METAL DETECTOR CIRCUIT

This design has not been called a GOLD detector as this name has been left for the more complex detectors that actually discriminate been gold and other metals. There is an enormous difference between detecting gold and ordinary metals (called base metals). How the detector work? The circuit is an oscillator and the way it keeps oscillating is due to positive feedback. This is the case with all oscillators and the component that provides the feedback is the 1n capacitor between the collector and emitter of the transistor. It may seem unusual that the transistor can be turned on via the emitter to keep it oscillating, but in fact it does not matter if the emitter or base receives a signal as the important factor is THE VOLTAGE DIFFERENCE between these two terminals. If the base is kept fixed and the emitter voltage is reduced, the transistor sees a higher voltage between the base and emitter and it is turned ON harder. If the voltage on the emitter increases, the transistor turns OFF as the difference between the two is reduced. This is exactly what happens in this circuit. The 1n capacitor between the collector and emitter influences the voltage on the emitter to turn the transistor on and off. It does this by constantly monitoring the voltage on the tuned circuit and passing the change to the emitter. In this project, the TUNED CIRCUIT is the parallel components consisting of the inductor (the search coil) and the 1n capacitor across it. This is called an LC circuit in which the L is the inductance of the inductor in Henries (or mH or uH) and C is the capacitance of the capacitor in Farads (or uF or nF or pF). We start when the transistor turns ON and allows a pulse of energy to enter the tuned circuit (later you will see how the transistor turns on). The pulse of energy (current) starts by trying to entering both the coil and capacitor. You would think the coil has the smallest resistance but the capacitor is uncharged and presents a theoretical zero resistance and begins to charge. When a small voltage appears across it, you would think the coil would become the least resistance as it consists of only a few turns of copper wire.

METAL DETECTOR CIRCUIT

This design has not been called a GOLD detector as this name has been left for the more complex detectors that actually discriminate been gold and other metals. There is an enormous difference between detecting gold and ordinary metals (called base metals). How the detector work? The circuit is an oscillator and the way it keeps oscillating is due to positive feedback. This is the case with all oscillators and the component that provides the feedback is the 1n capacitor between the collector and emitter of the transistor. It may seem unusual that the transistor can be turned on via the emitter to keep it oscillating, but in fact it does not matter if the emitter or base receives a signal as the important factor is THE VOLTAGE DIFFERENCE between these two terminals. If the base is kept fixed and the emitter voltage is reduced, the transistor sees a higher voltage between the base and emitter and it is turned ON harder. If the voltage on the emitter increases, the transistor turns OFF as the difference between the two is reduced. This is exactly what happens in this circuit. The 1n capacitor between the collector and emitter influences the voltage on the emitter to turn the transistor on and off. It does this by constantly monitoring the voltage on the tuned circuit and passing the change to the emitter. In this project, the TUNED CIRCUIT is the parallel components consisting of the inductor (the search coil) and the 1n capacitor across it. This is called an LC circuit in which the L is the inductance of the inductor in Henries (or mH or uH) and C is the capacitance of the capacitor in Farads (or uF or nF or pF). We start when the transistor turns ON and allows a pulse of energy to enter the tuned circuit (later you will see how the transistor turns on). The pulse of energy (current) starts by trying to entering both the coil and capacitor. You would think the coil has the smallest resistance but the capacitor is uncharged and presents a theoretical zero resistance and begins to charge. When a small voltage appears across it, you would think the coil would become the least resistance as it consists of only a few turns of copper wire.

Inverter 100W 12VDC to 220V by IC 4047 - IRF540

Inverter 100W 12VDC to 220V by IC 4047 - IRF540

This is inverter 100W circuit, use IC 4047 alike inverter 100W transistor I use Mosfet IRF540 instead Transistor 2N3055. It good Idae, power output 100W from transformer 2-3A. Read detail more in circuit.

Circuit DC24V to AC220V Inverter 300W by NE555,CA3130,MJ15003

This is circuit Inverter 300, Input battery 24V to Output 220V 50Hz 300W. Use Component IC 4027,NE555,CA3130,7805 and Transister MJ15003

Circuit Inverter 100W by IC 4047 + 2N3055

Circuit Inverter 100W by IC 4047 + 2N3055 This circuit Inverter input 12V (battery 12V) to out 220V 50HZ, Eesy circuit because less component to use. It use IC 4047 (oscillator 50HZ) and Power Transistor 2N3055 x 2 ,OUTPUT Power 100W.

