Design And Construction Of A Dc To Ac Power Modified Sinewave Inverter Incorporated With Battery Charger

ABSTRACT

This project is on design and construction of a 1kva Modified sinewave inverter incorporated with its charger.

A power inverter, or inverter, is an electronic device or circuitry that changes direct current (DC) to alternating current (AC).

The input voltage, output voltage and frequency, and overall power handling, are dependent on the design of the specific device or circuitry.

A typical power inverter device or circuit will require a relatively stable DC power source capable of supplying enough current for the intended overall power handling of the inverter. Possible DC power sources include: rechargeable batteries, DC power supplies operating off of the power company line, and solar cells. The inverter does not produce any power, the power is provided by the DC source. The inverter translates the form of the power from direct current to an alternating current waveform.

The level of the needed input voltage depends entirely on the design and purpose of the inverter. In many smaller consumer and commercial inverters a 12V DC input is popular because of the wide availability of powerful rechargeable 12V lead acid batteries which can be used as the DC power source.

An inverter can produce square wave, modified sine wave, pulsed sine wave, or sine wave depending on circuit design.

The aim of this inverter is construct a 1kva modified sinewave inverter with an inbuilt automatic charger- which can charger an acid lead rechargeable battery and at same time turn-turn off the charger or stop charging the battery whenever the battery charge fully.

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 230v AC is obtainable.

This output voltage of 230v 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 emphasize 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. To this end, the equipment (DC-AC Converter) is incorporated to an impulse sealer machine which has about 3 sections where the,

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.

1.2                        OBJECTIVE OF THE STUDY

The objective of this project is to design and construct an inverter which is rated 1 KW which can be powered from the source of 12V battery which incorporated its battery charger.

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.

1.3               APPLICATION OF THE AN INVERTER

DC power source utilization

Inverter designed to provide 115 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. (See related: variable-frequency drive ) Switching states are developed for positive, negative and zero voltages as per the patterns given in the switching Table 1.The generated gate pulses are given to each switch in accordance with the developed pattern and thus the output is obtained. Thus the Simulink model and output voltage waveform of Symmetric multilevel inverter

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 9 V DC battery. First the 9VDC 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.

1.4    INVERTER RATINGS

The ratings that you should look at when buying an inverter (depending on the type) are:

1. Continuous Rating: This is the amount of power you could expect to use continuously without the inverter overheating and shutting down.
2. Half Hour Rating: This is handy as the continuous rating may be too low to run a high energy consumption power tool or appliance, however if the appliance was only to be used occasionally then the half hour rating may well suffice.
3. Surge Rating: A high surge is required to start some appliances and once running they may need considerably less power to keep functioning. The inverter must be able to hold its surge rating for at least 5 seconds. TVs and refrigerators are examples of items that require only relatively low power once running, but require a high surge to start.
4. IP rating – defines the ability of the inverter seals to prevent water and dust ingress. Although some inverter manufacturers claim high IP ratings suitable for outdoor installation, the quality and location of the seals and ventilation will greatly affect the ability of the inverter to outlast the many years solar installations are expected to work.
5. Peak efficiency– represents the highest efficiency that the inverter can achieve.

1.5 TYPES OF INVERTER

There are different types of inverters for home and industries available which can suit your various electricity needs. Following are the two basic types of inverters.

1. Modified Sine Wave Inverters

This type of home inverter obtains power from a battery of 12 volts and must be recharged using a generator or a solar panel. Appliances like microwave ovens, light bulbs, etc. can be run using these types of inverter.

• They can be rightly held as the best inverters for homes as they are efficient enough to provide power to the normal home requirement.
• They are the home inverters that are most affordable
• You can run the daily used home appliances using the modified sine wave home inverters.
• The electric appliances that involve motor speed controls or timers are not to be run using these types of home inverters.

The wave form of a modified sine wave inverter is as below:

2. True sine wave inverters

This is one of the better types of inverters as they provide better power as compared to the modified sine wave inverters for homes. These types of home inverter are also run using a battery of a larger capacity.

• Technically speaking, the sine waves they produce are purer, thus the
• They are best inverters employed for the power sensitive appliances like refrigerators, televisions, air conditioners, washing machines, etc.
• These types of inverters are extremely reliable. The only drawback is that they are a bit expensive and cannot be afforded by the common man.
• There are various models available based on the electricity requirement of the house.

The wave form of a sine wave inverter is as below:

3. Square wave inverter

This is the simplest form of output wave available in the cheapest form of inverters. They can run simple appliances without problem but much else. Square wave voltage can be easily generated using a simple oscillator. With the help of a transformer, the generated square wave voltage can be transformed into a value of 240VAC or higher.

The wave form of a square wave inverter is a below: