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V e r t i c a l A x i s W i n d M i l l W i t h S P W M I n v e r t e r
1 | P a g e D e p a r t m e n t o f E L E C T R I C A L 2 0 1 1 G E C , S U R A T
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2 | P a g e D e p a r t m e n t o f E L E C T R I C A L 2 0 1 1 G E C , S U R A T
Vertical axis windmills have a feature that is
particularly attractive- they accept wind from any
horizontal direction and do not need the complicated head
mechanisms of conventional horizontal axis windmills. The
resulting mechanical simplification is sufficient to warrant
interest in any new vertical axis concept that arises.
This wind turbine is a rotating machine which
captures the kinetic energy of the wind and converts it into
electrical energy.
In this project we are trying to utilize the maximum
energy of the wind to rotate the wind turbine n by using shaft
work we can generate the electrical energy.
In this project we are using the Neo-Aero Dynamic
type of blades to run the turbine. Its having four blades and
also it can be operated for any directional wind direction.
Here we are using the Proto type of generator of axial flux
machine principle to convert the mechanical energy to the
electrical energy. We are using for four pole proto typegenerator of a four permanent magnet of NdFeB
(Neodymium Iron Baron) material.
And at the last stage of this project we are making a
SPWM inverter for converting the DC current in to the AC
current for operating any electrical apparatus up to 30Watt.
In 2005, wind accounted
for 1% of the totalelectricity production in
the world. The United
States was third in
utilization of wind energy,
with Germany being the
leading producer.
According to the
Department of Energy,
offshore wind farms could
provide enough energy to
power the entire nation.
In 2006, India overtook
Denmark to become the
fourth largest producer of
wind energy in the world.
According to the latest
study released by Global
Wind Energy Council, the
wind could generate a
'considerable share' of
India's power and the
country's total installed
capacity for wind power
could go up five times to
231GW by 2030.
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During the early seventies, South & Rangie (1971,
1972) conducted wind tunnel tests on a novel Vertical axis
configuration at the National Research Council, Canada, which
showed that the device worked efficiently at high tip speed
ratios but had poor starting torque, In effect, the new device
behaved much like a low solidity horizontal axis machine but
was conceptually a great deal simpler.
It appears that the configuration was originally
discovered and patented by Darrieus. A wide variety of VAWT
configurations have been proposed, dating from the Persian
VAWTs used for milling grain over a thousand years ago,
through to the Darrieus turbine, invented in 1926 by Georges
Darrieus, which has been used extensively for power
generation.
We refer to this configuration as the Darrieus rotor and
when used as a turbine as the vertical axis wind Turbine
(VAWT).The Darrieus rotor (figure) consists of a number of
curved blades rotating about the vertical axis through their
ends, Sections of any blade, in planes normal to the slope of
the major (lengthwise) axis, are of aerofoil shape with the
chords aligned in the azimuthally (azimuth - angular distance
from a north or south point of the horizon to the intersection
with the horizon of a vertical circle passing through a given
celestial body) direction.
Figure1. (The rotor
geometry. The blades
rotate about the vertical
axis.)
Egyptians used wind
energy to sail ships on
the Nile River over 5,000
years ago, whilewindmills were
developed in Persia
about 500 to 900 A.D. to
automate grain-grinding
and water-pumping.
Charles Brush was the
first to use a large
windmill to generate
electricity in Cleveland,
Ohio, in 1888.
Wind energy theory was
discovered in 1919 by
German physicist Albert
Betz and published in his
book Wind-Energy
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Fig. 3.1: Block diagram of project
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Understanding of Block diagram of project:
The block diagram of the project is shown in above figure. It contains main five blocks.
i. The first block is of input device. Here is the input of mechanical energy given bythe wind turbine. And the wind turbine is run by the wind.
ii. The second block is of generator with rectifier. Here the mechanical energy isconverted in electrical energy by means of generator. Here we are using six pole
PROTO type AC generators n this AC output is converted in DC output by using
full wave bridge rectifier.
iii. Third part of this project block diagram is of control circuit which controlling theoutput of the generator and gives the charging current to the battery for charging
the battery. Here we are using liquid battery for backup.
iv. Fourth block contains inverter. Here we made SPWM (sinusoidal pulse widthmodulator) inverter to convert the batterys dc power in to the AC pow er up to
40watt.
v. Output port provides the constant 40watt AC supply.
