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Design and Construction of 2KVA AC/DC Inverter

1.0 Introduction
This project focuses on conversion of DC to AC power inverter whose aim is to
efficiently c...
1.1 Background Information and System Design
From the late 19th century to the middle of 20th century DC to AC conversio...
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Design and Construction of 2KVA AC/DC Inverter

  2. 2. 1 CHAPTER ONE 1.0 Introduction This project focuses on conversion of DC to AC power inverter whose aim is to efficiently convert a DC power source to high voltage AC source, similar to power that would be available at an electrical wall outlet. Inverters are used for many applications as in a situation where low voltage DC sources such as batteries solar panel or fuel cells must be converted so that devices can run on AC power. One example of such a situation is converting electrical power from a car battery to run a laptop, television, cell phones e.t.c. The method in which the low voltage DC power is inverted is completely in two steps. The first being the conversion of low voltage DC power to a high voltage DC source, and the second step is being the conversion of the high DC source to an AC waveform using PWM (Pulse Width Modulation). Another method to complete the desire outcome would be to first convert the low voltage DC power to AC and then use a transformer to step up the voltage to 220volts. However, due to the erratic power supply of electricity in Nigeria, an alternative means of power supply has to be incorporated to supplement the supply of electricity which one of such form of power is inverter.
  3. 3. 2 1.1 Background Information and System Design From the late 19th century to the middle of 20th century DC to AC conversion was accomplished using rotary converters, or motor generator (MG) set. In the early 20th century, vacuum tube and gas filled tube began to be used as switches in inverter circuit. The most widely use type of tube is thyraton. The origination of electromechanical inverters explains the source of the term inverter. Early AC to DC converters used on conduction of synchronous of AC motor direct connected to a generator (DYNAMO), so that the generator commutation reversed it connection exactly the right moment to produce DC. A later improvement is the synchronous converter, in which the generator and motor winding are combined into one armature which slip rings at one end and the commutation at the other end and only one field frame. The result is either with AC-on, DC-out. With an M.G set, the DC can be considered to be separately generated from the AC with a synchronous converter, in a certain sense, it can be considered to be mechanically rectified AC. Using the right auxiliary and control equipment, and motor generator set or rotary converter can “run backward”, converting DC to AC. Hence, an inverter is inverter converter. It should also be noted that early inverters did not use transistors for switching purposes, because its voltage and current ratings were not high enough for most inverter applications.
  4. 4. 3 However, in 1975, the silicon control rectifier (SCR) was introduced as switches, hence initiating a transition to solid state inverter circuits. Today, however due to an increased knowledge in technology, modern inverters are less bulky and more efficient with the use of various components such as ICs (Integrated Circuits) 1.2 Aims and objectives The main aim of this project is to design and construct a 2KVA inverter with 12volts supply so as to achieve the following objectives; i. To ensure the protection of the back-up source consumer equipment and supply. ii. To back-up the erratic power supply by PHCN. iii. To modify sine wave that can be used to power appliances both in houses and industries. iv. To safely operate any electronic devices (such as micro wave, speed motor) that require sensitive calibration. The design and construction of this project was to provide an ample chance for an understanding of the characteristics, operations, and application of power electronic devices. In addition, generally it gives an understanding of basic design concept of inverter based on MOSFET (Metallic Oxide Semiconductor Field Effect Transistor) switching and PWM (Pulse Width Modulator).
  5. 5. 4 1.3 Limitation The major limitation of this project is that it cannot operate equipment or an electronic device that is above its rated current due to some form of losses during the circuit operation.