12VDC Fluorescent Lamp Driver

A number of people have been unable to find the transformer needed for the Black Light project, so I looked around to see if I could find a fluorescent lamp driver that does not require any special components. I finally found one in Electronics Now. Here it is. It uses a normal 120 to 6V stepdown transformer in reverse to step 12V to about 350V to drive a lamp without the need to warm the filaments. Circuit diagram Parts: C1 100uf 25V Electrolytic Capacitor C2,C3 0.01uf 25V Ceramic Disc Capacitor C4 0.01uf 1KV Ceramic Disc Capacitor R1 1K 1/4W Resistor R2 2.7K 1/4W Resistor Q1 IRF510 MOSFET U1 TLC555 Timer IC T1 6V 300mA Transformer LAMP 4W Fluorescent Lamp MISC Board, Wire, Heatsink For Q1 Notes: 1. Q1 must be installed on a heat sink. 2. A 240V to 10V transformer will work better then the one in the parts list. The problem is that they are hard to find. 3. This circuit can give a nasty (but not too dangerous) shock. Be careful around the output leads.

CMOS INVERTER USING 4047

Using this circuit you can convert the 12V dc in to the 220V Ac. In this circuit 4047 is use to generate the square wave of 50hz and amplify the current and then amplify the voltage by using the step transformer. Circuit diagram   How to calculate transformer rating The basic formula is P=VI and between input output of the transformer we have Power input = Power output For example if we want a 220W output at 220V then we need 1A at the output. Then at the input we must have at least 18.3V at 12V because: 12V*18..3 = 220v*1 So you have to wind the step up transformer 12v to 220v but input winding must be capable to bear 20A.

INVERTER CIRCUIT USING 4047 IC(CMOS)

SIMPLE INVERTER CIRCUIT USING ASTABLE MULTIVIBRATOR

Part Total Qty. Description Substitutions C1, C2 2 68 uf, 25 V Tantalum Capacitor R1, R2 2 10 Ohm, 5 Watt Resistor R3, R4 2 180 Ohm, 1 Watt Resistor D1, D2 2 HEP 154 Silicon Diode Q1, Q2 2 2N3055 NPN Transistor (see "Notes") T1 1 24V, Center Tapped Transformer (see "Notes") MISC 1 Wire, Case, Receptical (For Output) Notes Q1 and Q2, as well as T1, determine how much wattage the inverter can supply. With Q1,Q2=2N3055 and T1= 15 A, the inverter can supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power. The easiest and least expensive way to get a large T1 is to re-wind an old microwave transformer. These transformers are rated at about 1KW and are perfect. Go to a local TV repair shop and dig through the dumpster until you get the largest microwave you can find. The bigger the microwave the bigger transformer. Remove the transformer, being careful not to touch the large high voltage capacitor that might still be charged. If you want, you can test the transformer, but they are usually still good. Now, remove the old 2000 V secondary, being careful not to damage the primary. Leave the primary in tact. Now, wind on 12 turns of wire, twist a loop (center tap), and wind on 12 more turns. The guage of the wire will depend on how much current you plan to have the transformer supply. Enamel covered magnet wire works great for this. Now secure the windings with tape. Thats all there is to it. Remember to use high current transistors for Q1 and Q2. The 2N3055's in the parts list can only handle 15 amps each. Remember, when operating at high wattages, this circuit draws huge amounts of current. Don't let your battery go dead :-). Since this project produces 120 VAC, you must include a fuse and build the project in a case. You must use tantalum capacitors for C1 and C2. Regular electrolytics will overheat and explode. And yes, 68uF is the correct value. There are no substitutions. This circuit can be tricky to get going. Differences in transformers, transistors, parts substitutions or anything else not on this page may cause it to not function. If you want to make 220/240 VAC instead of 120 VAC, you need a transformer with a 220/240 primary (used as the secondary in this circuit as the transformer is backwards) instead of the 120V unit specified here. The rest of the circuit stays the same. But it takes twice the current at 12V to produce 240V as it does 120V.