By using these five parts we made our project. There are main 2 part of this project 1 st
is a charging part and 2nd part is discharging part. First of all we have to run this project
mode in charging part when batteries are fully charged then we can use these batteries in
discharging modes by using the SPWM inverter.
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Neo-Aerodynamic introduces a new, history making technology to extract kinetic
energy from a flowing fluid, providing unheard-of amounts of electricity as the final
result; this rate has not been seen before. During the development of this technology we
have gone from one surprising result to the other. At times we could not believe our eyes
when we read the measurements; in the end we had to settle for what the equipment tells
us.
Neo-Aerodynamic indeed sparks a new energy revolution by providing for the first
time in history a concrete means for humans to harness most of their energy needs through
a renewable resource. For example: a 2m diameter by 2m height hydro Neo-Aerodynamic
device could generate a net power of several megawatts. Neo-Aerodynamic provides the
most inexpensive means to generate electricity even when compared to fossil fuel engines.
Neo-Aerodynamic has a high sensitivity to the fluid stream and a superb rate of
energy return allowing it to be economically deployed in almost every corner of the world.
With wind, you feel it you get it. With water, you see it you get it.
Fig 4.1: Neo aero blades design
In our project we are using this kind of blades. In which a plastic sheet of 0.3 cm
and height is of 121cm and width is of 48 cm. It is mounted on the semicircular PVC pipes
of circumference of circle. The length of this circumference is nearly about 51cm.
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plastic blades are holed by clamps from the top and the bottom. Here all the blades are at
apart from each other. The main axis of this wind mill is also of PVC pipe of 2cm
diameter and 0.4cm thickness.
Fig.4.2: Actual Neo Aero Blade of Project
When wind is blowing this structure is rotates on the least friction vertical bearing.
And this both bearing is tightly holed by means of metallic supports.
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The gear ratio of 1:8 is used to increase the RPM of the blades. The total rpm of this
structure are 42 - 45. And by using gear ratio we get the rpm up to 336 360. And this is
used as an input mechanical work of generator.
A. The Background.
Fluid always goes from high to a low-pressured place. In fluid aerodynamic; when
something stands in its flow it then causes the flow facing front having higher pressure.
Using airfoil in the path of the flow; its aerodynamic effect will cause a lift, like it works
with an airplane.
B. The dynamic.
On the wind facing (wind make) side; the flow are then redirect outward from the
center. It then causes the lift on airfoils to push it turning. Once the device is turning it
causes the center to have lower pressure; the outside air then rushes in to fill those
vacuums. This flow is then redirected to cause lift on the airfoil.
When turning; the special arrange of the airfoil allowing the volume of the air
passing through the upper chamber are always more than of the lower chamber. This also
causes the lift to make the device turn.
In short; Neo-Aerodynamic uses the artificial flow of the air to cause the lift on its
airfoils. That's why it's called Neo-Aerodynamic.
C. The Swept Area.
In case of a horizontal axis propeller it's easy to understand that its swept area is on
the surface that is parallel to the cross section of it axis. In this case it is the same as the
wind facing surface.
In case of a Neo-Aero-Dynamic device the swept area is the same area as the cross
section of the airfoils sweep. It is the surface that's parallel to the cross section of its axis.
Therefore as of the wind, the swept area of a Neo-Aero-Dynamic device is on a horizontal
plane. This concept is very important because we will use the swept area to calculate the
output of a Neo-Aero-Dynamic device.
Its also very important that the commonly understood swept area that we use to
calculate the rated output of the horizontal propeller does not apply to this device because:
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There's no wind move through its airfoils. Turbulence and the attack angle of each airfoil changes at every moment. On each airfoil; the pressure posing on the upper chamber and the lower chamber
are different and constantly changing.
