Inverter is an uninterrupted power supply which conversed from D.C to AC voltage with the help of an oscillator. This inter section consist of two stages of switching circuits which comprises of a power transistor connected in the common emitter configuration. It is designed in such a way that it will take up 12v DC from battery and inverts it to an output of 220v, 50H2 AC. It makes no noise during operation and no hazardous carbon monoxide is generated in the surrounding.   This is a feature that makes it safe to use any where when compared to generator. Also, the circuit is capable of charging the battery (i.e 12v source) when the power from the supply authority is ON. This greatly reduces the cost of operation of the system. The trickling charger charged battery under no-load at a rate equal to its self-discharge rate, thus enabling the battery to remain at its fully charged level.

 

 

CHAPTER ONE
1.0                                                        INTRODUCTION
All modern engineering system include certain aspects of control systems at some point in their broadcast sense, control engineering and  the associated theory are concerned with the means by which systems may be made to behave an a desired way.
The system on this thesis is a DC – AC converter, which is an apparatus which is used for conversion of Direct Current to Alternating Current or signal.
In our country, this equipment is not all that in used not because it is not important but because people never give it a thought as per the construction and design.
It is meant, use with a 12v lead acid battery. If it’s in a car for example a suitable output voltage of 220v AC is obtainable.
This output voltage of 220v AC can be used for powering small electrical appliances such as light, electric fans, radio, soldering iron etc.
However, it is worthwhile that AC operated with this appliance is nothing comparable to the AC generated by big generators. This is so because the voltage and power are less in terms of AC generation duration. This appliance is therefore suitable for short time replacement for the real AC generation especially in the remote areas and install where electrical appliances are sold and the need might arise for it to be tested and certified good.
Another main area where this equipment can be of great utility is in communication system, in a situation where there is constant AC power supply failure e.g in offices, DC – AC converter is need and in such cases can be used as a light sources.
Most industries in the country do not make use of DC – AC converter because they are thought to be costly with respect to the task they perform. However, putting into consideration the task this appliance can be used for, it can be concluded that it is cheaper. The construction is simple, cheaper easy to operate and portable. The usefulness of this device and the function cannot to be over emphasizing now in our economic situation and also when our power generating authority (NEPA) has been dubbed NEVER EXPECT POWER ALWAYS.
In these times when control and monitor a complex field engineering operations have gone computer based a failure of AC power supply to communication equipment means work stoppage and to some small scale industries a lot of economic and material losses avoidable.
First stage is of the dimmer switch with regulates, the rate at which the power flow is needed. The second stage being the main switch(s) which controls the primary side, secondary side of the transformer, the stage 3 comprise of the element made of construction wire which does or finishes the work needed for the machine. Most essential circuit in this device:
TRANSFORMER: This has two parts, this is the secondary part which is the output and it produces 220 – 240 volts. The second part of it is the primary part which is the input. It has 12 volts.
OSCILLATOR:          This circuit is with the integrated circuit (IC) 4047. It has a variable resistor of look and the work of this valuable resistor is to reduce or increase the frequency of the oscillator.  The oscillator produces square wave form within two channels to two transistors which are the pre – amp driver.

THE AUTOMATIC CONTROL UNIT: These control units produce all the controls that is needed to make up the aim of the entire system. These controls like “ON” the inverter into production as soon as NEPA interrupter is expanded. This circuit ensures that, there is no line jamming is to be encounter by carrying out the exchange system property.
CHARGING SYSTEM:  In this system, there are two AC relay which has the current rating of 40 Amp each. In the relay, here is also normal open and normal close, the number is terminal which is the normal close is connected to the positive terminal. The relay act as the switch of the charging system with a circuit of trickle charging system which act as the protector of the battery with a CMOS 1.C (Compreminary Mineral Oxide Semi - Conductor) and two transistor which act as the battery level indicator.

1.2                                    OBJECTIVE OF THE PROJECT
The objective of this project is to design and construct an inverter which can be powered from the source of 12V battery which incorporated its battery charger. The battery charger is used to charge 12 volts battery. This inverter is capable of operating a wide variety of loads; electronic and household items including but not limited to TV, VCR, and satellite receiver, computers, and printers.

Specific objectives of this project are as follows:
1.         To design and construct a circuit that converts dc power to an ac power for various appliances used in laboratories, theatres and rural areas that is rated 1.5kva.
2.         To provide a noiseless source of electricity generation and also power with low maintenance cost and zero fuel cost
3.         To have a source of generating electricity that has no negative effect on the environment.
4.         To design an automatic battery charging system capable of recharging the battery source when it goes below a threshold value 0f 11V.
5.         To design a  frequency control circuit that maintains the operation frequency at 50hz even when the frequency tends to shift as a result of low battery.