  6. 6. 5 CHAPTER TWO 2.0 Literature Review In an inverter circuit, the DC power is connected to a transformer primary through the center tap of the primary windings. A switch is rapidly switched back and forth to allow current to flow following two alternate paths through one end of the primary winding and then the other end. The alternation of the direction of flow of current in the primary winding of the transformer produces an alternating current in the secondary winding. The electromechanical version of switching devices includes: two stationary contact and spring support moving contact. A power inverter converts DC power or direct current to standard AC power or alternating current, which facilitates the running electrical equipment of the car, home or office for mobile application, emergencies or simple convenience. The output voltage could be fixed or variable voltage and maintaining the DC gain of the inverter constant, on the other hand, if the DC input voltage is fixed, a variable output voltage can be obtained by varying the gain of the inverter, which is normally accomplished by PWM control within the inverter. Power inverters are great for camping at parks and picnics where electricity is not or rarely available. The toaster, blender, and printer can all still be used. In a utility outage, a power inverter can be used for emergency electricity. The radio can be plugged
  7. 7. 6 in to tune into important alerts, run essential medical equipment, lights or whatever electronic garget that falls within the inverter's power limits. 2.1 Review on early inverter In the effort in pursuit of the conversion of DC power to AC power has being since the late 19th century and from then to the middle 20thcentury;DC to AC power conversion was accomplished using rotary converter or motor generator set. In the early 20th century, vacuum tubes began to be used as switches in inverter circuit. First Generation of Inverter From the invention of inverters, a switching device is usually made use as a means to switch the transformer to ON/ OFF state in order to generate fast rate frequency. Silicon controlled rectifier (SCR) is an example of a switching solid electronics component adopted to ensure the switching of the system to ON/ OFF state at a considerable faster rate compared to a manual switching. SCR consist of three main terminals namely; Anode, Cathode and Gate. When two SCR are connected to a center tapped transformer, current will flow in positive half cycle (ON current) and negative half cycle (OFF current). This is the same as the application of Silicon Controlled Rectifier as full wave rectifier.
  8. 8. 7 Second Generation This generation made use of multivibrator, amplifier and transformer. The process takes input from 12VDC source, and runs from the supply to the multivibrator, and from the multivibrator to the amplifier, and finally to the transformer which gives AC voltage as output. This is inverted to a 240V AC, the multivibrator used may be bistable or astable which have two stage cycles useful for generating square waves and pulses. The 12V DC source serves as the power supply to the inverter. Third Generation In this generation, two 555 timer ICs were used for generating oscillations of equal frequency. An astable multivibrator is used to switch ON/ OFF, to generate constant frequency of 50Hz. The frequency generated by each 555 timer ICs is controlled by the input configuration of the RC circuit. The output from the ICs is amplified by drivers and then fed to the gate of the MOSFET. The NE555 timer IC was used to replace the first generation and second generation inverters due to some difficulties experienced and the inefficiency of its components.
  9. 9. 8 2.2 Basic Design Considerations Some design considerations were fulfilled in the process of designing this project; which was properly taken cognizance of, in order to meet the design objectives. A close look at these considerations would reveal that they all emphasize on obvious link between design and we, the designers. Formulating the right problem is one of the basic design considerations. It encompasses ensuring that the objective and requirements of the device, equipment, machine or facility are right to save-guard against possible failure. Designing an appropriate solution is one of the major factors to be considered in the course of the project design. It entails ensuring that the system is not only technically excellent but also appropriate and successful. A lot of work had been done on this project before finally arriving at the appropriate circuit to be used. 2.3 Review of Difference between Sine Wave and Modified Sine Wave The Sine Wave Inverter The electrical circuit of a pure sine wave inverter is far more complex than a square wave or modified sine wave inverter. Another way to obtain a sine output is to obtain a square wave output from a square wave inverter and then modify this output to achieve a pure sine wave. A pure sine wave inverter has several advantages over its previous two forms.
