Construction Of UPS Using 12V DC For 240V AC Output

Project and Seminar Material For Electrical Electronics Engineering EEE

Project and Seminar Material For Electrical Electronics Engineering EEE


An uninterruptible power supply has been designed, constructed and tested. It has a battery driven inverter that gives an output of 1000VA, thereby inverting a 12V D. C. source to 240V ac output.

The power unit was able covert the 240V ac line supplies from NEPA to DC supply and also change the batter by converting the AC supply to DC output required for battery charging. The IC type multivibrator or oscillator amplify the DC from the battery and give an output of 50Hertz required by electrical appliance.
Finally, the UPS was able to generate a rating of 1000VA, 240V ac from the battery supply when there was power failure and it gives square wave of 50Hz frequency.

This project is divided into six chapters.

Firstly, the introduction, history and development of the UPS with aims and objectives.

Secondly, literature reviews, meaning of UPS, types of UPS and the functions of UPS, components of the UPS.

Thirdly, the transformer, fourthly, the battery charger/rectification, block diagram, schematic diagrams and principle of operation of the UPS.

Finally, design and construction of the UPS, conclusion and recommendation.

Table Of Content

Preliminary Page(s)

  • Content page
  • Title
  • Certification
  • Dedication
  • Acknowledgement
  • Abstract
  • Table of Content

Chapter One

1.0 Introduction

  • 1.1 History and Development
  • 1.2 Aims and Objectives of the project

Chapter Two

2.0 Literature Review

  • 2.1 Meaning of UPS
  • 2.2 Types of UPS
  • 2.2.4 Functions of a UPS
  • 2.3 Components of a UPS

Chapter Three

3.0 Transformer

  • 3.1 Definition of Transformer
  • 3.2 Principle of operation of a transformer
  • 3.3 No load transformer
  • 3.4 On Load transformer
  • 3.5 Basic transformer Component
  • 3.6 Electric circuit design
  • 3.7 Rating transformer
  • 3.8 The former
  • 3.9 Lamination
  • 3.10 Design specification/data
  • 3.11 Determination of number of turns
  • 3.12 Fault finding in transformer
  • 3.13 Losses in transformer
  • 3.14 Types of cooling
  • 3.15 Efficiency of a transformer

Chapter Four

4.0 Battery Charger/rectification

  • 4.1 Full wave rectification
  • 4.2 Battery

Chapter Five

5.0 Block diagram, schematic diagram and principle of operation of the UPS

  • 5.1 Block diagram, of a UPS
  • 5.2 Description
  • 5.3 Switching circuit

Chapter Six

6.0 Design construction of UPS

  • 6.1 Assembling of all sections of the UPS
  • 6.2 Construction of the UPS
  • 6.3 Soldering process
  • 6.4 Conclusion and Recommendation
  • Reference

Chapter One

1.0 Introduction

A machine has been defined as a device that helps in doing work easily and accurately when energy is applied. Also electrical energy is one of the most useful source of energy for the operation of both industrial and household machines. Therefore, electricity has been said to be an instrument for the industrization and empowerment of man for better standard or living. Since most of the industrial and household machines are digitally operated when there is power failure, the commands (information) stored in their memory loss out, this makes their execution difficult and possible cause damage in the production activity.

This electric power failure is of critical concern in the operation of most industrial and household equipments (machines) such as data processing systems, health case equipment (machines), telecommunication links, etc. Therefore, since power outage is inevitable in Nigeria, Its damage to the smooth running of these digitally operated device can never be ignored.

Alternatively, a standby power supply such as automatic diesel/petrol generator set have been employed to check the problem, but due to high cost of installation and running of such generator sets, can only be afforded by organizations and few individuals.

Also, there are commercially available uninterruptible power supply (UPS), as medium and low capacity standby power supply. Therefore there is a need for the production of such uninterruptible power supply with readily available and low cost components. Hence the main focus of this project is to design and construct a UPS by converting D. C. power into A.C. power using inverters.

Switching device are the simplest form of inverters and are used here because of their higher efficiency, smaller size and weight. There are other methods of converting D.C. Such as converting machinery like synchronous rotary converters, solid state converters, motor generator sets, etc.

The common application of inverters are:

  1. They are use to provide uninterruptible power supply to computers.
  2. Used in providing emergency lighting whenever there is power failure from the supply authority.
  3. Used in food processing industries where short interruption of power may spoil foodstuff.
  4. Used in speed control of induction motors.

1.1 History And Development Of Ups

The development of an uninterruptible power supply system paralleled the increase dependence of the society on electric power to provide motive power and intelligence for all aspects for modern life. These systems have become necessary since the 1920’s in areas of medical and telecommunication applications standby power supply systems set dates in 1920 with the work of Admiral Byrd which was extensively used in medical institutions. Gasoline and diesel engines was used during the world war II, as well as in microwave communication in 1955 and this was developed by N.B Tharp.