1.3                                         SIGNIFICANCE OF THE PROJECT

• high quality and inexpensive; using modified square wave; output correction waveform; relatively stable; suitable for ordinary personal users with TV, fan, lamp, computer, hot pot
• The efficiency of an AC is enhanced since the start/stop cycles are eliminated in a DC Inverter AC. The AC does not operate at full power, but still maintains the desired temperature. This is another reason why these ACs can still save energy even if there are regular power outages.
• Inverter ACs is cheaper to operate in almost all types of conditions.
• Quicker cooling or heating (based on feature availability) can be achieved since an inverter AC can pull the required current on its own to increase initial cooling or heating. The inverter AC can calculate the current draw by using the indoor and outdoor temperature difference.
• DC Inverter ACs don’t put extra load on its power supply. Therefore you don’t see fluctuations in electricity caused by them.
• The life of components (used in the AC and other electrical household components) is increased due to the same reason i.e. gentle power draw.
• DC Inverter ACs are much quieter compared to conventional ones. The outdoor unit usually makes far less sound as the unit is operating at a reduced rate.
• Also, the inverter circuit is capable of charging the battery (i.e 12v source) when the power from the supply authority is ON. This greatly reduces the cost of operation of the system. The trickling charger charged battery under no-load at a rate equal to its self-discharge rate, thus enabling the battery to remain at its fully charged level.

1.4                                PROBLEM/ LIMITATION OF THE PROJECT

• Lack of power, cannot run the appliances with same power labeled; it’s easy to damage the machine if customers are not familiar with the operation, the user needs to strictly follow the manufacturers’ instructions.
• DC Inverter ACs cost more. Even without the dual-mode function, they still come with high price tags.
• Repair costs increase as components are more sophisticated and as a result, more expensive. They require more effort to build or repair.
• Response Time: The inverter shall respond to any line voltage variation in 1/2 cycle while operating linear or non-linear loads, with a load power factor of 0.60 of unity. Peak detection of the voltage sine wave shall not be permitted to avoid inaccurate tap switching due to input voltage distortion.
• Operating Frequency: The inverter shall be capable of operating at +10% to -15% of the nominal frequency, 50Hz.
• Rating: this device shall be rated at kVA.
• Access Requirements: The inverter shall have removable panels on the front, rear and sides as required for ease of maintenance and/or repair.
• Metering: An input meter is provided to display line voltages.
• Ventilation: The inverter isolation transformer shall be designed for convection cooling. If fan cooling is required for the MOSFET used.

1.5                                                 SCOPE OF THE PROJECT
A power inverter changes direct current (DC) to alternating current (AC). The input voltage, output voltage and frequency, and overall power handling depend on the design of the specific device or circuitry.
Inverter takes current from a battery, which is usually 12 Volt Dc, as batteries usually produce DC power, and then after passing this current through a 50Hz processor, it converts it into the normal 220 volt Ac which is commonly used.
Also, the circuit is capable of charging the battery (i.e 12v source) when the power from the supply authority is ON. This greatly reduces the cost of operation of the system. The trickling charger charged battery under no-load at a rate equal to its self-discharge rate, thus enabling the battery to remain at its fully charged level. Also the power supply of the trickling battery charging system depends on the transformer of the inverter – this means, it does not have separate transformer to charge the battery and or to power the battery.

1.6                                                     TYPES OF INVERTER
Inverters can be categorized the following ways:

• Stand-alone (also known as Off-Grid): Used in isolated systems where the inverter draws its DC energy from batteries charged by solar arrays and/or other sources, such as wind turbines, hydro turbines etc.  Normally these do not interface in any way with the utility grid, and as such are not required to have anti-islanding protection.
• Grid-Tied: These systems match their phase with a utility-supplied sine wave.  Grid-tie inverters are designed to shut down automatically upon loss of utility supply (referred to as anti-islanding protection).  They do not provide backup power during utility outages.
• Battery Backup: These are special inverters which are designed to draw enrgy from a battery, manage the battery charge via an onboard charger, and export excess energy to the utility grid.  These inverters are capable of supplying AC energy to selected loads during a utility outage, and are required to have anti-islanding protection.