Tl494 AS USE TO SUBTITUTE FOR SG3524N

INVERTER: An inverter is an electronics device that converts battery DC to an AC signal it is the same thing as an oscillator. The AC signal can be of various waveforms; sinusoidal, rectangular, square, saw tooth, etc. The type of waveform that we use in our industrial and domestic homes is a sinusoidal wave; this is the best waveform that can run our appliance with out any problem of over heat.      Most model produce a modified square wave. This waveform allow home owners to run 98% of the typical loads in a house such as fluorescent lights, TVs, stereos, vacuums and power tools. The few limitations include some type of electronic controls like dimmer, switches, sensitive electronics like laser printers and photocopiers, and some small rechargeable devices. Occasionally some of these products will not work, or even fail, with modified square wave power. Some appliances like microwave may be noisier and stereo equipment and TVs may have a slight hum or buzz with this type of inverter power.     Inverters that produces pure sine wave to mimic convectional grid power eliminates background noise so that all appliance, including electronics, work without problem. They are particularly suited for sensitive electronics found in some computers and higher quality sound equipment.                                  INVERTER FOR HOMES…    In large remote residences, particularly those using auxiliary generators, inverters can reduce the cost of power generator by up to 90%. Most inverters include a stand-by battery charger, so that when the generator is on, the batteries are automatically recharged. Once the generator is turned off, the inverter system powers the same AC circuits. Not only do you have quiet power available 24 hours a day, but in most cases the fuel savings alone can pay for the complete cost of the inverter system in less than a year!                                       WHY DO I NEED AN INVERTER?      Inverter converts DC battery power to standard AC power. They allow you to run regular 120V, 220VAC appliances; including TVs, computers, microwaves and power tools. With an inverter your AC loads are run off your batteries and they can be used any time of day and night - without a generator – and definitely during a utility power failure.        When designing an inverter the power rating of the load is taken into consideration at maximum capacity. Choose a size that can power the appliance you plan to use. Typical sizes installed in our home systems are 1000W to 2500W. Larger inverters from 4KW to 11KW are used in large power systems and industrial applications. Inverters are rated according to the continuous power that they can produce; however, they are also designed to deliver large amounts of current for short period of time – a feature called surge capacity.                                  DESIGN OF AN INVERTER     When designing an inverter, the first thing that comes to mind is an oscillator circuit. An oscillator is an electronic device that converts battery DC to an AC signal. The AC signal produce are non sinusoidal – they are AC signals that shows a great deviation from sine/cosine waveform; square wave, rectangular wave, saw tooth wave, trapezoid wave, quasi sine wave, etc (are all complex waves). However, sine wave can be generated by using special kind of oscillators such as Wien Bridge, Hartley oscillator, RC oscillator, and other Radio frequency oscillators. This kind of wave is not very easy to generate.              The use of relaxation oscillators can produce square wave, quasi sine wave etc. Examples of these are the Multivibrators; Astable, Monostable, and the Bistable (flip- flop).     It is note worthy that it is the oscillator that produces the waveform signal for the inverter. So, the choice of oscillator matters.

