HT AUTOMATIC VOLTAGE REGULATOR, this is also a low profile product in the industry and many may not be aware of this product either. But, this product is in existence and successfully serving a huge clientele from past few decades. Now, we at Red Phase has taken the initiative to reintroduce the product in the industry and most importantly manufacturing with its trusted original UK Based mechanism & designing.

Red Phase offers revolutionary state of art Transformer with Built In AVR, which is a combination of HT AVR and a standard distribution transformer. The fluctuating HT voltage from Grid supply is initially controlled by the HT AVR with accuracy of +/-1% and then fed to the transformer which transforms in its standard ratio to LT voltage. Subsequently, stabilized HT voltage will result in a stabilized LT voltage with accuracy of +/-1%. Basically, input will be 11/33KV and output will be LT voltage with +/-1% can be obtained through a single product, can be understood better through schematic diagram mentioned below:

Transformer with Built In AVR reduces the installation cost of the plant and even saves the required space in comparison to Transformer with separate Stabilizer. One of the major benefits is the ability to make distribution transformer to be utilized up to 100% capacity because of the reason that transformer is fed with the rated voltage which is not obtainable when the voltage drops before the transformer subsequently current becomes high and hampering transformer capacity utilization. Another main advantage is that very low input ranges in higher ratings (from 5KV – upto 5000 KVA) can also be stabilized which is not feasible and practical through LT AVR because of the high current and neither through OLTC because of its limited variation range.


  • Compact Design
  • Minimum Power Losses
  • Better Efficiency
  • Low Input ranges can be stabilized in High Ratings
  • As low as 5KV-12KV upto 5000 KVA
  • Low Maintenance
  • Trouble Free operation
  • Long service Life
  • Space Saving
  • Reduced Installation Cost
  • Reduced in Electricity Bill
  • Suitable for corrosive industrial sites

Advantages of HT AVR

HT AVR/Built In AVR Over Transformer with OLTC

S.No. HT AVR/Built In AVR Transformer with OLTC
1 Voltage control is entirely step less, thereby providing close tolerance on the desired output. Voltage control is in discrete steps and the available would be dependent on step voltage.
2 The mechanical movement of the regulator is very simple and consists of chain drive, which moves the roller carrying carrier board. Hence the periodic maintenance is very simple. The mechanical movement is relatively complex, comprising of Geneva Operating mechanism, spring-changing system and so on. Maintenance is complicated and can be done by professional only.
3 Preventive maintenance necessitates change of carbon rollers only as this being the only moving component undergoing wear and tear. Replacement cost and process is low and easy. Number of moving components is more i.e. moving contacts, fixed contacts, gear trains, transition resistors and many more. Hence the wear and tear is much frequent and maintenance process is costly and can be done by professional only.
4 Output voltage of AVR remains constant at any connected load and upto full load. Output voltage of transformer drop down under load conditions from rated No-Load voltage depending upon the percentage regulation of the respective unit and percentage of load.
5 The movement of the roller on the winding of the regulators is at low voltage and does not cause sparking and subsequently there is no contamination of transformer oil. Saving oil maintenance cost. The mechanical movement causes sparking on every tap changing as OLTC is fitted on high voltage winding causing oil to carbonize and leading to acidity. In due course, the entire OLTC oil has to be changed periodically, which is expensive and time consuming.
6 Life of equipment is high because of stepless nature and smooth control and can be further increased by simply changing inexpensive carbon rollers after. Life of conventional "OLTC" manufactured in india is 1,00,000 operations on "No-Load" which is reduced to 40%-50% On-Load conditions. Replacement cost is high and time consuming.
7 Can be placed anywhere on the feeder line. Can be placed only on the receiving end.
8 Externally fitted, Step Synchronous drive motor is used. Making it easier to service without much hassle. Shaded pole motor is used, fitted inside the housing. Maintenance is much more complicated and time consuming.


1 Since the stabilized voltage is fed to transformer, transformer will be used to its rated capacity. Since the transformer is getting fluctuating supply voltage, the unit cant be utilized at its rated capacity and the rating of the transformer will be restricted to the ratio of minimum supply voltage by rated voltage.
2 The efficiency of the transformer will be better since it is fed with rated voltage. The efficiency of the transformer will be lower as the transformer is not fed with proper voltage.
3 AVR is installed before stepdown transformer and stabilized HT supply is fed to the input of the transformer. AVR is installed after the stepdown transformer, fluctuation HT supply is fed to the input of the stepdown transformer.
4 Since the supply to the transformer is at stabilized voltage, the transformer is protected from low/high voltage fluctuations. Since fluctuating voltage is fed to the Transformer, the unit will not be protected from Lower/Higher voltage fluctuations.