  10. 10. 9 More efficiency, hence consumes less power. They can be adjusted according to your personal power requirements, since several types are available with different power outputs. The output of a pure sine wave inverter is very reliable, but at the same time, there is a tradeoff between the price and reliability. Due to this reason they are the best option for sensitive equipment(fromwww.myprojectcircuit.com/2kva-inverter.htmledited). Figure 2.1 shows a pure sine wave The Modified Sine Wave Inverter The construction of this type of inverter is a bit more complex than a simple square wave inverter, but still it is a lot simpler than a pure sine wave inverter. A modified sine wave shows some pauses before the phase shifting of the wave, i.e. unlike a square it does not shift its phase abruptly from positive to negative, or unlike a sine
  11. 11. 10 wave, does not make a smooth transition from positive to negative, but takes brief pauses and then shifts its phase. Figure 2.2 showing the output waveform of a modified sine wave inverter 2.4 Safety of Inverter The only input to the inverter subsystem is from the battery, the battery is being charged from the power source (PHCN) through the charging subsystem through its integrated system. Our key concerns regarding the power inverter system were as follows: i. Safety - because we are dealing with high currents, many safety concerns needed to be accounted for. ii. Output Waveform
  12. 12. 11 iii. Power Output needs to handle at least 2000W iv. Efficiency generally there are a lot of losses associated with converting power. The inverter will receive DC power from the battery, and convert it to usable DC and AC outputs. All other subsystems receive information from the output of the power inverter. As such, the inverter is critical to the integrity of the entire system. Safety concerns must be at the forefront of the circuit design. These concerns stem to the safety of the users, as well as the circuitry itself. We recognized this issue, and accounted for it with properly placed kill-switches and fuses/circuit breakers. The circuit was designed so that if a power spike occurred, or something malfunctioned, the key components of the system would be saved, and the system would be shutdown.
  13. 13. 12 CHAPTER THREE 3.0 Methodology and Overall Design The construction was done by following the under listed procedures; Firstly, two sixteen IC socket were fixed on the Vero board to be used for panel construction. A 4.7k resistor was connected from pin 1of the first IC socket and then taken to pin 16 of the same socket. Two 0.1uf ceramic capacitors were connected in parallel and their joints are linked between pin 5 and 7. Pin 4 is also linked with pin 5 and both are grounded. Then 10k resistor is connected from pin 6 and then connected to another variable 10k resistor, the common path pin of this is linked with the second pin and the joint is grounded, two 4.7k resistors are connected to pin 1 and 2 and both are linked with pin 8 which is grounded. After this, pin 12 and 13 are joined together and both are connected to pin 15. This pin is then taken to the output pin of the used variable regulator LM7805, pin 10 is taken to the ground through a 4.7k resistor and also pin 9 is taken to the ground through a 10uf capacitor. A link is set between pin 14 of the first IC socket and pin 2 of the second IC socket, another link is set between pin 11 of the first socket and pin 4 of the second socket. These two links are both grounded through a 10k resistor, one for each link. Pin1 of the second IC is connected to pin 7 through a 10k resistor while another 10k resistor is used to link pin 2 and pin 7 at the socket. Pin 8 and pin 12 of the same IC are also
  14. 14. 13 connected together with another 10k resistor while 10uf capacitor is connected from pin 10 to the second socket and then to ground. A variable resistor is connected in such a way that its common pin is connected to pin 10 of the IC and the other two pins are connected such that one pin is grounded at the other end which receives the AC regulating signal from the control on the transformer to provide AC regulation for the AC output. Four transistors are connected to the Vero board such that the base of an NPN transistors are connected with the base of a PNP transistor, the emitter of NPN transistor is connected with the collector of the PNP transistor and these are taken to the positive pin of the used regulator. The base link is taken to pin 1 of the second IC through a 10k resistor. This process is repeated and it is connected to pin 3 of the second IC socket through another 10k resistor, then the collector of the NPN transistor and emitter of PNP transistor are linked together for each transistor arrangement, and this is linked with a 1k resistor which is looped with another 10k resistor that is grounded. The joint between the 1k resistor and the 10k resistor is tapped out for each transistor arrangement and each of these is taken to the gates of the MOSFET to be used must have been arranged on the heat sink. A limiting resistor is connected to these gates before they are connected to the joint point. The drains of the MOSFET are linked together with considerations given to how they are joined to the oscillatory panel. Each of
  15. 15. 14 these is tapped out which will be joined to end to end terminal of the secondary side of the transformer, while all the sources of the MOSFET are joined together to provide negative terminal connection for the inverter. 3.1 Block diagram of the system Fig. 3.1 Block diagram
  16. 16. 15 Circuit diagram of the system Fig. 3.1 Circuit diagram 3.2 Components of an Inverter One of the purposes of this chapter is to highlight the various components used in the construction of the circuits that makes up the project as well as outlining whatever calculation involved where necessary. The components making up the inverter include relays, resistors, capacitors, transistors, voltage regulators, heat sink, MOSFETs, switch and various ICs etc.