As the result; known methods such as "Betz" limit become useless. Everything weuse to calculate the output has to come from actual measurements on either wind
tunnel test models or real life installation.
Advantages & disadvantages of this type of wind blades
Advantages:
Neo-Aerodynamic works on "you feel it you get it", it does not require years ofobservation and gathering data.
Neo-Aerodynamic mainly works on pneumatic force of the wind therefore it's noteffect by turbulence or wind drag.
Neo-Aerodynamic has phenomenally high capture rate; because its capture rate isat least proportional to its diameter.
Neo-Aerodynamic does not require a tower, allowing equipment to be maintainedat or close to the ground.
Neo-Aerodynamic can be scaled independently its width and or its height to fityour application.
Neo-Aerodynamic works on low wind speed while other technologies provide toolittle.
Neo-Aerodynamic increases its effectiveness along with the density of the medium(air and water) while other decrease.
Neo-Aerodynamic are simple to operate; no yawing, no controller to have it facingto the wind.
Neo-Aerodynamic is safe in reaction to the wind rush. Neo-Aerodynamic are low profile; not being scenic pollution. Neo-Aerodynamic is silent. Neo-Aerodynamic does not have shadow nuisances. Neo-Aerodynamic can be adapted to city/subdivision residential area or backyard. Neo-Aerodynamic works in both air and water medium.
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Hydro Neo-Aerodynamic can be either float or bottom dwelling. Both Hydro and aero devices are compact; easy to be transported or making it
portable.
Disadvantages: As of any technology, there may be a limit of how width and or how high it can be
built.
As of any technology, there may be a new, better "invention"? Being backed by actual models; despite the fact that Neo-Dynamic has the same or
better tip-speed, it usually requires a higher ratio gearbox (more expensive) to take
advantage of capturing the energy when the wind speed is slow.
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The biggest problem with using car alternators for wind power is that they aredesigned to rotate at too high a speed to be practical in wind power applications without
significant modifications. Even a small, seemingly fast windmill might do most of its
work at 600 rpm, not nearly fast enough for a car or truck alternator. This means that
gearing up with pulleys or other methods is needed, so lots of power is lost to friction--a
big problem with wind or water power, but not a problem with a internal combustion
engine.
A standard car or truck alternator is electromagnetic-- meaning that some of the
electricity produced by the unit must be used internally and sent to the armature through
brushes and slip rings to make the magnetic field. Alternators that use electricity to
generate the field current are less efficient and more complicated. They are quite easy to
regulate, however, since the magnetic flux inside can be changed by adjusting the field
power.
Also, the brushes and slip rings wear out, requiring more maintenance. Car and
truck alternators can also be rewound to produce power at lower speeds. This is done by
replacing the existing stator windings with more turns of smaller gauge wire. This project
is not for the faint of heart, but check the inexpensive booklet Alternator Secrets by
Thomas Lindsay if you are interested.
5.1Alternator and Generator Comparison for Wind Power5.1.1 Induction Motor Conversion Alternators
* Advantages: cheap, easy to find, fairly easy to convert, good low-rpm performance.
* Disadvantages: power output limited by internal resistance, inefficient at higher speeds,
machining needed.
* Suitability for Wind Power: OK
Armature converted with permanent magnets:
A normal AC induction motor can be converted into a permanent magnet
alternator at very low cost. Our experiments have shown that these conversions produce
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significant power at very low speeds, but become inefficient quickly at higher power
levels.
An induction motor has a center core with no wires in it, just alternating plates of
aluminum and steel (it will look smooth from the outside). If you rout a groove in this
center core to accept permanent magnets, the unit becomes a permanent magnet alternator!
In practice, wind generators made with these do quite well until they reach 10-20
amps of output. At this point, they become inefficient quickly--it takes a large increase in
wind speed to make only slightly more power, and the rest is wasted as heat inside the
unit. The induction motors are wound with wire that's simply too thin for generating large
amounts of power.