1.7                                          APPLICATION OF THE PROJECT
Inverters find diverse uses and applications in daily life, due to their function of converting DC to AC. The applications are as follows:
DC power source utilization
Inverter designed to provide 220 VAC from the 12 VDC source provided in an automobile. The unit shown provides up to 1.2 amperes of alternating current, or enough to power two sixty watt light bulbs.
An inverter converts the DC electricity from sources such as batteries or fuel cells to AC electricity. The electricity can be at any required voltage; in particular it can operate AC equipment designed for mains operation, or rectified to produce DC at any desired voltage.
Uninterruptible power supplies
An uninterruptible power supply (UPS) uses batteries and an inverter to supply AC power when main power is not available. When main power is restored, a rectifier supplies DC power to recharge the batteries.
Electric motor speed control
Inverter circuits designed to produce a variable output voltage range are often used within motor speed controllers. The DC power for the inverter section can be derived from a normal AC wall outlet or some other source. Control and feedback circuitry is used to adjust the final output of the inverter section which will ultimately determine the speed of the motor operating under its mechanical load. Motor speed control needs are numerous and include things like: industrial motor driven equipment, electric vehicles, rail transport systems, and power tools. Switching states are developed for positive, negative and zero voltages as per the patterns.
Power grid
Grid-tied inverters are designed to feed into the electric power distribution system. They transfer synchronously with the line and have as little harmonic content as possible. They also need a means of detecting the presence of utility power for safety reasons, so as not to continue to dangerously feed power to the grid during a power outage. The subsystem which includes sinusoidal and triangular subsystem brief about the comparison of sine wave which is the modulated signal and is compared with carrier signal. When the reference signal is greater than or equal to carrier signal, then the output waveform is above the reference and otherwise it will be below the reference
Solar
A solar inverter can be fed into a commercial electrical grid or used by an off-grid electrical network. Solar inverters have special functions adapted for use with photovoltaic arrays, including maximum power point tracking and anti-islanding protection. Micro-inverters convert direct current from individual solar panels into alternating current for the electric grid. They are grid tie designs by default.
Induction heating
Inverters convert low frequency main AC power to higher frequency for use in induction heating. To do this, AC power is first rectified to provide DC power. The inverter then changes the DC power to high frequency AC power. Due to the reduction in the number of DC Sources employed the structure become more reliable and the output voltage has higher resolution due to increase in the number of steps and the reference sinusoidal voltage can be better achieved. This configuration recently becomes very popular in AC power supply and adjustable speed drive applications. This new inverter can avoid extra clamping diodes or voltage balancing capacitors There are three kinds of level shifted modulation techniques, namely;
Phase Opposition Disposition (POD)
Alternative Phase Opposition Disposition (APOD) Phase Disposition (PD)
HVDC power transmission
With HVDC power transmission, AC power is rectified and high voltage DC power is transmitted to another location. At the receiving location, an inverter in a static inverter plant converts the power back to AC. The inverter must be synchronized with grid frequency and phase and minimize harmonic generation.
Electroshock weapons
Electroshock weapons and tasers have a DC/AC inverter to generate several tens of thousands of V AC out of a small 12V DC battery. First the 12VDC is converted to 400–2000V AC with a compact high frequency transformer, which is then rectified and temporarily stored in a high voltage capacitor until a pre-set threshold voltage is reached. When the threshold (set by way of an airgap or TRIAC) is reached, the capacitor dumps its entire load into a pulse transformer which then steps it up to its final output voltage of 20–60 kV. A variant of the principle is also used in electronic flash and bug zappers, though they rely on a capacitor-based voltage multiplier to achieve their high voltage.

REFERENCE

• Barnes, Malcolm (2003). Practical variable speed drives and power electronics. Oxford: Newnes. p. 97. ISBN 0080473911.
• James, Hahn. "Modifi ed Sine-Wave Inverter Enhanced". Power Electronics.
• George Wood Vinal (December 1955). Storage batteries: a general treatise on the physics and chemistry of secondary batteries and their engineering applications. Wiley. Retrieved 12 January 2012.
• InfoWorld Media Group, Inc. (28 August 1989). InfoWorld. InfoWorld Media Group, Inc. p. 29. ISSN 0199-6649. Retrieved 12 January 2012.
• Henk Jan Bergveld; Wanda S. Kruijt; Peter H. L. Notten (1 November 2002). Battery management systems: design by modelling. Springer. p. 171. ISBN 978-1-4020-0832-0. Retrieved 12 January 2012.

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