THYRISTOR INVERTER

THYRISTOR INVERTER   The principle and design of this kind of inverter is based on the class D commutation. The topology is also reliable and works on transformer less operation. This inverter circuit has the following advantages:   Capability of a wide range of frequency variation. Capability of excellent voltage regulation Low commutation losses Low no load losses Transformer less operation and therefore higher speed of response as well as higher full load operating efficiency.       The circuit diagram is shown below      Auxiliary Impulse Commutated Inverter   As shown above, the circuit consists of two main thyristors SCR1 and SCR2 two auxiliary thyristors SCR3 and SCR4, the feedback diodes D1 andD2 and the commutating circuit components L and C. The load R1 is connected between the pole point P and centre tap of DC supply. In order to explain the detailed circuit operation it is assumed that the circuit has attained the steady state while operation. It is also assumed that thyristor SCR1 is conducting and the current is flowing through the load from right to left, through upper half of the DC supply (V/2). The capacitor C is charged to its maximum voltage Vcmax with right hand side plate being positive, as shown. Now any time SCR1 has to be turned -- off, the anode is fired. The circuit consisting of C, L, T1 and T2 oscillates to reverse the charge across C. Thus, the net current through SCR1 is now the algebraic sum of the load current and the oscillatory cycle current. If the oscillatory cycle current is more than the load current, for a period of time higher than the turn  off time toff  of the device, the thyristor SCR1 will turn off the diode D1 in the mean time becomes forward biased. However, in case the charge across the plate of the capacitor is not fully reversed and SCR1 has recovered its blocking capability, the diode D1 will allow the oscillatory current to flow, helping C to reverse the charge. While the thyristor SCR1 is still conducting SCR2 is fired. The load current now transfers to SCR3 via SCR1, C and L, thereby helping the capacitor to develop its full charge in reversing direction (-Vcmax). As and when C is fully charged, the current through SCR1 dies down to zero. Thyristor SCR3 therefore turns off by itself. The load current now flows through SCR4 via the lower half of DC supply (V/2) from left to right. Thus, the direction of current through the load is reversed.   Any time when SCR2 is to be turned off, SCR4 is fired. The capacitor, which has been fully charged with –Vcmax across its plates, reverses through SCR3, SCR2 and L; thus pushing the oscillatory cycle current through SCR2 in the direction opposite to the load current. The commutation process repeats similar to that already described for commutation of SCR1. While SCR2 is still conducting fire SCR4 so as to make up the loss of charge across C (if any) during commutation of SCR2. As the end of this process when C is fully charged to Vcmax, the thyristor SCR2 turns off by itself, leaving SCR1 to continue conduction of current through the load from right to left. Thus, one complete cycle of operation is completed.   This inverter is very popular in all industrial applications and is therefore very widely used for variable speed drives.      MODIFIED SINGLE- PHASE Mc MURRAY INVERTER   The auxiliary impulse commutated inverter (also popularly known as Mc Murray inverter) discussed in the preceding sub-section is one of the circuit techniques that is used to generate the pulse width Modulated (PWM) voltage. The basic circuit can be used as a building block in either single phase as half bridge (to generate a square waveform) or as full bridge (to generate a quasi square waveform). The main objective to use this circuit as a full bridge is to generate a quasi square or stepped load voltage wave, rather than square wave. The later is preferred in an attempt to reduce harmonics in the output waveform.   The full bridge consists of two identical inverters. While inverter 1 consists ofT1 and T2 as its main thyristors; inverter 2 has its main thyristors as T3 and T4. The two half bridges inverter 1 and inverter 2 are independently fired with a phase displacement between the two. The stepped load voltage waveform obtained at the output of bridge inverter is shown below. Since the load is connected between the two poles P1 and P2, the voltage across the load results into a stepped (quasi square) waveform with much lower harmonic content as compared to that of the square wave inverter.

TRUE INVERTER POWER

True inverter power=KVA Rating of Transformer * Power Factor.

For its losses, since it not a true sine wave, tita=90/2=45 degree.
Therefore, Power Factor=COS45=0.7071

True inverter Power=Transformer KVA RATING * COS45.
For 1KVA,
True inverter power=1000*COS45
True inverter Power=700W the require fuse rating will be
I=700/230=3.0A.

DEEP CYCLE BATTERY

Deep Cycle Batteries We stock The Concorde deep cycle AGM, Surrette, and Crown industrial and deep cycle batteries. See what is available on our webstore. Under Construction Our Deep Cycle Battery FAQ is here. Recently updated.

Transformers and Autotransformers

Transformers and Autotransformers Monophase and threephase: from 50 VA to 80 kVA           Technical Characteristics Our monophase and threephase transformers and autotransformers are designed to meet the following priority requirements: Insulation class E for overtemperature max 75°C with ambient temperature of 40°C max. The insulation is subjected to the dielectric strength test: 4 kV between the primary and secondary windings and 2.5 kV between these windings and the ground. The listed power refer to continuous working with power factor = 1 and frequency 50-60 Hz. Fullpower data always refer to the maximum voltage. For transformers having many secondary voltages has to be specified the drawing power on every voltage. The terminal boards eliminate the risk of accidental contact and are made of self-extinguishing material. COMPLIANCE WITH THE STANDARDS CEI 14-4/8           Insulation Transformers Monophase: from 500 VA to 30 kVA - Trimonophase: from 3 kVA to 40 kVA - Threephase: from 3 kVA to 75 kVA         TS-8  10 kVA Technical Characteristics Our monophase and threephase insulation transformers are designed to meet the following priority requirements: Insulation class E for overtemperature max 75°C with ambient temperature of 40°C max. The insulation is subjected to the dielectric strength test: 5 kV between the primary and secondary windings and 2.5 kV between these windings and the ground. Antijamming screening between the primary and secondary windings. The listed power refer to continuous working with power factor = 1 and frequency 50-60 Hz. High efficiency (95%).. No induced harmonic distortion. COMPLIANCE WITH THE STANDARDS EN 61558-2-4

