How an Inverter WorksSo how can an inverter give us a high voltage alternating current from a low voltage direct current.Let's first consider how an alternator produces an alternating current. In its simplest form, an alternator would have a coil of wire with a rotating magnet close to it. As one pole of the magnet approaches the coil, a current will be produced in the coil. This current will grow to a maximum as the magnet passes close to the coil, dying down as the magnetic pole moves further away. However when the opposite pole of the magnet approaches the coil, the current induced in the coil will flow in opposite direction.As this process is repeated by the continual rotation of the magnet, an alternating current is produced.

Now lets consider what a transformer does. A transformer also causes an electric current to be induced in a coil, but this time, the changing magnetic field is produced by another coil having an alternating current flowing through it. Any coil with an electric current flowing through it will act like a magnet and produce a magnetic field. If the direction of the current changes then the Polarity of field changes. Now, the handy thing about a transformer is that, the voltage produced in the secondary coil is not necessarily the same as that applied to the primary coil. If the secondary coil is twice the size (has twice the number of turns) of the primary coil, the secondary voltage will be twice that of the voltage applied to the primary coil. We can effectively produce whatever voltage we want byvarying the size of coil. If we connected a direct current from a battery to the primary coil it would not induce a current in the secondary as the magnetic field would not be changing. However, if we can make that direct current effectively change direction repeatedly, then we have a very basic inverter. This inverter would produce a square wave output as the current would be changing direction suddenly.This type of inverter might have been used in early car radios that needed to take 12 volts available in the car and produce the higher voltages required to run radio valves (known as in America ) in the days before transistors were widely used in the tubes.

A more sophisticated inverter would use transistors to switch the current. The switching transistors are likely to be switching a small current which is then amplified by further transistor circuitry. This will still be a square wave inverter.

The Sine Wave InverterTo get a sinusoidal alternating current from the output of our transformer, we have to apply a sinusoidal current to the input. For this we need an oscillatorAn amplifying transistor can be made to oscillate by feeding some of the amplified output back to its input as positive feedback. We will all have heard this effect at sometime when someone is setting up a PA or microphone system. If the microphone is too close to the speaker, some of the output from the speaker is fed back to the microphone and inputted to the amplifier again. The positive feedback in an electronic circuit can be tuned using extra components to produce the frequency we require (generally either 50 or 60 cycles per second to mimic mains electricity). If a crystal is used to control this frequency, as in a battery watch or clock, the frequency can be very accurately controlledAs with simpler switching transistor circuit, the oscillator will be producing a low current output. This will then need to be amplified by what will be roughly equivalent to a powerful audio amplifier to produce the high current for the primary coil of the transformer (the frequency of mains AC current is roughly equivalent to the lowest notes on a bass guitar).The transformer, while being very useful, does not do something for nothing. While increasing the voltage, the current will be reduced, and the power (voltage x current) will stay the same (less any inefficiency of the transformer). In other words, to get 1Kw of high voltage AC current out, you have put 1Kw of low voltage AC current in.

Grid Tied InvertersIf the above example were a grid tied inverter, ie able to feed power back into the national grid, it would need to use a sample of the mains voltage to then be amplified within the inverter, or to synchronize the oscillator with that sample.Grid tied inverters will also sense if there is a "power cut" and disconnect themselves from the grid. If they did not have this facility, in the event of a power cut, your inverter would be attempting to power all your neighbours houses and would present an electrocution risk to anyone working on power lines that had supposedly been turned off.The Main Inverter Types1. Square wave or modified sine wave.2. Sine wave (sometimes described as "Pure Sine wave")3. Grid-TiedSquare Wave or Modified Sine waveThe square wave form will be as shown above right and the modified sine wave form will have had some attempt to round the corners off though will still have some sharp corners or spikes.

Compare this to the Sine wave form below right.

