement of winding resistance

*Measurement of the voltage ratio

*Measurement of losses


* Measurement of short-circuit impedance

* Measurement of no-load currents

* Measurement of partial discharge

* Determination of voltage vector group

* Determination of percentage impedance

* Dielectric tests

Type Tests:

  • Short circuit test
  • Impulse voltage test
  • Induced voltage test
  • Temperature rise test