Commercial use of Renewable Energy

Commercial use of Renewable Energy  Renewable energy represents a viable alternative to grid sourced electricity for most sections of Commerce and Industry. In all cases there is an environmental benefit to an appropriately installed system, in the majority of cases, the installation can show real cost and business benefits. Solar Water Heating can be more appropriate for commercial activities where a regular supply of hot water is required during the daylight hours rather than the domestic environment where there is a need to balance storage of hot water for use in the morning and evening with generation during the day.  Electricity generated from solar electric panels is available during the hours of business, a Solar PV installation can be tailored to provide electricity up to the normal level of consumption, thus there is no requirement for export metering nor associated administration. Perhaps the most appropriate installation would be Wind Turbines, in particular where there is a continuous process. Though the majority of energy might still be grid fed, 100% of the electricity from a tailored wind turbine system would supplant mains fed electricity. Thus the relative value of the per Kwh wind generated electricity would be the same as the 'delivered' value of mains electricity. Though the capital cost of renewable energy installations might appear un-economic. For the business user there are grants and significant tax incentives.  BrightLightSolar has many years of experience in energy and utility cost management including understanding the grant application process and tax incentives available. We are able to provide a full service including identifying and sourcing additional funding, recommending and installing the most approriate renewable energy equipment      Telecommunications  As more areas are linked to the expanding GSM network the need for reliable, remote power increases. The power required by GSM transmitters, receivers and Microwave links is reducing as technologies improve. This means that solar energy in this field is becoming more and more competitive and cost effective, especially as a carefully designed solar power system will provide uninterrupted power 365 days a year. Systems of this type operate by charging a large battery bank when the sun shines. This stores energy for cloudy days and for operation at night time. Regional solar data is used to provide monthly average forecasts for power output from the solar and using the worst solar month as a base line a system can be dsigned that will provide clean, reliable power to the equipment all year round. Since each piece of equipment is slightly different in the way it operates and the precise amount of power it consumes, and because every area of the world has quite different sunshine levels, it is necessary to take each application on a case by case basis. If you have a potential Telecoms application then we would be pleased to hear from you and would be happy to work with you to produce a solar power system engineered for your application. Please use the questionnaire provided to give all the relevant details.   Businesses around the world are discovering that solar can provide real advantages as a source of power generation.  If your business is located in an area that lacks a reliable supply of grid electricity, you should consider solar for your needs. Bright Light Solar Ltd has the technical and practical expertise to deliver cost-effective energy solutions to your business. Our systems can be used either by themselves or in conjunction with an alternative (but intermittent) energy source - such as grid electricity or diesel generation. Please contact us for further details.      commercial comment       Businesses & Communities - Case Study    Online Catalogue > Commercial Solar Energy  ©2007 Bright Light Solar Ltd

SG3524N(PWM INVERTER IC)

Sg3524N is a regulated pulse width modulator (PWM) power control circuitry with low stand-by current. PWM is a good sine wave approximation. Nearly all types of equipment will run on this signal. The IC incorporates all the functions required in the construction of a regulated power supply, inverter, or switching regulator on a single chip. They can be used as a control element for high power-output application.
The Sg3524 is designed for switching regulators of either polarity,transformer-coupled d.c to d.c converter, transformerless voltage doublers and polarity converter applications employing fixed frequency, pulse-width-modulation (PWM) techniques. The complementary output allows either single ended or push –pull application. Each device includes an on-chip regulator, error amplifier, programmable oscillator, pulse-steering flip-flop, two uncommitted transistors, a high –gain comparator and current limiting and shut down circuitry. The Sg3524 has operating temperatures between 00C to 700C.
This IC Sg3524 can operate at a maximum voltage of 40V, the collector output current is 100mA and reference output current 50mA with lead temperature of 2600C.