In tests, DanB's PM induction motor conversion windmill peaks at around 25 amps
in 30 mph winds, with a 7-foot diameter prop. By comparison, a 7-foot prop on an
efficient PM alternator made from scratch gives peaks of 50-60 amps in similar winds!
Converted motors also have the tendency to "cog" when starting...you can feel the
resistance when you turn the shaft. This affects low-speed startup somewhat.
If the lesser output in high winds is acceptable to you, these units can make for a
pretty easy wind generator project. Look for AC induction motors of the lowest rpm rating
possible. 3-phase motors will perform better than single phase. Since alternators produce
alternating current (AC), the power must be converted to DC with bridge rectifiers.
5.1.2 DC Generators
* Advantages: Simple and pre-assembled, some are good at low rpm.
* Disadvantages: High maintenance, most are not good at low rpm, large sizes very hard
to find, small ones have limited power output.
* Suitability for Wind Power: POOR to OK
Generators make DC current, and batteries need DC for charging. Generators were
used in automobiles until around 1970, when alternators became more practical (due to the
availability of cheap, small diodes). Even old car generators must spin too fast to be
practical for wind power, but there have been many good plans for modifying them.
Generators are fairly complex compared to alternators. They must have brushes,
and complex commutations. Brushes require maintenance, and commentators can wear
out. For most purposes, alternators are more practical today, although generators do have
certain advantages at times.
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Certain low rpm DC motors can be purchased as
surplus and work very well as 12 volt low rpm generators.
These are from old mainframe computer tape drives, and are
sometimes available in local and mail-order electronics stores,
and on EBay. They don't make a whole lot of power...you can
expect only 100-200 watts of output...but these motors are
almost a science project in a box! Slap on a frame and a 3-4 ft
prop, and you have a small working wind generator.
5.1.3 Induction Motors as Alternators
It's possible to make a 3-phase induction motor produceelectricity, either 3-phase or single phase. This requires a
controller and capacitor. The generator must run at a fairly
constant speed. For this reason, this type of generator is more
suitable for constant-speed hydro power installations than for
wind, where speed varies--though it can be done. We have not
experimented with this technique yet, since we don't have a
suitable hydropower source.
5.1.4 Homemade Permanent Magnet Alternators
* Advantages: Low cost per watt of output, very efficient,
huge power output possible, extremely sturdy construction
* Disadvantages: A time-consuming, somewhat complicated
project, machining needed.
* Suitability for Wind Power: GOODHugh Piggott in Scotland was the pioneer in building
permanent magnet alternators from scratch. Experiments have
consistently shown that homemade PM alternators are the most
powerful and cost-effective solution for building a wind
generator. Their low-rpm performance is excellent, and at high
speeds they can really crank out the amps thanks to their
efficiency.
PM alternators have been based on disc brake
Features of NdFeB:
NdFeB magnets are
sensitive to changes in
temperature.
Additionally, Neodymium
Iron Boron magnets are
prone to rapid oxidation;
salt spray, salt water, and
hydrogen are very harsh
on the magnet.
Coating or plating is
generally recommended
unless using advanced
alloys. Advanced grades
are developed specifically
for applications which
have oxidation rates that
are far below the average
Neodymium Iron Boron
alloys, making them ideal
for applications that
require post assemblyprocessing, due to tight
tolerances in the final
assembly state.
The selection of
Neodymium Iron Boron
magnets in your
applications will depend
on your working
environment. If you usethe magnets at elevated
temperatures, select the
alloys that have a high
intrinsic coercivity (Hci). If
you use the alloy at lower
temperatures (such as
room temperature), you
may select higher Br
materials.
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assemblies, which are very sturdy and have thrust bearings
built into the unit. Larger units are "Disc" or "Axial"
designs...a flat plate of magnets rotating next to a flat plate of
coils. Smaller PM alternators are "Radial" designs, where the
magnets are fastened to the outside radius of the armature.
Since all alternators produce AC, the output must be converted
to DC with bridge rectifiers for battery charging.