Many AC appliances will work perfectly well a modified sine wave form wave.Some appliances such as computers, televisions, radios or music centres have in built power supplies that reduce the voltage, rectify it to produce a DC current, and smooth it to give a steady DCvoltage.This process will often smooth out any spikyness that was in the original AC supply.However, any inductive load (one where the power passes through a coil, as in a power supply transformer or a motor) causes the voltage and current to be out of phase (their appropriate graphs do not line up). Modified signwave inverters do not cope with this so well, causing the appliance to use more power than it would otherwise. This extra power consumption will cause the motor or transformer to run hotter than it would otherwise and may reduce it's life.It will also mean that the inverter will need a slightly higher power rating to power the same appliance.

There is also the possibility that your television picture may not be as good as it should and anything with a timer (eg bread maker) may not run at the correct speed.

There may also be a noise problem. Any equipment that may give a quiet hum when connected to the mains supply, is likely to give a more annoying buzz. My own experience has shown this to be true with a ceiling fan, particularly when running on the lower speeds.These potential problems will need to be balanced against the price difference (modified sine wave converters will be significantly cheaper than pure sine wave) taking into account the appliances you expect to be using.Grid-TiedA Grid-Tied inverter is capable of synchronising with an existing mains electricity supply (synchronising its sine wave output so that it is at the peak voltage point at the same time as the mains supply). This type of inverter can be used (where your electricity utility company allows it and with a modified meter if required) to enable you to push your spare electricity into the grid system. In some cases your normal electricity meter will simply run backwards when you are supplying power.A grid tied inverter designed to be used without a battery (and therefore no charge controller), may haveMPPTtechnolology built into it's input circuitry.String InvertersInverter designed to accept high input voltages (upto 600 volts in commercial systems) may be called String Inverters, refering to the series connected panels, used to produce the higher voltages, being connect as a string.DC Input VoltageYou may already have the rest of your system setup and you are already committed to using a particular voltage. You may however still be able to choose.The lower the input voltage you are using, the higher the current you will need to use. If you compare a 12 volt and a 24 volt inverter of the same power rating, the 12 volt item will need to draw twice the current. To carry that current, the cables from your battery to the inverter will need to be 4 times the size.A higher voltage system is likely to be more efficient although you will find that most inverters on the market are either 12 or 24 volts. A 48 volt inverter will be more difficult to find and may therefore be more expensive.AC Output PowerAny inverter will have a quoted output power which will be the maximum power level they can provide continuously, measured in watts or killowatts. Inverters will normally however cope with higher levels of power for a short period, enabling them to deal with a short power surge that many appliances will draw at turn on. Practically all electrical appliances will draw extra current for a split second at switch on, including low energy light bulbs.The power output characteristics will vary between different inverters but they may be able to produce 10% over the rated figure for 5 minutes, 50% over for 5 seconds, more for 1 second.Continuous output power capabilities of any inverter may be affected by the battery supplying the DC input voltage. The battery will need to be large enough to be able to supply the high current needed for a large inverter without the battery voltage dropping too low .Continuous output power capabilities may also be affected by the ambient temperature. An inverter that is producing high power will produce heat that is normally dissipated with the help of a fan. If you are experiencing high air temperatures, your inverter may not be able to cope with continuous high outputs without over heating and shutting down.Inverter EfficiencyBy efficiency, we are really saying, what percentage of the power that goes into the inverter comes out as usable AC current (nothing is ever 100% efficient, there will always be some losses in the system). This efficiency figure will vary according to how much power is being used at the time, with the efficiency generally being greater when more power is used.Efficiency may vary from something just over 50% when a trickle of power is being used, to something over 90% when the output is approaching the inverters rated output. An inverter will use some power from your batteries even when you are not drawing any AC power from A 3Kw inverter may typically draw around 20 watts from your batteries when no AC current is being used. It would then follow that if you are using 20 watts of AC power, the inverter will be drawing 40 watts from the batteries and the efficiency will only be 50%.A small 200W inverter may on the other hand only draw 25 watts from the battery to give an AC output of 20 watts, resulting in an efficiency of 80%.Larger inverters will generally have a facility that could be named a "Sleep Mode" to increase overall efficiency. This involves a sensor within the inverter sensing if AC power is required. If not, it will effectively switch the inverter off, continuing to sense if power is required. This can usually be adjusted to ensure that simply switching a small light on is sufficient to "turn the inverter on".This does of course mean that appliances cannot be left in "stand-by" mode, and it may be found that some appliances with timers (eg washing machine) reach a point in their cycle where they do not draw enough power to keep the inverter "switched on", unless something else, eg a light, is on at the same time.Another important factor involves the wave form and inductive loads (ie an appliance where an electrical coil is involved, which will include anything with a motor). Any waveform that is not a true sine wave (ie is a square, or modified square wave) will be less efficient when powering inductive loads - the appliance may use 20% more power than it would if using a pure sine wave.PWM Inverters.Now a days most of the inverters available in the market utilizes the PWM (Pulse Width Modulation) technology. The inverters based on PWM technology are superior in many factors compared to other inverters designed using conventional technologies. The PWM based inverters generally use MOSFETs in the output switching stage. In such cases the inverters are generally termed as PWM MOSFET inverters. The inverters based on PWM technology has a lot of protection and control circuits compared to the traditional inverters.