  17. 17. 16 Resistor The resistor is the most widely used circuit element. It offer opposition or introduces resistance to the flow of charges (electrons) or current in an electric circuit. They are placed to regulate the flow of current and voltage drop in both electrical and electronic circuits. In power circuits, they are used to reduce voltage by dissipating power. Figure 3.2 (a)Symbol of a resistor (b)physical appearance of a resistor Resistors are also characterized by how much power they can safely dissipate as well as other parameters such as tolerance, noise, temperature co-efficient, voltage co- efficient, stability with time and inductance. Capacitor The capacitor is another very important device that is essential in nearly every circuit application. It is passive circuit element. It is a device capable of storing electrical energy in the form of electrostatic energy. It consists of two plates separated by layer of insulating medium called a dielectric.
  18. 18. 17 The strength of the dielectric determines the capacity of the energy stored in the capacitor. The capacitance is the property of a capacitor to store electrical charges. Capacitors come in various sizes and shapes, and are named according to the type of insulation used. For instance, the ceramic capacitor used thin ceramic as its insulation, and the oil capacitor uses oil as its insulation. Fig. 3.3 (a) Symbol of a capacitor (b) physical appearance of capacitor Diode The diode is an electronic component which allows current to flow through it only in one direction thereby opposing the flow of current in the opposite direction. Other types of diodes used are Zener diode and light emitting diode.
  19. 19. 18 Figure 3.4 Symbol and physical appearance of a diode Relay An electromagnetic relay is basically a switch operated by a magnetic force. This magnetic force is generated by flow of current through a coil in the relay. Current flowing through the coil of the relay creates a magnetic field which attracts a level and changes the switch contacts. The coil current can be on or off, so relays have two switch positions and must have double throw (changeover) switch contacts. Figure 3.5 Physical appearance of a relay
  20. 20. 19 A relay basically consists of four parts: i. An electromagnetic made of a coil and a magnetic circuit ii. A movable armature iii. A set of contacts iv. A frame to mount all these components. Transistor The transistor is the most important example of an ‘active’ component, a device that can amplify, producing an output signal with more power in it than the input signal. The additional signal comes from an external source of power. In the inverter circuit, the transistor is used to generate oscillation signal amplification of signal and to switch on/ off various circuits. Fig.3.6 (a) Symbol of a transistor (b) Physical appearance of a transistor
  21. 21. 20 There are two types of standard transistors namely: the NPN and PNP transistors. These transistors consist of two PN junctions formed by sandwiching either P-type or N- type semi-conductors between a pair opposite types. Metal Oxide Semi-Conductor Field Effect Transistor (MOSFET) The MOSFET is a class of FET transistors. The FET as the name implies conduction in a channel is controlled to the gate electrode. There are no forward-biased junctions, so the gate draws no current. The MOSFET is an important semi- conductor device and is widely used in many circuit applications. In an inverter however, the MOSFETs are used as switching device at the inverter output section. The various terminal of MOSFET are; i. Source: This is terminal which majority carried enter the bar. Since carrier come from it, it is called the source. ii. Drain: This is terminal through which majority carrier leave the bar i.e. they are drained out from this terminal. The drain to source voltage V DS drives the drain current ID. iii. Gate: These are two internally connected heavily doped impurity regions, which form two P-N junctions. The gate - source voltage VGS reverse biases the gates.
