1. Automatic Voltage Regulator

2. Automatic Voltage Regulator
Why do we need them?
It is known that Voltage(V) of a power supply system must be maintained at a constant value.
Other wise the performance of any motor/machinery will drop considerably.
When any new load is given to an un-regulated AC Generator, the V drop is more substantial V
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3. Automatic Voltage Regulator
…Why do we need them?
Close control of generator volatge is required to prevent such dips in V.
This control is achieved by an Automatic Voltage Regulator (AVR)
The real need of the AVR is to deal with the voltage dip following the sudden connection of extra load and to restore the rated Voltage without undue overshooting and regeneration(i.e. volatge hunting)

4. Automatic Voltage Regulator
How does it work? V
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There are two stages that follow when the extra load is connected.
Transient Stage(followed by recovery)
Steady state condition
Response time for restoration within 3% of voltage dip is 1.5seconds
Steady state voltage regulation at any p.f. within rated p.f. and unity p.f Is +/-2.5%

5. Automatic Voltage Regulator
How does it work?
There are three basic parts to an AVR
Error detecting element
Correcting Element
Stabilizing Element

6. Automatic Voltage Regulator
Block Diagram

7. Block diagram Automatic Voltage Regulator
The AVR senses the DG output voltage and acts to alter the field current to maintain the output voltage at its set value
The excitation voltage can be set by the hand trimmer
The VOLTAGE SENSING unit transforms down, rectifies and smoothes the generator output voltage. This produces DC signal proportional to the actual generator voltage.
This signal is compared with the set value at the COMPARATOR
The ‘error’ signal from the Comparator is used to control the excitation current through ERROR AMP. and CONTROLLER.

8. Automatic Voltage Regulator

9. Thank You