In the late 1950’s J.J Gano developed the storage battery for powering telephone central office, also the start of the computer age saw the development of the UPS using motor generator. In the area of modern UPS, the works scientist Dr. J.D. Standler and Engr. Libert whose works on the solid state UPS cannot be overlooked. Therefore as long as the need for the solution of the problem of public power failure continues, the need for the modification of the UPS will constantly continue.

1.2 Aims And Objectives Of The Project

The aim and objective of the design and construction of an uninterruptible power supply follows. Firstly, the primitive concern of providing quality and adequate power to sensitive devices like the medical faculties, data processing and communication centres.

Secondly, this work aim at the satisfaction of the statement of Alexander Kusko in his book Emergency/standby power system, that as the quest for the solution of the problem of public power failure continues, the need for the modification of the UPS will constantly be continued; by this we hereby aimed at modifying the already existing UPS.

Chapter Six

6.0 Design And Construction Of UPS

6.1 Assemblies Of All Sections Of The UPS



From the above section listed above, i.e

  • Rectifier/charger
  • Battery
  • Inverter
  • Inverter Circuit

All these listed section above forms the uninterruptible power supply (UPS) device.

6.2 Construction Of The Ups

6.2.1 Procedure

In the construction of the UPS, all components were mounted on a breadboard and the circuit was tested after ensuring that the circuit functioned well. The circuit was mounted on the breadboard to ensure its workability before soldering.

6.2.2 Construction On A Vero Board

After the circuit has be constructed and tested on the bread board and found to be working perfectly as desired. It was then transferred to the vero board and then soldered permanently.

6.3 Soldering Process

The soldering process was the most difficult process in achieving this project, as it was the most important factor to be considered to enable this project work efficiently. During this process all soldering techniques was observed to ensure that all components were properly soldered.

If efficiency of the circuit is required, the following factors has to be avoided.

  • Making dry joints
  • Excess solder
  • Damaging of components by applying too much heat etc.

In soldering, the soldering bit must be kept clean and free from oxides and dirts and the correct solder (lead used.

6.4 Conclusions And Recommendation

6.4.1 Economic Importance Application

The uninterruptible power supply has a wide range of application especially where unpredictable variation of voltage and frequency fluctuation adversely affect equipments. These applications include computer systems, telephone communication networks, industrial and household machines, etc.

Since electrical and electronics appliances are sensitive to voltage and frequency fluctuations, it is useful to feed them through network which smoothes out fluctuation in the supply and such network can be only supplied by the UPS device.

Apart from constancy of power supply, the UPS also protects equipments from the effects of power outage surge, sag, as well as spikes and bad harmonies, which are capable of damaging the device. The UPS also help in the smooth running of both industrial and household operations especially in production engineering, which requires constant power supply. The UPS also detects and absorb spikes which help in protecting devices like computer system from loss of memory. Finally since it changes overtime without lag, surge effects are highly protected thereby making it useful in telecommunication facility protection. Thus, the UPS is a good alternative power supply device.

6.4.2 Problem Encountered And Solution

During the design and construction of the UPS, we encountered little problems in the area of components used. Examples were the use of bipolar junction transistor, which initially dissipates more power thereby heating up the circuit rapidly which in turn burns the configuration. But this problem was solves by the replacement of the BJT with a MOSFET, which dissipates less power and has faster switching respond.

6.4.3 Conclusion

An uninterruptible power supply system has been successfully designed and constructed. The range of power output is 0 – 1000W. The project constructed was able to invert dc output from the battery when there was failure as the relay switches almost immediately to the battery bank and upon that the battery banks were being charged by the rectifier from an ac line when there was power supply. The power from NEPA was fed into the device and thus power is passed to the battery. The whole system depends on the battery when the energy in the battery is used up, the device backs up, due to this a need for a recharging circuit was made so as to replace the loss charges at all times.

The battery dc was passed through a transistor, which amplifies the dc signal. Due to the need for a.c line of 50Hz, an astable multivibrator oscillator or IC – type multivibrator oscillator was used to generate the required frequency.

The oscillator inverts the d.c to a.c and the inverted a.c is passed through power switching device. This switching element plays the role of driving the step-up transformer to give an amplifier output of 240V, 50Hz and an output of 1000W as required by the project.

The whole process is hinged on a multi-contact relay that automatically controls the whole system during power on from NEPA as well as power failure from NEPA. Thus, with these relays, when there is power failure from source, the device will automatically supply stored power from the battery to the load.

We hereby conclude that the designed work is still subject to modification, as we believed that any student willing to construct this type of circuit in future will still tremendously add to the modification of the work of UPS.

6.4.4 Recommendation

Comparing the designed work with the standby need of power supply, we hereby recommend that the duration for the operation of the uninterruptible power supply to load is normally short so as such, the need for a prolonging duration of supply can be enhanced by the use of external or larger battery bank or charge bank that will be able to supply power for a longer time.

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