OPERATION OF SG3524N
The SG3524 is a fixed frequency pulse width modulation voltage regulator control circuit. The regulator operates at a fixed frequency that is programmed by one timing resistor RT and one timing capacitor CT. RT establishes a linear control of the output pulse duration(width) by the error amplifier. The SG3524 contains an on board 5V regulator that serves as a reference, as well as supplying the SG3524 internal regulator control circuitry by a resistor ladder network to provide a reference within the common-mode range of the error amplifier or external reference can be used.

A second resistor divider network senses the output and the error signal is amplified. This voltage is then compared to the linear voltage ramp at CT .. The resulting modulated pulse out of the high-gain comparator is then steered to the appropriate output transistor Q1 and Q2 by pulse –steering flip-flop, which is synchronously toggled by the oscillator output.
The frequency of oscillation is mathematically given, thus.
Fo =1.30/RT*CT
Where
RT is in kilo Ohms
CT is in micro Farad
F0 is the frequency in Hz

For the purpose of this project, CT and RT were carefully selected and calculated for a frequency of 50Hz.

THE OUTPUT CIRCUITRY
The Sg3524 contains 2 identical NPN transistors, the collector and emitters of which are uncommitted. Each transistor has anti-saturation circuitry that limits the current through the transistor to a maximum of 100mA for fast response.
There are wide varieties of output configurations possible when considering the application of Sg3524 as a voltage regulator control circuit. They can be segregated into 3 basic categories;
capacitor diode –coupled voltage multipliers
Inductor- capacitor-implemented single ended circuit.
Transformer-coupled.

HAPPY NEW YEAR!

Happy new year to all my fans who have made this web a wonderful one.

INVERTERS AND OSCILLATORS

INVERTER:
An inverter is an electronics device that converts battery DC to an AC signal it is the same thing as an oscillator. The AC signal can be of various waveforms; sinusoidal, rectangular, square, saw tooth, etc. The type of waveform that we use in our industrial and domestic homes is a sinusoidal wave; this is the best waveform that can run our appliance with out any problem of over heat.

Most model produce a modified square wave. This waveform allow home owners to run 98% of the typical loads in a house such as fluorescent lights, TVs, stereos, vacuums and power tools. The few limitations include some type of electronic controls like dimmer, switches, sensitive electronics like laser printers and photocopiers, and some small rechargeable devices. Occasionally some of these products will not work, or even fail, with modified square wave power. Some appliances like microwave may be noisier and stereo equipment and TVs may have a slight hum or buzz with this type of inverter power.

Inverters that produces pure sine wave to mimic convectional grid power eliminates background noise so that all appliance, including electronics, work without problem. They are particularly suited for sensitive electronics found in some computers and higher quality sound equipment.

INVERTER FOR HOMES…
In large remote residences, particularly those using auxiliary generators, inverters can reduce the cost of power generator by up to 90%. Most inverters include a stand-by battery charger, so that when the generator is on, the batteries are automatically recharged. Once the generator is turned off, the inverter system powers the same AC circuits. Not only do you have quiet power available 24 hours a day, but in most cases the fuel savings alone can pay for the complete cost of the inverter system in less than a year!

WHY DO I NEED AN INVERTER?
Inverter converts DC battery power to standard AC power. They allow you to run regular 120V, 220VAC appliances; including TVs, computers, microwaves and power tools. With an inverter your AC loads are run off your batteries and they can be used any time of day and night - without a generator – and definitely during a utility power failure.

