Automotive voltage inverter is an important area in power system engineering.  It is the process of using a 12v DC from the battery to achieve a 220/230V AC through the help of oscillator, drivers, power transistors and transformer.  The stages are battery to oscillators, oscillators to drivers, drivers to power transistors then from power transistors to transformer which is capable of giving out 220/230V (1000w) as an output.   A 1.25KVA (1000w) voltage inverter was constructed, tested and certified okay.  Since the inverter as constructed to step-up voltage, the power transformer is used as step-down for charging and as step up transformer for inverting.   This project helps in the improvement of the epileptic power supply we are having in Nigeria and it also reduce the high level of power dependence in Nigeria by serving as IPP’s (Independent Power Plants).  The project as run in school helps in equipping the students in the practical aspect of the course.



Title page                                                                               i

Certification page                                                                  ii

Dedication                                                                              iii

Acknowledgement                                                                iv

Abstract                                                                                  v

Table of content                                                                    vi


Introduction                                                                            1

Analysis (review of existing system)                                   2

Aims and objective                                                               3

Scope/Limit of the project                                                    3

Application                                                                             4


Literature review                                                                    5

Introduction                                                                            5

Brief review of used components                                                 5

Capacitor                                                                               7

Resistor                                                                                  8

Relay                                                                                      11

Transistors                                                                             13

Diodes                                                                                    24

Switches                                                                                26

Operational amplifier                                                            27

Transformer                                                                           28

A.C. Voltage meter                                                                29

Oscillator                                                                                29

MOSEFET                                                                                       29


Design and analysis                                                             33

Introduction                                                                            33

Methodology                                                                          34

D.C. Supply (input voltage)                                                  35

Voltage regulator                                                                   35

Control logical circuit                                                             35

Frequency generator                                                            36

Phase splitter                                                                         37

Driver                                                                                      37

Step-up transformer                                                              38

A.C. supply (output voltage)                                                          38

Methodology II                                                                       39

The unregulated supply (input voltage)                                       39

Isolating relay                                                                        39

Step-up transformer/rectifier circuit                                     40

Changing control/logic comparator circuit                          41

Theory and calculation                                                         43

Circuit diagram casing design                                             44


Constructions test and result                                               46

Introduction                                                                            46

Problem encountered                                                           47


Conclusion and recommendations                                              48

Conclusion                                                                            48

Recommendations                                                               48

References                                                                            50






Electrical power being one of the basic criteria for the measurement of development in a country is basic necessity.  It is the responsibility of any responsible government to provide stable, cheap and uninterruptible power supply to its citizens through the provision of adequate electrical infrastructures.


Since the advent of the first electricity, generator, and many other forms of generators have been development for the conversion of various forms of energy into electricity.   These includes, hydro power generator in hydro power stations, gasoline and diesel fired generators, gas turbine generators, solar generators, steam turbine generators,  wind turbine generators and fuel all electric power generators.  All the above forms of generators have proved potent but due to disadvantage or drawback or one lead to he invention of another.


All these generators mentioned above are:

  1. Difficult to step up (gas plant)
  2. Expensive (fuel)
  3. Time consuming
  4. Noisy during operation (generators)
  5. Pollution


When all these were put into consideration he invention of inverters became necessary due to its following features as listed below:

Small in size

Easy to set up

Less expansive

Noise free


An inverter is a DC – To-AC converter device that is one efficient in operation.  Hence in advanced countries the use of solar panel is being employed to convert radiant energy, the butteries for effective operation of the inverter.


As the saying goes “necessity is the mother of invention” therefore, the need for inverter has become necessary in a country like Nigeria to help boost power supply so as to enhance economic growth of the people and the entire nation at large



The un-automated inverter is not really an inverter is just made up of circuit compilation via transistors and transformer to produce A.C voltage.


Most foreign inverters are low power inverters that cannot withstand a load up to 12.5KVA due to the use of some fragile components.  E.G. BJT transistor.


Some local technicians can construct an inverter with no control, i.e. some additional features to enhance the performance of the inverter during operation.



This project is designed to improve on the existing system by not only having in place those thing is some of existing one like automatic trip off when battery voltage drops fully charge, cut off when the battery has reached its peak voltage. The use of MASFET, as rectifier is to charge the battery (in built charger).



The design of this project is limited to input voltage of about 12v capable of delivering circuit ranging from 45A to 400 A D.C.


Although it can be extended further but for high capacity the input voltage should be increased as to minimize the current.  The effect of this is that, the higher he current the larger the cross sectional area of conductors that will be used.


This project can withstand load range from – – 800w, 50Hz at 20 – 220v input.


A load of 1000w cannot be attained due to some losses from various part of the design such as transformer losses.  1000w is the power at no load.



His project can be used to supply A.C. of 200 – 220V from input voltage of 12V, provided the input current dos not rise above 15A, when a load of 700w is applied.