H.T. Transformers with Built in Automatic Voltage Stabilizer




It is a very altogether different product basically a combination of Standard Distribution Transformer and HT Automatic Voltage Regulator. The Standard Transformer with OLTC can correct limited voltage variation in certain steps where as Built-in operates steplessly monitoring the output voltage continuously.
The incoming fluctuating H.T. supply is initially stabilized and then fed to the step down transformer and thereby the L.T. Output is maintained within ±1% accuracy. Built – in has the following advantages:

• Space saving
• Reduced Installation cost
• More efficiency
• Reduction in Electricity Bill



1. Capacity :Up to 10000 KVA
2. No. of Phases :3 Phase
3. Frequency: 50 Hz.
4. Voltage Range :11 KV/ 33KV
5. Tapping: +5% to -15% Taps on H.T. Side in steps of 1.25% each..
6. Insulation :Class ‘A’
7. Vector Group :Dyn 11
8.  Duty Cycle :Continuous
9.  Winding :Copper Wound
10.Terminals :As per required


1. Rating & Diagram plate :Earthing terminals
2. Lifting lugs :Thermometer pocket
3. Oil Conservator with drain plug :Air release hole with plug
4. Oil Level indicator :Explosion vent with diaphragm
5. Top-filter Valve: Inspection cover.
6. Silica gel breather :Drain –cum-bottom-filter valve
7. Cooling radiators :Uni / Bi- directional rollers


1. Buchholz relay with alarm and trip contact :Magnetic oil level gauge with alarm contact
2. Pressure Release Valve :Marshalling box to house O.T.I. and W.T.I
3. Cable Box on H.T. Side :Cable Box on L.T. Side.
4. Oil Temp. Indicator with alarm & trip contact :RTCC (Remote Tap Changer Control) Cubicle
5. Winding Temp. indicator with alarm & trip contact :Electronic Automatic Voltage Controller


1. More efficient
2. Non toxic
3. Highly safe
4. Non flammable
5. Space saving by placing near the load end
6. Low Noise
7. Low Maintenance
8. Can be supplied with off circuit links


1. Very Easy to maintain – No Specialize Manpower  is required.
2. Undistorted output characteristics ie. No wave from distortion.
3. Moving parts on L.T. side and its mass is extremely low, only few lb-inch torque.
4. Energy savings.
5. High efficiency (about 99%) and minimum no load losses.
6. Simplicity and flexibility of design
7. On load stepless voltage variation
8. Long service life
9. Impulse tested
10. Regulating coils are wound with rectangular conductors on their edge, thus giving high mechanical strength compared to other designs.
11.Low replacement cost.

1000KVA Built in AVR (Pinnacle, Ghana)

7500KVA Built in AVR (Installed at Dhaka, Bangladesh)

7500KVA Built in AVR (Installed at Dhaka, Bangladesh)

Transformer 5MVA (33/11KV)