  22. 22. 21 Figure 3.7 IRF3205 Physical appearance The MOSFET is used in the inverter circuit as a switching device due to the following reasons; i. It can work on very small drive power ii. Its efficiency is higher at the high frequency. iii. The input impedance of MOSFET is very high, so it can work without DC current. iv. Switching time of the ordinary transistor gets affected by temperature, whereas the temperature has very little effect on MOSFET device. v. The ‘safe operating area’ of the MOSFET is larger than the bipolar transistor; hence the MOSFET device does not get easily damaged.
  23. 23. 22 IRF 3205 The IRF3205 is N-channel MOSFET designed for high current switching applications. Rugged EAS capability and ultra-low RDS (ON) is suitable for PWM, load switching . Features i. VDS =55V; ID=105A@VGS=10V; RDS (ON) <6.0mΩ @ VGS=10V ii. Ultra Low On-Resistance iii. High UIS and UIS100% Test Application i. Hard Switched and High Frequency Circuits ii. Uninterruptible Power Supply Heat Sink This is a metallic component that is used to conduct away heat which is generated the MOSFET. It prevents the MOSFET from damage that may occur from overheating.
  24. 24. 23 Voltage Regulator A voltage regulator has only three legs and appears to be a comparatively simple device, but it is actually a very complex integrated circuit. A regulator converts varying input voltage and produces a constant regulated output voltage. Voltage regulators are available in a variety of outputs, basically 5volts, 9 volts and 12 volts. The last two digits in the name indicate the output voltage. Voltage regulators are very robust. They can withstand over-current draw due to short circuits. In both cases, the regulator will shut down before damage occurs. The only way to destroy a regulator is to apply reverse voltage to its input. This reversal of polarity can destroy the regulator almost instantly. To avoid this possibility, diode protection of the power supply is used. Generally, the input voltage should be limited to 2 to 3 volts above the output voltage. The LM7812 and LM7805 regulator is used for this project. Figure 3.8 (a) LM7805 physical appearance (b) LM7805 circuit diagram
  25. 25. 24 Transformer The transformer is a device that alternating current from one voltage level to another. It has no rotating parts. It works on the principle of mutual induction. Transformer needs two coils which is wound on a laminated core. These coils are called primary coil and secondary coil. The coil to which the AC supply is provided is called primary coil/winding while the coil in which the e.m.f is induced and from which the output is taken is called secondary coil/winding. There is no direct electrical connection between the primary and secondary coil in a transformer. Figure 3.9(a) transformer circuit diagram (b ) transformer diagram showing coils All transformers have the following essential elements; electrical windings insulated from each other and from the core, a core, and insulating materials.
  26. 26. 25 E.M.F. EQUATION OF A TRANSFORMER Let N 1 = number of turns in primary N 2 = number of turn in secondary Øm = maximum flux in the core, Wb = Bm x A where; Bm = maximum flux density in the core A = Area of the core f = frequency of A.C input, (in Hertz). Therefore; r.m.s value of e.m.f per turn = 1.11 x 4fØ max = 4.44fØ max volt Hence, r.m.s value of induced e.m.f in the whole of the primary winding is E1 = 4.44fØ max N1 …………………………………. (1) r.m.s value of induced e.m.f in secondary winding is E2 = 4.44fØmaxN2 ………………………………… (2)
  27. 27. 26 For an ideal transformer on no-load, V 1 = E1 and V 2 = E 2 Efficiency of a Transformer The efficiency of a transformer at a particular level and power factor is defined as the ratio of power output to power input. Therefore, efficiency can be calculated by determining core losses from open circuit test and copper losses from short circuit test. Losses in a Transformer The major losses in a transformer are power losses. The various kinds of losses are; core losses, copper losses, dielectric losses and stray losses. Integrated Circuit (IC) An integrated circuit as the name implies is a complete electronic circuit in which both active and passive components are fabricated on extremely single chip of silicon. Active components are those components which have the ability to produce gain e.g. transistors, while passive components are those components which do not have the ability to produce gain e.g. resistors, capacitor and inductors. Therefore, the integrated circuit is a discrete circuit which is built by connecting several components together. The integrated circuit is preferred in electrical/electronic circuits because it does the work of the entire components that are composed on it, and is handier and less bulky than using the components in it. In this project, we use SG3524IC.
