The Design And Construction Of A MOSFET-Based Power Inverter (PDF/DOC)
ABSTRACT
This project is titled the design and construction of a MOSFET power inverter system. It is designed to meet up with the power demand in the offices and in homes in the absence of power supply from the national power grid. In order words the device / item serves as a substitute for PHCN which almost monopolies the power supply to people.
It is designed in such a way that it will take up 12v DC from battery and inverts it to an output of 220v, 50Hz 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 aim of this work is build an inverter system that uses MOSFET as the switching device.
TABLE OF CONTENTS
COVER PAGE
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWELDGEMENT
ABSTRACT
CHAPTER ONE
1.1 INTRODUCTION
1.2 AIM OF THE PROJECT
1.3 OBJECTIVE OF THE PROJECT
1.4 SIGNIFICANCE OF THE PROJECT
1.5 SCOPE OF THE PROJECT
1.6 LIMITATION OF THE PROJECT
1.7 APPLICATION OF THE PROJECT
1.8 DIFFERENCE BETWEEN CONVENTIONAL GENERATOR AND INVERTER
CHAPTER TWO
LITERATURE REVIEW
- HISTORICAL BACKGROUND OF AN INVERTER
- REVIEW OF HOW TO CHOOSING THE RIGHT INVERTER
2.3 REVIEW OF THE DIFFERENCE BETWEEN SINE WAVE AND MODIFIED SINE WAVE INVERTER
2.4 REVIEW OF INVERTER CAPACITY
2.5 SAFETY OF INVERTER
2.6 TYPES OF INVERTER
2.7 IGBTS VS. POWER MOSFETS
2.8 ENHANCED N-CHANNEL VS ENHANCED P-CHANNEL MOSFETS
2.9 MOSFETS CHARACTERISTIC
2.10 MOSFET DRIVER
CHAPTER THREE
3.0 CONSTRUCTION
3.1 BASIC DESIGNS OF AN INVERTER
3.2 BLOCK DIAGRAM
3.3 3KVA MODIFIED SINE WAVE INVERTER CIRCUIT USING IC 3525, WITH REGULATED OUTPUT AND LOW BATTERY PROTECTION
3.4 PARTS LIST
3.5 DESCRIPTION OF COMPONENTS USED
3.6 HOW TO CHOOSE THE BEST INVERTER BATTERY
CHAPTER FOUR
4.1 RESULT ANALYSIS
4.2 CONSTRUCTION PROCEDURE AND TESTING
4.3 CASING AND PACKAGING
4.4 ASSEMBLING OF SECTIONS
4.5 TESTING OF SYSTEM OPERATION
4.6 RESULT ANALYSIS
4.7 MOUNTING PROCEDURE
4.8 TESTING OF SYSTEM OPERATION
4.9 TESTING OF MOSFET
4.10 DEAD MOSFETS
4.11 FREQUENCY STABILITY
4.12 OPERATING TEMPERATURE
4.13 EFFICIENCY
CHAPTER FIVE
- CONCLUSION
- RECOMMENDATION
- REFERENCES
CHAPTER ONE
1.0 INTRODUCTION
A power inverter is a device that converts DC power (also known as direct current), to standard AC power (alternating current). Inverters are used to operate electrical equipment from the power produced by a car or boat battery or renewable energy sources, like solar panels or wind turbines. DC power is what batteries store, while AC power is what most electrical appliances need to run so an inverter is necessary to convert the power into a usable form. For example, when a cell phone is plugged into a car cigarette lighter to recharge, it supplies DC power; this must be converted to the required AC power by a power inverter to charge the phone.
In modified sine wave, The waveform in commercially available modified-sine-wave inverters is a square wave with a pause before the polarity transition, which only needs to cycle through a three-position switch that outputs forward, off, and reverse output at the pre-determined frequency. The peak voltage to RMS voltage does not maintain the same relationship as for a sine wave. The DC bus voltage may be actively regulated or the “on” and “off” times can be modified to maintain the same RMS value output up to the DC bus voltage to compensate for DC bus voltage variation.
The ratio of on to off time can be adjusted to vary the RMS voltage while maintaining a constant frequency with a technique called PWM. Harmonic spectrum in the output depends on the width of the pulses and the modulation frequency. When operating induction motors, voltage harmonics is not of great concern, however harmonic distortion in the current waveform introduces additional heating, and can produce pulsating torques.
Most AC motors will run on MSW inverters with an efficiency reduction of about 20% due to the harmonic content.
1.1 AIM OF THE PROJECT
the main aim of this work is to build an inverter that uses MOSFETs as the switching device. MOSFETS in an inverter are the output devices that generate the ac voltage at the rated current. These MOSFETS are switched on/off by the pulse width modulation (pwm).
- OBJECTIVE OF THE PROJECT
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. At the end of this work, the student will be able to
i. Design a circuit for power inverter system.
- understand different types of inverter system.
iii. pin-out connections of MOSFET
1.2 SIGNIFICANCE OF THE PROJECT
In the recent years, power inverter has become a major power source due to its environmental and economic benefits and proven reliability. Since the power inverter system does not have moving parts, virtually it does not require any kind of maintenance once installed.
