Automatic voltage regulator for generator

The AVR ( automatic voltage regulator ) is suitable for supplying power to the fields of either brushless or commutator type exciters and will maintain the A.C generator voltage within plus and minus 1% of the preset value with paralleling.

When the load varies between no load and rated load and with a frequency changes more than plus minus 4%.Upon application or rejection of rated load,the generator voltage recovers to plus and minus 1% within 0.3 second on most AVR exciter in A.C generator combination.

The AVR is suitable for operation in ambient temperature up to 50 ‘c and will deliver a power output of 150 watts with a max. current of 3 A.Under some circumstances the A.C generator wave shape changes considerably from no load to rated load.

It is due to the type of load,hence the r.m.s average or peak voltage does not stay in proportion.In this situation,i.e : greater than 10% harmonic distortion,the voltage regulation may be outside the limit quoted.

 How the Auto voltage regulator (AVR) operate?

When rated load is switched on to A.C generator the voltage fall,typically to approximately 70% of its no load value.If the A.C generator voltage is to be maintained near to its no load value,then its excitation must be increased progressively in proportion to the amount of load or more correctly in proportion to the fall in voltage.The AVR perform this task.

The voltage to be regulated is derived from the line UR and VR of the A.C generator and is potentially divided by the resistance chain R1,R2 and R3.The signal appearing between terminals T2 of potentiometer RV1 and the junction of C1 and R3.

Rectifier diodes D1 and D2 rectify the signal voltage.An error signal is produced by the difference between the signal voltage and a stabilized reference voltage developed across the zener diodes D9 and D10.Capacitor C1 smoothed the signal.This error signal is applied to the base emitter circuit of VT1.The A.C generator voltage is adjusted by the potentiometer RV1.

For more detail about AVR diagram and operation,please refer to my post : Basic of AVR and operation


  1. haitham hashim says

    Topic is very beautiful and important information in it, God bless you from all harm, thank you very much

  2. Sathish says

    In my plant having 43 Mw BHEL generator and bhel AVR also in that having two modes. PF regulation and MVAR regulation if we r maintaining the grid side reactive power our power factor also vl maintain properly for smooth operation. In MVAR regulation giving one pulse the response variation is normal but kept in PF regulation the response variation is more so which regulation is best what is the different between these two regulations plz explain this

  3. kurniawan widi pramana says

    Hmm, do you have any pictures or diagrams that can explain the operating principle of AVR in generator? thank you for sharing it to us..

  4. Hendrix Leva says

    I need to test the AVR of International Electric Co. Type GX300PR.I need help, anyone still a copy of operation manual for this AVR.
    Thank you

  5. ajmal khan says

    ajmal khan

    it is useful information about avr but i need fully curcuits and manual.which is helpful me.




  7. ojo henry says

    Cost of sx460

  8. I absolutely love your blog and find many off your post’s to be exactly I’m looking for.

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  9. Hemantha says

    Dear sir,
    One of our power house is having Blakstone 11Kva 4 Generators. The type of the AVR has fixed in BRUSH which is now Obsolete in the company. EXE voltage is 240 and EXE amp is 34.5 A. i tried to repair the AVRs and spare parts also obsolete. what can i do. do you know any AVR model which we can fix with synchronous facility.

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  11. Josephson says

    Pls can you help me with the schematic diagram of AVR circuit for generator or alternator.thank u

  12. Rajat Dhiman says

    we have naren excitaion panel..
    problem is that our excitaion is not reach at desireable level..due to this .generating voltage is not increases ..what i do

  13. Can I use brushed type generator Avr to brushless generator

  14. Sir I am trending in ganretor part’s avr all types only Marin splay

  15. Java Development says

    Thanks for this interesting post, I have shared it on Facebook.

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  18. Candyuse says

    From many manuscripts of Antiquity

  19. Joseph says

    Please provide a diagram of sx460 connection (wiring) on a three phase generator 8kva with commutator (brushes).

  20. Beaternzg says

    The most common form

  21. Seriesrmb says

    ancient and medieval Latin,

  22. Samson says

    Am havi a Hisaki honda hk8000dxe and the out put power is 40v. Can it be AVR having the problem? Pls help.

  23. Samson says

    Am havi a Hisaki honda hk8000dxe and the out put power is 40v. Can it be AVR having the problem? Pls help.


  1. […] source to the rotor field coil.Excitation system produce the field current and it controlled by the automatic voltage regulator (AVR).I already discuss about automatic voltage regulator on my last […]

  2. […] Automatic voltage regulator for generator – Electrical … – The AVR ( automatic voltage regulator ) is suitable for supplying power to the fields of either brushless or commutator type exciters and will maintain the A.C …… […]

  3. […] 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. […]

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