These designs are usually single phase for ease of
construction. Three-phase alternators have some advantages
(they are somewhat more efficient, and make better use of
available space), but they are somewhat more difficult to
build.
Here we have made a Permanent Magnet Alternator of 6 poles.
Rotor of alternator:In this project the rotor is made up of a 40 cm diameter
and 0.5 cm thick wooden circular plate on which the 6
permanent magnets are holed by screw arrangement
apartfrom each other.
Fig. 4 shows the practical design of the rotor. In this
alternator we are using a belt conveyor system to convert
higher torque lower RPM of wind blades in lower torque high
RPM of ratio 1:8. Rotor contains a ball bearing. In a ball
bearing, the load is transmitted from the outer race to the ball
and from the ball to the inner race. Since the ball is a sphere,it only contacts the inner and outer race at a very small point,
which helps it spin very smoothly.
In this project the permanent magnets are used of a
3500 gauss NdFeB (Neodymium Iron Baron) material. Sizes
of the magnets are 5*5 cm and 2cm thick. And the thickness of
the axis which is passing through it is of 1.5cm diameter.
NdFeB magnets are mechanically strong and give the best
NdFeB Magnet:
Neodymium Iron Boron
magnetsabbreviated as
NdFeB are a type of rareearth alloy that typically
has two atoms of
Neodymium (Nd), 14
atoms of Iron (Fe), and
one atom of Boron
(B)as its primary elements,
(Nd2Fe14B).There are other
elements that are used to
increase the coercivity, to
gain lower oxidation
characteristics, and to
obtain other desirable
characteristics, which are
generally found in small
quantities (
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fields possible in permanent magnets. The temperature coefficient of Br is higher than
Samarium Cobalt, so the material is more sensitive to temperature changes, ranging from
0.10%/C - 0.13%/C. Neodymium Iron Boron magnets are less expensive, since the main
elements Nd and Fe are abundant, and are mechanically stronger.
Fig.5.1:permanent Magnet Rotor of Alternator
Stator:Here we made a stator which having a total 24 coils 12 coils are of square shaped
of 5 * 5 cm, 21 SWG (standard wire gauge) copper wires having a 45 turns. The coil
winder we used probably wound the coils a little taller than needed, so the unit could be
improved by making the coils a little smaller.
All coils are 30 apart from each other. Bellow figure shows that coils on stator.
Now the upper end of this coils are connected with the another coils which having a
copper wire of 36 SWG, 2300 turns wounded on the round shaped wonder.
After each coil is wound, it is carefully set aside to be glued and clamped over the top of
the stator at a later time. And the thickness of this coil is 2cm. Here it was to line them up
around the stator and put them in exactly the right place.
Totally 12 coils are used, so each of them must occupy a 30 degree arc around the stator.
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Fig.5.2: Stator Coils of 45 turns
Fig.5.3: Stator coil of 2300 turns
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Since there are 4 coil groups, each one must occupy a 90 degree arc around the
stator. This is actually easily estimated by first perfectly aligning the magnets around the
armature (the brake disk), placing all the coils down around the stator (pictured above),
and then placing the brake disc down over the stator, making sure that there is 1 coil
located exactly under each magnet. Sometimes it was necessary to squeeze the coils by
hand so that they would fit in the space provided. Once everything is lined up properly, we
fix it with glue.
Then we took the rotor, centered over the stator, and clamped the whole thing
together tightly. It is very important! When clamped, the thickness of all the coils around
the stator should be the same. Otherwise, when completed the gap between magnets and
coil will be wider in one part of the alternator than another.
Fig.5.4: Stator with both Coils connected in series
So, when one side had thicker coils than another, we would simply adjust the
clamps until it willbe even all around. The thickness of the coil is 2 cm and the air gap
created between coils and magnet is 0.6 cm.
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The generator also has excellent part load efficiency. This is primarily due to the
use of permanent magnet excitation whilst the simple stator core minimizes iron loss.
The stator is of 2 phase. Each phase having 6 coils.And the each coil having 2345turns.