When designing an inverter the power rating of the load is taken into consideration at maximum capacity. Choose a size that can power the appliance you plan to use. Typical sizes installed in our home systems are 1000W to 2500W. Larger inverters from 4KW to 11KW are used in large power systems and industrial applications. Inverters are rated according to the continuous power that they can produce; however, they are also designed to deliver large amounts of current for short period of time – a feature called surge capacity

DESIGN OF AN INVERTER
When designing an inverter, the first thing that comes to mind is an oscillator circuit. An oscillator is an electronic device that converts battery DC to an AC signal. The AC signal produce are non sinusoidal – they are AC signals that shows a great deviation from sine/cosine waveform; square wave, rectangular wave, saw tooth wave, trapezoid wave, quasi sine wave, etc (are all complex waves). However, sine wave can be generated by using special kind of oscillators such as Wien Bridge, Hartley oscillator, RC oscillator, and other Radio frequency oscillators. This kind of wave is not very easy to generate.

The use of relaxation oscillators can produce square wave, quasi sine wave etc. Examples of these are the Multivibrators; Astable, Monostable, and the Bistable (flip- flop).

It is note worthy that it is the oscillator that produces the waveform signal for the inverter. So, the choice of oscillator matters.

TRANSFORMER FOR INVERTER

www.micinverters.blogspot.com
www.michaeloladipo.netfirms.com

> TRANSFORMER
> A transformer may be defined as a piece of apparatus
> without a continuously moving part which employs the
> principles of electromagnetic induction to transform
> alternating or intermittent voltage or current in one
> winding into alternating voltage or current in one or more
> windings, usually of different value of voltage or current.
> A transformer used to increase voltage of an a.c is called
> step up transformer while the one used to decrease voltage
> of an a.c is called step down transformer.
> Moreover, transformer can also be used to isolate one
> circuit from another, which ensures safety and guide against
> electric shock when working on the low side of an a.c.
>
> A transformer consists of laminated sheets made of silicon
> steel insulated from one another. This reduces eddy current
> loss. The vertical positions of the core are referred to as
> limb and the top and bottom positions are the yoke. Both the
> primary and secondary coils are wound on the limbs. The
> primary coil is connected to the a.c supply while the
> secondary is usually connected to the load.
>
> 2.15 TYPES OF TRANSFORMERS
> There are different types of transformers:
> 1. Single phase transformers
> 2. Three phase transformers
> 3. Auto-transformers
> 4. Current transformers
> 5. Voltage (or potential) transformers
> 6. Power transformers.
> Power transformers have a high utilization factor, that is,
> they are designed to run with almost constant load, which is
> equal to their rating or capacity.
> The maximum efficiency is designed to be at full load, this
> means that the full load winding losses must be equal to
> core losses.
> 2.16 TRANSFORMER COOLING
> When transformer is supplying power to a load, heat is
> generated in the winding and core due to losses. The heat
> dissipated due to losses should be transferred away from the
> winding and core of the transformer to avoid damage.
> The cooling methods used are:
> 1. Air cooled system: - The transformer casing is
> perforated on both sides. Air circulates through the unit by
> convention. This is usually confined to small transformer of
> the range 1KVA – 5KVA.
> 2. Oil –filled cooling system
> 3. Water cooled system
> 4. Air blast (force air) cooling system.

INTRODUTION TO INVERTER DESIGN

Inverters are electronic circuits converting a D.C. power as a primary power source into A.C. power of predetermined frequency, amplitude and phase.
In principle, the parameters describing the resulting A.C voltage (frequency, amplitude, phase number, e.t.c.) can be arbitrarily chosen. In practice, single phase and three phase realization are most common. Frequency is limited by the dynamic behavior of the electric element chosen.
The pole changes required to turn out an A.C voltage is performed by means of suitably chosen electronic switching elements usually transistors or thyristors. Depending on the switching elements used, we have thus, a thyristor switching inverter and a transistor switching inverter.
Furthermore, due to elimination of mechanical contacts, transistor and /or thyristor inverters are not subject to wear, and there is no soot deposit. They are faster in term of switching speed, they are portable and are maintenance free.
Moreover, in designing inverter, the basic components; the simple diodes, transistors, the power MOSFETS, the thyristors, the transformers, and Battery are effectively utilized.
2.2 THE DIODE
A diode is a rectifying device, which permits current flow in one direction only, being able to withstand a potential difference without current flow in the opposite direction.
The active material from which the semi-conductor power diodes is formed is silicon, a semi-conducting material, that is, a material of which the conductivity is classified as being between insulating and conducting; its resistance decreases with temperature rise. The diode is a P-N junction device from which all other semiconductor components are made.
The N-type semiconductor has electrons (Negative charges) and P-type semiconductor has holes (Positive charges).

