Automatic Voltage Regulator in Generator

Automatic Voltage Regulator have been discussed in this article, and the component associated with it. AVR is used on the ship generators and as name suggest it is used for voltage regulation in case there is a increase or decrease in power demands suddenly.

AVR can be called as the governor for the generator when  it comes to voltage it generates. In absence of AVR generator will not be able to maintain a constant voltage at the outlet.

Automatic Voltage Regulator

It will be easy to understand it this way:
Consider there is a change in load on the generator like starting of a pump or stopping of the same.
So if the pump was started it will lead to drop of a voltage across the output. This drop in voltage is mainly because of drop of voltage across the internal windings.
Now if there is no voltage regulator then it will take lot of time for generator to come back to the original voltage output. And it seems totally unreliable power system.
To counter such problem, an AVR is fitted in the general system, which will correct the voltage or you can say the winding excitation for the generator and will correct the voltage in range of 2.5% upper or lower depending on the generator load.
For larger change in the loads like thruster or cranes, more limit of around 10 – 15% is given.

Components of AVR

Though it seems very simple as how AVR works but it doesn’t. It has all the complex components to sense, amplify and correct to maintain the constant voltage.

Below diagram shows the components of a modern AVR used widely on all the ships. It consists of following components:

  • Thyristors
  • Transformers
  • Transistors
  • Rectifiers
  • Zener Diode
    Automatic Voltage Recorder

Sensing element is quite important here as it will read the drop in voltage, rectify it and make a similar equivalent low dc voltage signal. Now this DC signal produced by the sensing unit is to be compared by the one which is set already and compared by zener and resistors.

Now the comparator will generate a error signal which will be having same voltage by which main voltage needs a correction. And it will be amplified in order to operate the thyristor.

Thyristor is a precise switch which operates when the voltage is applied on its gate terminal. So the signal which was amplified is applied to the thyristor and it is regulates the field current across the winding of the generator.

But more components are joined together with AVR, which are as follows:

Overvoltage or under voltage trips are fitted to safeguard the generator.

When two generators are to be run in parallel, AVR gives a good sharing of current.

When generator starts, AVR will help in quick generation of voltage and reaching it set limit faster.

More stable function of generator with quick response.

So these were the additional advantages of using an AVR. This was all on the topic of AVR. Hope you enjoyed reading it. If you have any suggestions or doubts, please comment below.

MG Staff

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