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H.T. Distribution Transforms

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Maestro make Sealed/Conventional, Single/Three Phase, 50 Hz aluminium/copper double wound, oil immersed, continuous heavy duty transformers are designed with Class A / Class F insulation to withstand short circuit and impulse test standards. These are robust and durable machines which last for many years.


Core used is made from best grade imported cold rolled grain oriented silicon steel laminations with the hi-tech latest technique of annealing. Reduced core losses and magnetizing the current considerably, core is specially designed to sustain over fluxing up to 12.5%. Individual stamping insulated on both side with oil and temperature resistant insulating material. Core is stamped with steel channels rigidly to reduce the sound level and earthed with electrical grade copper sheet.


The winding are of different type 1)Spiral 2)Crossover 3)Helical 4)Disc, designed to withstand the optimum electrical, mechanical, dynamic and thermal stresses depending upon the current and voltage. The coils are wound with electrolytic grade high conductivity, annealed wire and strips covered with high quality insulation. All coils are reinforced, insulated and impregnated with insulating varnish to with stand the effect of short circuits and impulse voltage shocks. Cooling ducts are provided to minimize the hotspot temperature and temperature gradient between winding and oil.


The Insulation material like pre-compressed boards, blocks, corrugated cylinders, Bakelite tubes, insulating tapes, empire sleeves, glass sleeves, varnish, epoxy bushing, porcelain bushing etc. are used of best quality to ensure long life of transformers. Oil used as a coolant and insulating medium is of best quality confirming to IS:335. Before filling in to the transformers, oil is centrifuged, dehydrated and filtered through ’Stream Line Filtration plant’ and tested to ensure free from moisture.


The Tanks are made from prime quality mild steel sheets, plates and pipes by electrical welding. Proper bracing and stiffeners are provided for robust construction. The tanks are tested as specific pressure for leakage at joints. Sufficient cooling radiators are provided for maximum dissipation of heat during extreme ambient temperatures. The radiators are made from best grade presses steel fins or elliptical tubes.


Tank surface exposed to atmosphere is galvanized / painted with two coats of red oxide paint to provide maximum resistance to corrosion and two coats of epoxy based anti-corrosion enamel paint. Surface in contact with oil is treated with two coats of ‘Oil and Heat Resistant paint’. This paint has more effective resistance compared to ordinary enamel paint against corrosion and oil/heat reactions.


Dyn11, Various vector groups can be provided as per requirement.


Designed for maximum temperature rise at full rated load 40⁰C / 50⁰C for oil and winding of aluminium wound transformers and 45⁰C / 50⁰C for oil and winding of copper wound transformers.


Maestro Transformers are designed for overloading more than normal rating as per IS:6600


H. V. - Bare Bushings or Cable Box, L. V. - Bare Bushings or Cable Box. Disconnecting chambers can also be provided on both HV and LV Cable boxes.


Standard fitting recommended in IS 2026-1977 are provided
1. Rating and diagram plate.
2. Earthing terminals - 2 Nos.
3. Lifting lugs.
4. Oil level indicator (Plain)
5. Drain-cum bottom filter valve with plug.
6. Oil filling hole with plug on conservator.
7. Oil conservator with drain plug.
8. Air release plug.
9. Silica gel air breather.
10. Bi-directional flat rollers.
11. HV terminals-outdoor bushings.
12. LV terminals-outdoor bushings.
13. Radiators.
14. Filter valve with plug.
15. Thermometer pocket.
16. Oil temperature indicator.
17. Externally operated off circuit tap
changing switch.
18. Explosion vent.
19. Sampling value (for 2000 KVA & above transformers only)

Accessories on Request

1. LV and HV cable boxes
2. Winding temperature indicator (WTI)
3. Buchholz relay
4. Magnetic oil level gauge
5. Marshalling box.
6. Disconnecting chamber
7. Oil temperature indicator with electrical contacts (OTI)
8. Pressure relief valve


1. Short circuit with stand test.
2. Impulse voltage with stand test. These are the type tests and can be arranged at C.P.R.I. BHOPAL / BANGALORE and other recognized laboratories on payment if required by the customer.)


