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CONSTRUCTION OF A DC/AC INVERTER
ABSTRACT
The DC/AC inverter consist of four (4) units. An input unit, two processing units, and an output unit. The input is a 12 volt DC battery while the output unit is a centre tap transformer with the ratio of secondary to primary turns as 1:10. The two processing units are an astable multivibrator and a class — B push — pull amplifier. All the units were connected on a Vero board using the soldering technique. When the 12V dc battery was connected to the processing unit a changing and amplified output waveform was produced which was then fed into the secondary winding of the centre tap step up transformer and the output signal was taken from the primary terminal. Upon testing, it was found that the ac output signal was about 240V.
CHAPTER ONE
INTRODUCTION
1.1 DC/AC POWER INVERTER
Anon (2011) defined a dc/ac power inverter as a device that converts direct current (dc), to an alternating current (ac). According to him, the ac obtained can be raised to any required voltage and frequency with the use of appropriate step up transformer, switching and control circuits.
Theraja and Theraja (2005) also define an inverter as a device that change a dc power into ac power. They stated that the inversion process can be achieved with the help of transistors which have advantages over Silicon controlled Rectifiers (SCR) inverters such as the switching speed, simplicity of control circuitry, high efficiency and greater reliability. This explain why SCR Inverters require complicated circuitry for triggering.
Anon (2011) briefly described the operational principle of the model Sl-17 SHP and Sl-400HP of an DC/AC inverter thus: the inverter works by first raising the dc voltage before converting it to ac voltage. He stated that the ac voltage provided by a household outlet is called “sine wave and the ac voltage that is produced by the inverter is referred to a quasi-sine wave’ or modified sine wave” This quasi- sine wave form is suitable for most ac power applications such as electronic appliances.
Thus, an inverter basically consists of an input, output and processing units. The input unit supply the required dc signal, the processing unit provide the frequency, period of oscillation and amplify the voltage signal while the output unit provides the ac output which can now be used to power our electronic devices.
Anon (2011) gave a brief history of an inverter as follows. The advert of an inverter can be traced to the nineteenth century through the middle of the twentieth century.
Dc to AC power conversion was accomplished using rotary converters, Vacuum tubes and gas filled tubes was then used as switching inverter circuits .The most widely used type of tube was the thyratron. He explained that the origin of electro mechanical inverters. Early ac to dc converter used an induction coil or synchronous dc motor directly connected to a generator (dynamo) so that the generator’s commutator reversed its’ connection at ‘exactly the right moments to produce dc. A later development is the synchronous converter in which the motor and generator windings are combined into one armature, with slip rings’ at one end and a commutator at the other and only one field frame with either ac in or dc out. Thus with an M-G set, the dc can be considered to be separately generated from the Ac. Hence given the right auxiliary and control equipment an M-G set or rotary converter can be run backward converting dc to ac. This shows that an inverter is an inverted converter.
1.2 STATEMENT OF THE PROBLEM
We all know that the major problem of our country over the years has been incessant power failure which has limited us as a people in all facets of our growth and development. The major reason for this development is because we have been over dependent on only one source of power generation which is the used of fossil fuels and gases. Thus, there is therefore the urgent need for us to diversify our source of power generation. This project provides an alternative means of generating electrical power which can serve the same purpose as the power generated from fossil fuels. This alternative method do not involve the burning of fossil fuels and gases which greatly contribute to the problem of global environmental pollution.
1.3 LIMITATIONS
The constructed circuit may not give a good performance compared to some standard ones in the market, because of the poor quality of the materials used for construction. The high cost of high quality materials made it impossible for them to be used for this work. For example, a high quality step up transformer will greatly increase the ac voltage output signal. Also, the soldering joints may introduce impurities which can affect the performance of the circuit.
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