Power inverter is produced by connecting the device on the 12VDC battery as the input to produce 220VAC as the required output. It can also be connected to solar panel. Second, the whole energy conversion process is environmentally friendly. It produces no noise, harmful emissions or polluting gases. The burning of natural resources for energy can create smoke, cause acid rain and pollute water and air. Carbon dioxide, CO2, a leading greenhouse gas, is also produced in the case of burning fuels. Power inverter uses only the power of the battery as its fuel. It creates no harmful by-product and contributes actively to the reduction of global warming. In this work, MOSFET are used because: i Efficient switching, ii. Voltage drop, iii. smaller than BJTs. iv. No continuous gate current.
Inverters use MOSFETs with a Vds of around 100V and an Rds(on) that is as low as possible, usually in the tens of milliohms.
1.3 SCOPE OF THE PROJECT
A power inverter is a power conversion device. It converts fixed direct current (DC) voltage to frequency sinusoidal alternating current (AC) voltage output.
The use of inverter has become prevalent in wide range of industrial applications; from motion control applications to ventilation systems, waste water processing facilities to machining areas, and many others. Though power inverters offer lower operating costs and higher efficiency, they are not without their problems. MOSFETs used in this work are used for the switching operation. These MOSFETs or Transistors are connected to the primary winding of the inverter transformer. When these switching devices receive the MOS drive signal from the driver circuit, they start switching between ON & OFF states at a rate of 50 Hz. This switching action of the MOSFETs or Transistors cause a 50Hz current to the primary of the inverter transformer. This results in a 220V AC at the secondary of the inverter transformer. This secondary voltage is made available at the output socket of the inverter by a changeover relay.
1.4 LIMITATION OF THE PROJECT
- Expensive when compared to traditional generators
- There is no larger capacity inverter in the markets compared to power generators.
- The inverter can power a few appliances for a short period
- The input is limited to 12VDC, output to 240VAC and the frequency to 50Hz
- The wave form is modified sine wave.
1.5 APPLICATION OF THE PROJECT
the applications and uses of a power inverter which are as follows:
DC power source utilization
Inverter designed to provide 240 VAC from the 12 VDC source provided in an automobile. The unit shown provides more than 20 amperes of alternating current, or enough to power more than 1KW load. An inverter converts the DC electricity from sources such as batteries, solar panels, 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.
Induction heating
Modified Sine wave 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.
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.
Variable-frequency drives
A variable-frequency drive controls the operating speed of an AC motor by controlling the frequency and voltage of the power supplied to the motor. An inverter provides the controlled power. In most cases, the variable-frequency drive includes a rectifier so that DC power for the inverter can be provided from main AC power. Since an inverter is the key component, variable-frequency drives are sometimes called inverter drives or just inverters.
Electric vehicle drives
Adjustable speed motor control inverters are currently used to power the traction motors in some electric and diesel-electric rail vehicles as well as some battery electric vehicles and hybrid electric highway vehicles.
Air conditioning
An inverter air conditioner uses a variable-frequency drive to control the speed of the motor and thus the compressor.
Electroshock weapons
Electroshock weapons and tasters have a DC/AC inverter to generate several tens of thousands of V AC out of a small 12V DC battery.
1.8 DIFFERENCE BETWEEN CONVENTIONAL GENERATOR AND INVERTER
| CONVENTIONAL GENERATOR | INVERTER GENERATOR |
| Conventional generators have been around for quite a while, and the basic concept behind them has remained essentially unchanged. They consist of an energy source, usually a fossil fuel such as diesel, propane or gasoline, which powers a motor attached to an alternator that produces electricity. The motor must run at a constant speed (usually 3600 rpm) to produce the standard current that most household uses require (in Nigeria, typically 220 Volts AC @ 50 Hertz). If the engine’s rpm fluctuates, so will the frequency (Hertz) of electrical output. | Inverter generators are a relatively recent development, made possible by advanced electronic circuitry. It inverter draws power from a fixed DC source (typically a comparatively fixed source like a car battery or a solar panel), and uses electronic circuitry to “invert” the DC power into the AC power. The converted AC can be at any required voltage and frequency with the use of appropriate equipment, but for consumer-level applications in Nigeria, the most common combination is probably taking the 12V DC power from car, boat or RV batteries and making it into the 220V AC power required for most everyday uses. |
| Conventional generators always bigger and heavier than inverter | The compact size, relatively light weight and resulting portability of inverter generators make them the clear winner in this category. |
| Conventional generators always noisy | Inverter generators are often designed from the ground up to be comparatively quiet |
| Conventional generators are often designed simply to get a certain amount of power where it is needed, and to keep the power on. Factors like the size of the unit have not been a major consideration. This has meant that conventional designs can often accommodate sizeable fuel tanks, with the obvious result being relatively long run times. This means that it uses fuel for it to operate. | Inverter generator draws power from DC source, either from battery or solar panel. |
| Conventional generators emit smoke which causes pollution | Inverter produces no smoke |
| A conventional generator is nothing more than an engine connected to an alternator and run at a speed that produces the desired AC frequency, regardless of the load on it (as the load increases the engine throttles up to keep the engine speed the same). The output of the alternator is connected directly to the load, without any processing. | With an inverter generator, a rectifier is used to convert the AC power to DC and capacitors are used to smooth it out to a certain degree. The DC power is then “inverted” back into clean AC power of the desired frequency and voltage |
| Many inverters can be paired with another identical unit to double your power capacity. This type of parallel capability means you can use two smaller, lighter generators to provide the same wattage and amperage of one much larger generator – without sacrificing all the benefits of the smaller, lighter, quieter, more portable inverter units. | Conventional units simply can’t offer this feature. Note that you will need a special cable to connect your generators, which is generally not |
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