  28. 28. 27 Figure 3.10 showing SG3524IC pin diagram Function of SG3524 IC This integrated circuit contains all the control circuitry for a regulating power supply inverter. Included in the 16-pin dual-in-line package is the voltage reference, error amplifier, oscillator, pulse width modulator, pulse steering flip-flop, dual alternating output switches and current limiting and shut down circuitry. This IC is a very common Integrated Circuit in MOSFET based inverter device. 3.3 Stages Involved in the Construction MOSFET Stage This stage consists of FET (Field Effect Transistor) which is arranged on the heat sink to ensure even distribution of heat on the transistor. The MOSFET is connected such
  29. 29. 28 that its gate before they are connected to the joint output. The drain of the MOSFET is linked together with consideration given to how they are joined to the oscillatory circuit. Each of this is tapped out with which will be joined to the end of the low voltage side of the transformer. All sources of the MOSFET are connected together and taken to the negative terminal of the battery. Figure 3.11 showing the MOSFET stage diagram Oscillatory Stage The oscillatory circuit is the stage of the inverter that produces frequency pulse which gets to the gate of the MOSFET drive after amplification. IC SG3524 is used as the oscillator of the inverter. The signal from pin 11 and pin 14 are connected to the
  30. 30. 29 second IC from where it is amplified and then taken to the MOSFET stage. The MOSFET drive signal is amplified. Figure 3.12 showing the oscillation stage diagram Battery Stage The battery is used to provide the required D.C to power the circuit, which voltage level was ensured to be 12V. SG3524N is a fixed frequency pulse width modulation voltage regulation control circuit. The regulator operates at the frequency that is programmable by the timing resistor, and one timing capacitor.
  31. 31. 30 Figure 3.13 showing deep cycle battery diagram Transformer stage The transformer consists of small AC voltage which is received from the MOSFET. It is transformed and stepped up to an appropriate value ranging from 220V to 240V depending on our desire which is varied from the 10k resistor to the IC SG3524. The transformer high voltage side serves as the inverter output to the socket, it also receives from power supply from PHCN and then used in charging the battery.
  32. 32. 31 Figure 3.14 showing the transformer stage diagram 3.4 How to choose the best inverter battery Nowadays, it is almost unimaginable to survive without power supply in our homes or workplaces. However, the moment power supply to our appliances and other gadgets that makes our everyday lives a lot easier and relaxed goes off, our lives becomes boring. Such situation leaves us really bothered unless there is an inverter with a powerful inverter battery. Here is a list of some most important things to consider when choosing the best inverter battery is as follows; i. Understand the power requirement ii. Be aware of the inverter battery size that you require. iii. Find the VA rating of the inverter you require. iv. Consider the bigger appliances
  33. 33. 32 CHAPTER 4 4.0 Test, Observation and Results The design of the project, construction of a 2KVA Inverter, was followed by its construction. Many considerations were put in place in form of procedures and instructions, which led to the successful completion of the project. The project is constructed on a Vero board, in which the size of the main panel board was used to choose the dimension of the casing used. 4.1 Testing Purpose of Testing Testing of components is important during construction to ensure that the works compiled together are perfect with their specifications. Testing is also essential during operation and after the completion of the construction made to determine the longevity of the inverter in order to detect common fault that may arise. There are sequences of test needed to undergo for any successful project. i. Component testing ii. System testing Component Testing Every component was tested singly to ensure that each was in good condition before assembling on the board. The major test carried out on these components was
  34. 34. 33 continuity testing done with the use of multi-meter like transistors. The test made on transistors was used to test each terminal of a transistor. Polarity testing was also performed on some components like diode, capacitors, etc. System Testing This involves the testing of the entire circuitry and thus, examine it for errors like short-circuits, lead flux, joining unwanted links. Proper insertion of IC pin layout and also checking if ICs of these pin number are slotted in their proper base. After checking, cross check again before powering the system. 4.2 Observation It was observed that components used for the construction are not predominantly static, electronic data book played a major role in identifying other available component in the absence of one. The first section that was carried out was the MOSFET arrangement which was tested and was found working. The second was the oscillating circuit while the third is the charging circuit. All the circuits were tested and found to be working. The MOSFET arrangement later developed some problems likewise the oscillating circuit, the problems were later resolved after consulting the supervisor and our senior colleagues.
  35. 35. 34 The MOSFETS stage The MOSFET used for this project is IRF3205 and the drain current rating of the MOSFET is 100A (at 250C). By considering increase in temperature (let say 1000C), the drain current rating is taken as 105A. This is because as the temperature increases, the drain current also increases. Therefore, the drain current is taken as 105A. Inverter power rating = 2KVA Input voltage = 12V Therefore, in order to determining the current that will flow in the input circuit: P = IV ∴ I = 𝑃 𝑉 Therefore, I = 2000VA 12V Therefore, I = 167A Oscillator Stage The frequency of oscillation is set to 50Hz. This is determined by the values of the charging resistor RA and RB, capacitor C1 and discharging resistor RB. To obtain approximately 50% duty cycle, the value of RA is set to 1kΩ.
  36. 36. 35 Figure 4.1 showing the circuit diagram of Astable Multi-vibrator Circuit using NE555IC The Transformer stage This is the final and output section of the inverter circuit is always step up transformer in order to increase the ac voltage generated. The transformer determines the power of the inverter. For our project (i.e. 2KVA inverter) a 12V/220V step up center- tap transformer was used. 4.3 Results The power rating of the inverter is 2KVA Therefore, at the input (primary side)
  37. 37. 36 V = 12V, P = 2000VA Therefore, I = 𝑃 𝑉 = 2000𝑉𝐴 12𝑉 I = 167A At the output (secondary side) V = 220V P = 2000VA I = 𝑃 𝑉 = 2000𝑉𝐴 220𝑉 I = 9.09A Inverter Output test After all stages had been coupled, the output of the inverter was tested. This was done by first connecting a voltmeter to the output terminal of the inverter to test the output voltage. A 200W bulb was then connected to the output terminal of the inverter to see if the bulb will bring light at a desired brightness. 4.4 Casing and Packaging A new casing was purchased, and also a cover board in order to produce a neat and durable production.
  38. 38. 37 We ensured that the casing purchased contains a ground wire to give it a proper earthing. Figure 4.2 Casing of the inverter 4.5 Assembling of Section The sections were assembled together in the casing properly and carefully to avoid destroying the circuit arrangements. We also ensured that the assembling does not create avenue or chance for short circuit and so, we connect the circuit to a ground wire. Assembling Instruction It is often easier while assembling the components on the board to erect them according to their height. That is, the lowest components first, usually the resistor and other tiny ones while others with higher height follow. Care was taken in getting the polarity of components like diode, electrolytic capacitor etc., before they were being
  39. 39. 38 soldered on the panel. Also, the biasing of the transistor was vividly ascertained before permanent soldering on the board was carried out. The use of IC socket was employed to avoid any damages that might result from excessive heat while soldering the IC. The pin configuration of the IC used and its connectivity with other components on the board were strictly adhered to as shown on the design work before the socket was permanently soldered. In fact, IC socket was the first item on the board while other components were placed around it. 4.6 Cost Analysis Table 4.1 below shows the cost expenses of the project; S/N DESCRIPTION PRICE 1. Components 10,900 2. Battery 45,000 3. Transportation 4,500 4. Transformer purchase 5,500 5. Casing expenses 6,300 6. Miscellaneous expenses 2500 TOTAL 79,200
