H.T. Automatic Voltage Stabilizer – Power Star image image

H.T. Automatic Voltage Stabilizer (HT AVR / HT Servo Stabilizer)

RANGE : Upto 8000 KVA in 11 & 33 KV Class.


H.T. Automatic Voltage Stabilizers are used to get stable input voltage, irrespective of the voltage variations received from electricity authorities. Additionally, these stabilizers also prevent the transformer and other electrical equipment from getting overloaded. Wide voltage variation ranges are taken care continuously and in on load condition. The variations of more than ± 1% of the rated output voltage are sensed through solid state relay. This relay operates on 230 V, 1Ø supply and sends signals to the stabilizer’s motor, which drives the roller mechanism in a direction to bring voltage to the rated output voltage.


H.T. Automatic Servo Voltage Stabilizers have helical coils mounted on a conventional laminated core. Carbon rollers are assembled on a fibre glass carrier board and are traverse to the length of the coil track. The rollers are connected to the electric output terminals. Nearby the regulating coil, a number of compensating winding is connected in parallel, which are short circuited to reduce the effect of core-flux fringing. It also keeps the reactance of the regulator constant at any position of the rolling contact.


  • Utilization of the Distribution Transformer is to its full capacity as the H.T. AVR shares the load of the Transformer and the connected load.
  • Losses are less as the incoming voltage either low or high is corrected at the initial stage only.
  • Fluctuations in the H.T. Supply are not passed on to the Distribution Transformer.
  • Installation Cost is less in comparison to L.T. Automatic Servo Voltage Stabilizer, for higher ratings.
  • Single Unit of H.T. Automatic Servo Voltage Stabilizer can be connected to more than one Distribution Transformer.
  • Economical for huge capacities like 2500 KVA and above or for wide voltage fluctuation range (eg. 8 KV – 13 KV, 28 KV – 36 KV etc.)
  • Can be placed anywhere on the feeder line.
  • Motor fitting is external, so any change of the motor or motor shaft can be easily done without opening the top cover.
  • Output Voltage of H.T. AVR remains constant at any connected Load and up to full load.
  • Response time for Voltage correction is 20 micro seconds.

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