Coil WinderIf we're going to build a generator or a motor, then we're going to need some coils.
Even with permanent magnet rotors as used here, we 'll still need armature windings. Its
pretty hard to get out much power otherwise. Some kind of winder will make the task of
producing consistent coils much easier. The photos below show a simple coil winder of 45
turns coils.
Fig.5.5: Coil winder of 45 turns coil
This is made up of one piece of wood skewed at a square shaped 4.5 cm * 4.5 cm.
For winding 2300 turns coils we use a round shaped winder of Teflon tape which is
shown below.
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Fig.5.6: Coil winder of 2300 turns coil
After winding all the coils we applied an insulation varnish to hold winding. All
coils were wound in the same direction and so that the last turn come out on the same side
of the coil as the first turn. For each coil, the wire extending from the first turn was
arbitrarily chosen to be the "positive" coil lead, and a small loop was twisted in its end in
order to identify it after removing the coil from the winder.
Prior to removing a coil from the coil winder a few inches of fiber reinforced
strapping tape was wrapped around the circumference of its windings to hold them in
place. The reinforced tape was chosen because it holds well, even when moist, and also
because it tears uniformly lengthwise so that a width of tape that covered the spread of the
coils but did not adhere to the coil forms could easily be obtained without having to
actually try to cut the tape lengthwise. Once the windings were taped in place the wire
extending from the spool was cut, (becoming the "negative" coil lead), and the coil was
removed from the winding form, with no danger of the coil unwinding itself.
A hole was drilled in the center of the backing wooden groove circle for the axle to
pass through. The backing wooden groove was turned in high enough up the stator frame
piece to allow clearance for the rotor to spin freely on its axle when the entire generator
unit is assembled on its base.
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Coil Lead ConnectionThe machine is of 2 phase. In a three phase system, the phases are electrically120
degrees apart. But, the stator coils are not (necessarily) physically spaced at 120 degree
intervals on the stator frame. The total number of coils on the stator and the number ofcoils used for each phase affects the physical placement of coils around the stator frame.
Here we are using a 2 phase system as there are a 6 poles and stator having 12 coils
30 apart from each other.
For the generator being described here, there are twelve stator coils, which allow 6
coils to be connected for each of the 2 phases. And, 12 coils means they will be spaced at
thirty degree intervals around the 360 degree perimeter of the stator frame.
The phases are referred to as A, B, and, starting from the right one of the topmostpair of coils on the stator frame, the coils are identified in the clockwise direction as
follows: A1, B1, A2, B2, A3, B3, A4, B4, A5, B5, A6, B6.Where B6 is the left one of the
topmost pair of coils. Each indexed letter of the alphabet refers to one of the coils in the
group of coils that comprises on phase coil set, e.g., coils A1, A2, A3, A4, A5 and A6 are
the coils wired together for phase A.
In phase A A1 is in series with A4.Such that A2 and A3 are in series with A5 and
A6. Then they are connected parallel to get a somewhat higher current.
Fig.5.7 Coil Connections in phase 1 in stator
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But in phase B coils B1, B2, B3, are connected in series with B4, B5, and B6 just
like phase A, but at last they all are connected in series as per the polarity considered at
some instant.
Fig.5.8 Coil Connections in phase 2 in stator
To work properly, at any instant in time each coil in a phase must be contributing
current to the phase of the same polarity and magnitude. Whether a coil is being energized
by the North Pole or the south pole of a magnet determines the polarity of the current
produced in the coil. The distance in its rotating path a magnet is from a coil determines
how much it contributes to the magnitude of the current generated in the coil. (A changing
magnetic field is required to generate current in a wire coil, and motion of the magnets
results in a changing magnetic field.)
Because there are alternating north and south magnet poles, the separate phase
coils cannot be simply connected in series, as the resulting currents generated in the
individual coils in a phase will not match.
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Fig.12: Waveform of the Output of this Generator
Fig.5.9: Side View of Generator
Fig.5.10: Rectifier used to convert AC to DC
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Fig.5.11: Output of the Generator before Rectified
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6.1 What is Inverter (power inverter)?
