Description
Manufacturing facilities:
TVL is located at Savar, a clean & green Environment. There are separate shop 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 have liberal floor area for work.
Design & Engineering:
TVL has a group of experienced engineers, design department is fully computerized where in house software has been developed for accurate and fast design.
Core Slitting:
Two high accuracy CRGO Silicon Steel Slitting lines from UK and one automatic sheet feeding, straightening, cut to length machine from Austria producing super quality of slit coils with low burr and camber. This ensures the high production capacity and quality of core.
Core Cutting:
Transformer core is made of thin cold rolled grain oriented insulated silicon steel lamination with extremely low loss. TVL equipped with high accuracy automatic core cutting machine. The physical characteristic of the core meet the international standard such as the inherent loss due to hysterics & eddy currents, thickness, brittleness degree of waviness and the permeability.
Core Annealing: Annealing restore the original magnetic qualities of core by releasing all internal stresses that developed on core during processing. TVL have a roller hearth furnace to reduce the core loss, core are annealed in a suitable temperature.
Coil Winding:
Electrical stability
Mechanical stability and
Thermal stability are the three fundamental requirements of 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 in to consideration.
CopperUp-Casting plant, Copper plant, super enameled plant and strip covering plant that ensure the consistency of good quality of copper that is a pre condition for low loss transformer.
Core Coil Assembling:
Trappings are provides 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 transformer and especially the dielectric strength response of its insulation depends on the treatment of its active part. For TVL transformers the treatment consist in 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 in to storage tanks.
Tank:
Tank is made of a steel plates suitable for electric welding. The side walls of tank are corrugated or detachable press steel radiator 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 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.
Testing:
Full testing facilities as per BS/IEC are available and these tests are regularly carries out on each unit under expert supervision
Routine Tests
- Measurement of winding resistance
- Measurement of 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 volage test
- Temperature rise test