What is PWM technology PWM or Pulse width Modulation is used to keep the output voltage of the inverter at the rated voltage (110V AC / 220V AC) (depending on the country) irrespective of the output load. In a conventional inverter the output voltage changes according to the changes in the load. To nullify effect caused by the changing loads, the PWM inverter correct the output voltage according to the value of the load connected at the output. This is accomplished by changing the width of the switching frequency generated by the oscillator section. The AC voltage at the output depend on the width of the switching pulse. The process is achieved by feed backing a part of the inverter output to the PWM controller section (PWM controller IC).Based on this feedback voltage the PWM controller will make necessary corrections in the pulse width of the switching pulse generated at oscillator section. This change in the pulse width of the switching pulse will cancel the changes in the output voltage and the inverter output will stay constant irrespective of the load variations.Oscillator circuitOscillator circuit generates the switching frequency. Generally the oscillator circuit will be incorporated in the PWM IC itself.

Driver circuitDriver circuit drives the output section of the inverter according to the switching frequency. Transistors or Specially designed driver ICs are employed in the driver circuit.The driver circuit is some what similar to a preamplifier.Output sectionOutput section drives the load. It consists of a step up transformer for stepping up the battery voltage to the line voltage and an array of switching MOSFET devices for driving the primary of the step up transformer. The output voltage will be available at the secondary of the step up transformerSchematic:First of all draw the schematic in DIP TRACE software

PCB LAYOUT

Inverter PCB Layout Positive:

Inverter PCB Layout Negative

Result60 watt inverter

2.Amps rating. 0.26 Amps

3.Voltage Rating - Usually 230 Volts230 Volts

4.Amps x Volts = Watts60 Watts

5.Watts/1000 = kilowatts or kW.06 kW

6.Hours used in month (use an average) 660Hours

7.Kilowatts x Hours = Kilowatt Hours or kWh39 KWh

8.Cost of electricity (in price per kWh)450 Paise

9.kWh x PAISE = Cost (in paise) to run the Item for 1 month17550 Paise

10.Divide by 100 to get to Cost in Rs to run Item for 1 month175.5 Rs

Total Amount save per month175 Rs

ConclusionsTo complete this project in an effective manner a thorough understanding of solar technology and important aspects of it is essential. A variety of different applications were researched and determined whether or not they are even feasible at the current state of solar technology. The most feasible application for solar power is for remote locations requiring small quantities of power to run lighting, pumps, and other low power applications. Thats why we design a solar inverter of 60w to fulfill the above requirement. The sun has the ability to give off lots of energy however solar panels can only convert a small amount of solar energy to electrical energy due to inefficiency in solar panel technology.