Basic of automatic voltage regulator

Basically the AVR or Automatic Voltage Regulators function for generator is to ensure voltage generated from power generator running smooth to maintain the stable voltage in specified limit. It can stabilize the voltage value when suddenly change of load for power supply demand.

If the generator running in parallel condition,the AVR can controlled the voltage that it produce to ensure of equal value for reactive load sharing.

For the big system of interconnected power distribution with parallel design,it must have a full controlled and transient stability particular must added for requirement to the Automatic Voltage regulator for generator.

What is Automatic Voltage Regulator (AVR)

The AVR can operated in two condition controlled.It is from manual control or automatic control with standard limited parameter that required for generator.

This controlled must be provided if it not available for the generator system to ensure it smooth running without any problem.


Basic principles for AVR

A signal proportional to generator terminal voltage obtained from the rectified output of a voltage transformer is compared to a stabilized reference voltage obtained within the regulator.

If it detected any abnormal,different or error signal, it will amplified and control the excitation supply, increase or decrease the input to the main field winding or exciter field.The main purpose is to reduce the error signal to zero or an acceptable value.

Adjustment of the set voltage is obtained either by adjustment of the reference voltage or by adjusting the proportion of machine voltage compared to the reference voltage. The stabilizing loop is included to prevent hunting.Below is basic diagram for AVR circuit.



  1. haitham hashim says

    Important topic, the explanation Excellent

  2. is it safer for my PC if i use an AVR or a UPS when a blackout occurs?

  3. kaminda says

    this s good attempt and help full 4 me.thanks

  4. basavaraj says

    good notes.

  5. srinivas says

    sir if possible give references to topic you are discussing, so that we can study in detail. any way its good. thank you.

  6. If you are going for finest contents like myself, only go to see this website all the time since it presents feature contents, thanks

  7. ankur sharma says

    Hi plz explain me more about avr

  8. good

  9. I have a 2 KVA generator and have rewound its armature(Stator) myself.After installation and connecting AVR and starting engine, power is not available.

    However,if 40V AC from house mains is given through a stepdown transformer and connecting its output wires with yellow wires of AVR on input side(leaving brown and blue wires open), power is available and excitation winding of stator also give 50V AC. What could be possible reason for generator not developing power when AVR yellow wires are connected with AVR and its output wires blue and yellow are connected to field terminals.In this case also I have not connected brown and Blue wires with stator winding.

  10. Tim Murphy says

    If you use any AVR from one portable to another what will happen

  11. ARVIND RANA says

    T1& T2 both are connected to the AVR supply then after supply goes to the lt panel where is , my 2 TRANSFORMER, T1&T2 , AND MY T2 WAS IN OFF CONDITION SO WHY burent my LT PANEL TRANSFORMER -2 …..

  12. kavitha says


  13. Hello..
    i am trying to develop a control system for the generator’s output.. the generator has only 50W output. is it possible to maintain and control the output using AVR? and how? i appreciate if you can answer my question.

  14. David David says

    hi i need a help im having a generato but we a using the AVR but now the problems the voltag of the genset its going up and down what is the problems ?

  15. David David says

    can you you answer me please help me!

    • Lotty Sondashi says

      we have a generator of 500kva, it runs ok, but when we load it to half the capacity th engine stalls.
      We checked the turbo charger – ok
      Injectors -ok
      Air, oil and fuel filters – changed to new ones, but still stalls
      what could be the problem

      • Lotty Sondashi says

        Is there a way of testing an avr on a generator while in circuit and generator running?

  16. I’ve 1set generator 2500wtts inside AVR are not function can i use 10kva volt regltr getting from gen set to out come 10kva

  17. The automatic voltage regulator is used to regulate the voltage. It takes the fluctuate voltage and changes them into a constant voltage. The fluctuation in the voltage mainly occurs due to the variation in load on the supply system. The variation in voltage damages the equipment of the power system. The variation in the voltage can be controlled by installing the voltage control equipment at several places likes near the transformers, generator, feeders, etc.

  18. The main functions of an AVR are as follows.

    It controls the voltage of the system and has the operation of the machine nearer to the steady state stability.
    It divides the reactive load between the alternators operating in parallel.
    The automatic voltage regulators reduce the overvoltages which occur because of the sudden loss of load on the system.
    It increases the excitation of the system under fault conditions so that the maximum synchronising power exists at the time of clearance of

  19. AS'AT RAHMAT says

    I get your point but I only don’t know what is firing gear here? AVR doesn’t relate to engine right? So what’s that? Please anyone answer it if you know and if u don’t mind

  20. naser abbas kafi says

    AVR like the mind in the body ,
    its mission:
    to regulate out put voltage in smooth shape
    to protect generator wingdings from high heating sudden

  21. thank you so much


  1. […] already discuss about AVR function and basic operation in my last post.Please refer to basic of automatic voltage regulator.i hope it can make a clear view and understanding about AVR function in […]

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