Automatic Voltage Regulator Presented By: Rajarshi Ghose Dastidar. Roll no. 149

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

Close control of generator voltage 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. voltage hunting)

There are two stages that follow when the extra load is connected. Transient Stage(followed by recovery) Steady state condition V time

How does it work? There are three basic parts to an AVR: Error detecting element Correcting Element Stabilizing Element

Block Diagram

The AVR senses the DC 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.