Our works is equipped with all requisite testing facilities for quality assurances. Each transformer is tested for all tests confirming to IS:1180 and IS:2026 by qualified and experienced engineers with precision grade instruments. The tests involved are :
1. Measurement of insulation resistance.
2. Measurement of voltage ratio.
3. Check up of vector group and polarity.
4. Included over voltage test at double voltage and double frequency.
5. Separate source high voltage test of HV side and LV side.
6. Measurement of on load losses and magnetizing current.
7. Measurement of load losses and impedance voltage.
8. Measurement of zero sequence current.
9. Measurement of HV winding and LV winding resistence.
10. Measurement of temperature rise of winding and oil of transformers at full rated load.
11. Pressure and vacuum testing of transformer for permanent deflection of body.
12. Check up of dielectric strength of transformer oil. (Test certificate are issued with each transformer.)


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Maestro provides a wide range of Oil Filled Distribution Transformers with On Line Tap Changer (OLTC) which are conforming to the IS and international standards of quality and safety. These transformers are designed and developed using latest technologies and can be provided with a variety of terminations so as to suit the requirements for new installation of products. Optimum efficiency can be ensured by delicate proportioning of core and winding loses using CRGO M3 to M5 MOH Lamination and Electrolytic Grade 99.9% pure copper, with Transposition in L.V. coil for current sharing in parallel Conductors, Electric grade mineral oil, press paper and boards. Thus better regulation is achieved resulting in longer life. Careful and precise designing also reduces noise level to the minimum.


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Maestro Make Copper wound, HT AVR suitable for indoor / outdoor installation, copper wound HT AVR system is a revolutionary landmark in the industry when it comes to voltage regulation and stabilization. Even after the installation of standard distribution transformer the problem of low / high voltage on the LT loss of a plant. The standard off - circuit tapping of transformers can correct limited voltage variation and cannot regulate the voltage while in 'on Load' conditions. We have developed state of the art technology HT Automatic voltage regulator that operates on load, sleeplessly & gives stabilized voltage on the HT side. The fluctuating voltage from Grid is initially controlled by the HT AVR and then fed to the transformer resulting in the constant H.T. Output within +/- 1% accuracy and the biggest advantage being its robust design ; Lesser losses & more efficiency make the distribution transformer to utilize up to 100% capacity.

Liner Type Vertical Rolling Contact Automatic Voltage Regulator (AVR)

In our regulator we are using heavy section of electrolytic grade rectangular copper strip instead of copper wire to minimize the losses & increase the efficiency of equipment. We are also using self lubricating Carbon Roller Assemblies instead of ordinary Carbon Brushes which offers more reliability and trouble free performance of the equipment.

Superior Features Of Maestro Linear Automatic Voltage Regulator

Temperature Rise : It is designed for 30-35 degree C above ambient. Suitable for any kind of ambient temperature conditions.
Core : Core is constructed from Low Loss of CRGO M-4 Grade confirming to latest standards & is fitted & clamped with special built in-house frames to reduce the magnetic noise & to make the structure rigid & robust.
Windings : Use paper covered electrolytic grade copper strip for winding. Cooling ducts are provided to keep the hot spot temperature as low as possible.
Tanks & Paint : Tanks are made of M.S. Sheets with adequate bracing & stiffeners are given a coat of Epoxy Primer & Epoxy paint for better life. Both light grey & Siemens grey (RAL 7032) are available in colour.
Oil : Oil of IS: 335 standard is being used & is filtered before topping.

Advantages of AVR

» Reduction in Breakdown of Electrical Equipments
» Reduction in MDI
» Energy Saving
» Improvement in Power Factor
» Uniform Quality of End Product
» 80% Depreciation as per Income Tax Act