  40. 40. 39 4.7 Troubleshooting/ Fault tracing This is a way of identifying, tracing and locating fault for immediate rectification. Problems may result from inadequate soldering and most likely be the reason why the circuit may not work. Other reasons may be due to electrical contact between the leads of the component, excessive voltage supply to the circuit (in case of using an adapter) etc. Soldered joints were carefully checked under bright light to ensure adequacy. All components were also checked to make sure they were in their correct position on the board. The voltmeter was used to check voltage at various points on the circuit was also embraced to follow the connection tract. 4.8 Maintenance and Repair Maintenance and repair of an inverter is tedious to carry out. It involves the technical know-how of an individual to put together his garnered experiences to properly handle the repair of an inverter. Nevertheless, some routine maintenance checks may be carried out for precautionary and safety measures. Some of this maintenance checks are: i. Check for proper ventilation in the inverter which is provided by the cooling fan. ii. Ensure proper charging of the battery to avoid overcharge of battery which may cause damage to the battery. iii. Battery terminal should be checked regularly to ensure proper supply to the inverter.
  41. 41. 40 Other maintenance and repair can also be carried out at the different stages of the inverter as this helps to detect faults that may arise and for it to be rectified immediately.
  42. 42. 41 CHAPTER FIVE 5.0 Conclusion This project has given us better understanding of the practical aspect of our course of study (Electrical/Electronic Engineering), it has also enable us to acquire more practical skill and knowledge. The completion of this project of construction of a 2KVA inverter with 12V DC dry cell battery has given expected results after different tests were carried out on each stage which gave durable and accurate results. The proper running of this inverter is a clear indication that the set aim and objectives have been achieved. The construction is based on the theoretical knowledge gained so far during our lecture times. It is constructed with considerable cost, available and reliable components rather than the more exorbitant unavailable ones. The practical knowledge of the multi–purpose use of SG3524 IC, MOSFETs, relay etc makes the project interesting, tasking and educating. 5.1 Recommendations Logically, irrespective of how good a design might be, there is always room for improvement. By so doing, the following recommendations could be taken into consideration for more effective and useful inverter.
  43. 43. 42 i. Competent personnel should be consulted in case of any damage to the unit and every source of power supply should be disconnected from the inverter before removing the cover. ii. Soldering of components should take a network system in order to minimize heat to the components. iii. On no occasion should the inverter be loaded above 80% of its maximum capacity. It’s an international advice. iv. Student should be exposed to more practical works so that they would be able to construct all practical works themselves. v. Government at various levels should encourage engineering practice by financing and training of engineering within and outside the country for the benefit of the students and the nation at large.
  44. 44. 43 REFERENCES Team Not Platypus (May 12, 2010) ‘DC-AC/DC Power Inverter’ Authors: Matthew Brown, Henry Godman, John Martinez, Dylan Paiton and Matthew Paiz Abdulwahab Olanrewaju Issa (2016) ‘Practical guides to project writing for students in Polytechnics, Colleges and Universities’ Department of Library and Information Science, The Federal Polytechnic, Offa, Kwara state. BL Theraja (2003) Principles of Electronics Kwaha, B. J., Iluonu, J and Danladi, C. (June 2004) ‘The design and construction of a 2kVA H-bridge inverter’ Department of Physics, University of Jos, Jos. https://www.exidecare.com/blog/battery-care/how-to-choose-the-best-inverter-battery
  45. 45. 44 Student final year project (April 2014) ‘Construction of 3KVA DC/AC Inverter with Deep cycle battery’ Authors: Azeez Akande, Olaniyan Kunle, Bello Oladayo, Ajimotokin Festus, Npue Collins Department of Electrical/ Electronics Engineering, Federal Polytechnic, Ede, Osun state. www.myprojectcircuit.com/2kva-inverter.html