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The AVR is automatic voltage regulator and it is a device which is used to regulate or stabilize electrical power supply for electrical or electronic appliances

In this project, therefore, we are interested in the construction of this all important device. Furthermore, we shall discuss the techniques, processes, switching stages and then the working principle of the automatic voltage regulator

Chapter one of this project dwells on the introduction of the project topic. It also talks about the objectives of the project, bringing to mind what we intend to achieve at the end

Chapter two of the project reviews the research works that have been carried out by some other people in this study area. It also discusses on some of the components used in this project

Chapter three gives a detailed account of the basic construction and the operation of the AVR. It also highlights on some other components used, discussing their working principles using both the circuit and block diagrams

Chapter four of this project draws the conclusion and consequently gives the recommendation on how to better the operation of the AVR. It also includes the references and articles consulted in the course of this project.




Certification page                                                   i

Abstract                                                                ii

Acknowledgement                                            iii

Dedication                                                      iv

Table of content                                              v-vi


1.1 Introduction to automatic voltage regulator   1-3

1.2 Objectives of the project                            3-4


2.0 Literature review                                        5-7

2.1 Some of the components used                     8

2.2 Resistors                                                   8-9

2.3 Capacitors                                                 10

2.4 Transistors                                                       11-12 2.5 Relays                                                     13-14


3.0 Basic construction and operation of the automatic

Voltage Regulator AVR                                          15

3.1 Components                                              15

3.2 Transformers                                               15-18

Circuit diagram of the AVR                                19

3.3 The working principle                                         19-21

3.4 The main function of the AVR                       23-25

3.5 The need for voltage regulation/stabilization 25-26


4.0 Conclusion and recommendation                    27

4.1 Conclusion                                                   2728

4.2 The importance of voltage Regulation                  28-30

4.3 Recommendation                                              30

Reference                                                           31




Automatic voltage regulators (AVR) in power supply  unit  is a device  which  is used to regulate  or  stabilize  electrical power supply for  electrical  or  electronic appliances. This device helps automatically to keep the voltage level from the public power supply system constant. In other words, the minimum   and maximum   ranges   of voltage are maintained in order to achieve a constant output     of 220V.

These devices also    serve as     a protective device for appliances connected directly to it, while the AVR is connected directly to the public supply. The protective system  in AVR either regulate or stabilize  it  to  220V output for the  safety of our appliances  or the  fuse in  the AVR will rupture  by excess current  of the surge and thereby cut-off the  incoming   power supply.

The  stabilization and regulation  is achieved  through the control circuit which  include relays and other components  of  various  voltages from the  secondary  winding  of the auto-transformer used in  this  project work.

This control circuitry does the work of cut and boost in the case of higher and lower voltage respectively. If the  supply voltage drops  below  220V down to 180V,the  primary control  does the work of the boost which brings the output  to normal , while  when the  voltage increases beyond  220V up to   260V ( which  is not  ideal),   it does the work of  cut. The coils of the relay are triggered by the 11.5V D.C from the last stage of the operational Amplification. By this arrangement, an improved automatic voltage regulation is achieved and, is hereby presented in this project.

Different  techniques  have been  employed in the  design of AVR circuits in recent times but, in the  design and  construction  of this particular  type, high rise voltage, excess current  due to dangerous condition  externally like  lightening  effect  which  may appear on the  power supply lines were effectively isolated. The  system  chips  and  fragile  devices were protected  likewise  low voltage fluctuations make-brake power supply  from public  power supply were taken  good care  of in this AVR construction.



The automatic voltage regulator of rating 2KVA is a natural choice for remote control device for the consistent voltage level fluctuation of our    power supply system. Therefore, we bear the following in mind as our objective while carrying out this project;

1).  To fully understand  the automatic means of  controlling  and regulating the system, Its practices, design, construction, operation  and application  in public  electric power system  engineering

2). to test the electric power behavior of systems or appliances connected to AVR. Also  to perform both  practices  network computers, televisions, amplifier sets and other sensitive  devices intended  to be  protected  from direct  connection  to public electric power supply.

3). to practically engage in and fully understand the AVR operational modes and technology or configuration in electrical design and construction

4). To enhance  power regulation  and stabilization  technology   via  automatic voltage  regulation  for our electrical and electronics appliances  due to voltage  variation and, incessant  power –fluctuations.


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