transformers1 A transformer is an electrical device that transfers energy between two or more circuits through electromagnetic induction. A varying current in the transformer’s primary winding creates a varying magnetic flux in the core and a varying magnetic field impinging on the secondary winding.
This varying magnetic field at the secondary induces avarying electromotive force (emf) or voltage in the secondary winding. Making use of Faraday’s Law in conjunction with high magnetic permeability core properties, transformers can thus be designed to efficiently change AC voltages from one voltage level to another within power networks. A wide range of transformerdesigns is encountered in electronic and electric power applications. Since the invention in 1885 of the first constant potential transformer, transformers have become essential for the AC transmission, distribution, and utilization of electrical energy.As consistent guarantee of the highest quality Distribution Transformers are manufactured from CRGO (cold rolled grain oriented) silicon steel. Quality control is carried out at all stages of production while final routine and type tests are performed in our well equipped testing laboratory according to IEC-76, BDS 1081, ANSI, AEC and BSTI standards.
Standards : IEC 76, BDS-1081, ANSI, VDE.
Frequency : 50Hz, 60Hz (on request)
Ratings : 5 KVA – 10000 KVA
Primary voltage : 11 kv and up to 33 kv.
Tapping : ± 2.5 %; ± 5 % or ± 2 x 2.5 %; -7.5%
Secondary voltage : 400 to 433V other values may be offered Double low voltages with 7 LVbushings can be offered with full rating on both voltages or with reducedrating (75%) on load.
Rating(kva) Height/H(cm) Length/L(cm) Width/W(cm) Weight(cm)
100 132 100 63 650
150 145 105 88 850
200 150 112 93 1000
250 158 113 95 1100
315 160 120 97 1300
400 165 123 98 1450
500 165 124 102 1725
630 170 136 103 1970
750 185 155 112 2250
800 225 170 113 2575
1000 215 185 115 2850
1250 225 190 116 3725
1500 230 200 120 4300
2000 245 210 130 4750
2500 250 215 135 5900
3000 255 245 170 7000
5000 262 262 300 11000
10000 304 335 400 19000
Notes: All dimensions are shown including radiator and conservator tank.
transformers5 The core is built with laminations of high grade grain-oriented silicon steel. The special cutting and stacking methods result in low no load losses and low noise levels. Wound on mandrel, the core is annealed at the highest temperature to relieve mechanical stress and fix into the design shape.Low cold rolled grain oriented silicon steel strip. The core is built with laminations of voltage coils are normally larger layer wounds using paper insulated copper conductor. Circular type and rectangular type windings are respectively used for relatively large or small type of transformers. The coil has to allow the liquid insulation for cooling. It causes uniform heat dissipation due to losses. The round conductor windings consist of individually wound coil sections connected in series to produce phase winding. We use high grade Imported copper for winding and export quality super enamel wires for HT windings. HT and LT coils are checked for inner diameter, outer diameter, axial length, number of turns and resistance.
The dielectric circuit of transformer which isolates the magnetic & electric circuit & their parts, insulation
papers and press board of high quality are used for our Transformer. Moisture content of the insulationpaper is very minimum. Drying system removes almost all moisture from the insulation structure and finally from the transformer.
High voltage and low voltage bushing are of wet process porcelain terminals suitable for copper or aluminum conductors. All the bushings are top mounted.
Transformer oil is procured from reputed manufacturers. It is tested for resistivity dielectric dissipation factor, acidity, flash point, pour point, break down voltage and inter facial tension as per BIS & IEC. No furtherdrying will be required before putting into operation.

Insulating oil are as follows:
Specific gravity at 15ºC 0.87
Viscosity at 75ºC 5.5 centistokes (max)
Viscosity at 30ºC 19.0 centistokes (max)
Flash point 145ºC (min)
Dielectric strength 50 kv (min), 12.5mm
Diameter spare electrode gap length 2.5mm
transformers6 Tap changer is made of high quality homogeneous insulating board or synthetic resin mold is mounted below oil level for changing the connections of taps in primary windings. In almost all our distribution transformers, we use imported tap changer from reputed Company.
transformers7 Conservator Tank is detachable by providing a flange at its point of RADIATORS connection to the tank cover. Transformer tank is made with steel sheet and covers are fabricated by welding. Tank is tested under pressure for finding any leakage. Tanks employed for housing the core coil assembly are mechanically strong. Tank finish consists of three coats. Each coat is applied uniformly and cured at even temperature. For properly making of radiator is very important. Each individual element and radiator under assembled condition is tested with air pressure of approximately 3kg/cm2. Tank painted by a zinc riched primer coat and two finishing coats as required by the customer. Powder coated radiator is also available on request.
- HT/LT Bushing with terminal connectors
– Oil level Indicator- Oil drain plug
– Buchholz relay- Gate valve
– Tap changers
– Lifting-Lug
– Thermometer (for 3 phase transformer)
– Name plate with connection diagram
– Silica gel breather for the conservator tank
– Pressed steel radiator- Earthing terminal
- Flexible connector from LV Bushing to BBT end connection unit.
– High voltage plug in connectors.
– Marshalling box with accessories for thermal protection.
– Temperature measurement by means of a PT100 resistor in the middle phase, with digital or analog
indicator with or without contacts.
– Digital display of temperature on the 3 phases with contacts and storage of maximum values.
– Fans with control and control box for forced cooling (increases the rating with 10%)
– WTI, OTI, Buchholz Relay
– Vibration dampers.
Routine Test
* Insulation resistance test
* Core insulation test
* Winding resistance test
* Voltage ratio & polarity test (vector group test)
* No load loss & exciting current measurement test
* Load loss & impedance voltage measurement test
* Dielectric strength test of oil
* Power frequency (separate source) voltage withstand test
* Short-circuit test* Function of tap changer test
* Heat-run test at ONAN and ONAF rating (specify)
Test certificates are issued for all the above tests on request
Type Test
* Impulse voltage withstand test
* Temperature rise test
* Oil leakage test
* Over load test
* Noise level test
PEtelCO committed to its valued client for trouble free operation of our supplied equipment and under make warranty for free replacement of any part or parts failing due to manufacturing defect, which shall not include normal operational wear and tear for a period of 18 Months from the date of delivery of equipment and 12 months from the date of commissioning.
Repairing of power transformer are also taken care of in our factory or at site of installation. Rectifier and AC/DC welding transformer are also be repaired on request. Retrofitting in feeder unit and out feeders with any kind of circuit breakers, including re-winding & repair of transformer, fittings. For repairing of winding &
up to 33 kV assembly and OLTC utility and big substation owners can contact us in full confidence.

December 2023
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