2.3 Operation of the P – N Diode
When the P-type is more positive with respect to the N-type by the application of voltage, the electrons in N-type are pulled to the side of P-type and hole is pulled to the side of N-type. In this way, the electric current flows through the semiconductors. And the diode is said to conduct. Conversely, when the N-type is made more positive with respect to the P-type, by the application of potential difference, electrons in N-type are pulled with positive voltage on the side of N-type and holes in the P-type are pulled with the negative voltage on the side of P-type. In this case, the electrons in the semiconductor do not move an so, the diode will not conduct and is said to be reverse biased.

INTRODUCTION TO UPS

INTRODUCTION

The concept of Uninterruptible Power Supply (UPS) comes to mind because of the challenging problems we encounter in the Nigeria power system.
In Nigeria where we experience unpredicted power cut, voltage fluctuation, low voltage, etc, efforts has been made to substitute for existing power with an alternative power which is usually generator. This ensures that businessmen and other business organizations will be able to meet their customer's day to day needs and requirements in order to efficiently maximize profit.
However, the use of private generators has posed more problems to business men because of the inherent disadvantages associated with maintenance cost, repair due to wear of machine parts and cost of fueling the generator. This makes it exorbitantly expensive to run. Moreover, the noise associated with its operation is a nuisance to the neighborhood, a major source of pollution. Another more dangerous pollutant is the fume released to the atmosphere when the generator is in normal working operation. This is hazardous to the environment and society at large.
Consequently, because of the aforementioned disadvantages associated with generators own by individuals, the inverter provides a clean, noiseless, maintenance free power supply to run our domestic and commercial loads when there is utility failure. By incorporating automatic switching mechanism between utility and inverter, the UPS is defined. The UPS ensures that there is constancy of power to the system in use even if there is utility failure and supplies rated voltage and frequency to load even if utility voltage is low.
The inverter converts DC battery power to standard AC power. They allow us to run regular 230Vac appliances, including TVs, computers, microwave and power tools. Inverter can be used any time of the day and night.
Inverters are rated according to the continuous power that they can produce.. Moreover, for the purpose of this project, a 1KVA uninterruptible power supply (UPS) will be designed and constructed.
The UPS consist of the following incorporated systems:
1. Inverter system
2. Automatic battery charger with controller
3. battery monitor( to automatically disconnect load when battery is low)
4. Automatic voltage control(AVC)
5. Indicators/display to signal 1,2,&3
6. Auto transfer between utility power and inverter.

1.1 THE INVERTER SYSTEM
This converts DC battery voltage to alternating voltage AC. The AC voltage is an approximation of sine wave; it is the pulse width modulation type.

1.2 AUTOMATIC BATTERY CHARGER
This charges the battery immediately when utility power is restored. The charger is a two stage charger which provides a constant current until the battery reaches its rated capacity and then switches to a float voltage. The current then reduces as necessary to maintain the battery at the float voltage (trickle current).

1.3 THE BATTERY MONITOR
This is achieved by use of comparator. The comparator compares the output battery voltage with the input and when battery voltage goes below the set point, it automatically disconnects the load from battery so that battery is not completely flat.

1.4 INDICATOR/DISPLAY
It indicates normal working condition of the above features.

1.5 AUTO TRANSFER SWITCH
These are relay operated switches to automatically switch on/off load from utility to inverter or vice versa. When there is utility failure it switches automatically to inverter and when utility power is restored, it automatically switches from inverter to utility power.

1.6 AUTOMATIC VOLTAGE CONTROL (AVC)
This functions like a voltage regulator. It ensures that there is no much voltage variation from the preset desired value of 230V when load of its rated capacity is impressed on it. This makes the UPS unique.
Moreover, the design of the UPS requires a careful selection of semiconductor parts from the electronic data sheet, the power switching semiconductor device so chosen is the MOSFET. The power MOSFET has a positive temperature coefficient for resistance; hence, paralleling of the device is relatively simple. The popular IRF 150N is selected because it is more versatile, rugged and has a maximum drain current rated 40A, Vds 100V maximum. This component will be carefully mounted on an aluminium heat sink for heat dissipation during working condition.