ABSTRACT

The uninterruptible power supply (UPS) is design to help in the offices, workshops and house hold appliances, due to the unstable power supply being supplied by (NEPA) presently known as Power Holding Company of Nigeria (PHCN) usually supply to us.
With the help of the “UPS” we don’t need to depend much on PHCN it is stress free because it don’t need someone to change it over when light goes off, once there is any power failure it will automatically switched on and when power comes it will switch off and start charging the battery.
Another interesting thing in the UPS is that it does not need any external charger for charging the battery when it goes low, it have already built charger inside the UPS when there is light it will be charging the battery. 

CHAPTER ONE

 INTRODUCTION

Uninterruptible Power Supply (UPS) is used to continue the flow of current and also make voltage to be steady as soon as NEPA source is interrupted. They are divided into various sections, which are
1. INVERTER SECTION
In this section, the Direct Current (DC) voltage is converted into an Alternate Current (AC) voltage with the help of the oscillation. An oscillator is an electronic circuit that produces an output signal without any applied external input signal.

The inverter (Not Circuit) performs a basic logic function called inversion or complementation. The prupsoe of the inverter is to change on logic level (High/Low) to the opposite logic level. In terms of bits, it changes a ‘I’ to a ‘O’ and vise versa.

This section also consist of two stages of switching circuits which comprises of FIELD EFFECT TRANSISTORS.

The oscillator has two output terminals each of the switching circuits is coupled to the two output terminals of the oscillator respectively. This is elaborated in the subsequent chapter.

2. AUTOMATIC CONTROL SECTION
This section produces all the required controls needed to meet up with the main aim of the entire system. It controls automatically ‘ON’ of the system into NEPA and hence obtaining a NEPA line as the output of the system and same time linking battery charger into charging the battery. Also switching “ON” of the inverter into functional mode as soon as power interruption is experienced and this is done by the automatic circuit. This automatic circuit makes sure that no line is colliding by properly carrying out the exchange system with the help of the relays.

AIM OF THE DESIGN
The Uninterruptible Power Supply (UPS) provides the efficiency in the use of power appliance by ensuring continuous availability of power supply in the absence of NEPA source.

For a better output to be produced, it is advisable to charge the battery to its full condition and also make sure that the battery has enough ampere so as to withstand much load.

To eliminate excessive heat in the circuit, proper heat sink should be sued or a cooling fan, so as to reduce any heat that on the transistors.

The rated value for this UPS is 1000W at 240V and 50HZ. It is expected at all condition being favourable to carry load of higher power factor at approximation of the power stated. It can last for days depending on the load. It is advisable not to overload it because it can damage the circuit.