Many people are confused on two products: inverters (power inverters) and
frequency inverters. Although both have the word of inverter, they are different.
Then what exactly is an inverter (power inverter)? An inverter (power inverter) is
an electrical device that converts DC power or direct current (DC) to AC power or
alternating current (AC). The converted alternating current (AC) can be at any required
voltage and frequency with the use of appropriate transformers, switching, and control
circuits. An inverter (power inverter) allows you to run electrical equipment off your car
or marine battery for mobile applications, emergencies or simple convenience.
Power inverters (inverters) are small rectangular electrical devices that have a
trailing wire with a jack that plugs directly into the cigarette lighter on the dashboard.
Power inverters (inverters) might also come with jumper-like cables for connecting
directly to a battery.
6.2Type of inverter1. Pure Sine Inverter
A pure sine wave inverter, also known as a true sine wave inverter, uses sine
waves, which oscillate regularly in order to produce electrical energy to power appliances.
The sine wave inverter produces sine waves with AC machinery that rotates and creates
the type of electrical wave that is usually produced by the utility company with the use ofa generator. There are many benefits to using a pure sine inverter since all electronic
equipment is designed to be used with sine waves. Additionally, some appliances such as
light dimmers cannot work without the use of sine wave power and microwaves cannot
operate at full output without sine wave power. Pure sine wave inverters are more
expensive than other types of inverters.
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2. Modified Sine InverterA modified sine inverter differs from a pure sine inverter because it operates by
creating step waves instead of regular oscillating waves. As a result of this, most
appliances cannot work with this type of inverter because they require a regular energy
output that cannot be produced using step waves. However, some appliances can operate
with modified sine inverters though they require more power to run since the level of
energy output from the inverter is irregular.
3. Square Wave InverterSquare wave inverters make electrical energy conversions using a series of waves
that have a rectangular form. The signal from the inverter is very noisy and most
appliances cannot function with electrical currents produced by a square wave inverter.
The square wave inverter is one of the earliest types of inverters and, as such, the device is
incompatible with most modern types of electrical equipment. Moreover, the power
produced by this type of inverter can damage some electronic equipment that is sensitive
to the square waves of electrical power.
6.3 Principal of Inverter
An inverter is an electrical device that converts direct current (DC) to alternating
current (AC); the converted AC can be at any required voltage and frequency with the use
of appropriate transformers, switching, and control circuits.
6.4 The working principle of InverterFrom basic principles in terms of application, Inverter is a device that contains
stored energy in order to inverter as the main component, regulated stable frequency
output power protection equipment. Mainly by the rectifier, batteries, power inverters
and static switch of several components.
1) Rectifier
Rectifier is a rectifier device, simply means that the exchange of (AC) into direct
current (DC) devices. It has two main functions: First, the alternating current (AC) into
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direct current (DC), through the supply of filtered load, or the supply inverter; second, to
provide battery charging voltage. Therefore, it is also play a role in charger.
2) BatteryInverter battery is used as a storage energy device, which consists of several cells in series,
with a capacity to maintain its size determines the discharge (supply) time. Its main
function is: When the wind mill is rotating and electricity is generate through Generator,
the energy converted into chemical energy stored in the battery internal; when the
electricity fails, the chemical energy into electrical energy provided to the inverter or the
load.
3) Inverter
Popular speaking, the inverter is a DC (DC) into alternating current (AC) device. It
consists of inverter bridge control logic and filter circuit.
4) Sensing Relay
When there is electricity is available relay is sense the voltage and already in
operated condition. Voltage is applied to relay by step down transformer 230 12 volt.
But suddenly if electricity is not available relay come in its normal position and the
contact of inverter makes. So Relay provides automatic operation of inverter.
Most inverters do their job by performing two main functions: first they convert
the incoming DC into AC, and then they step up the resulting AC to mains voltage level
using a transformer. And the goal of the designer is to have the inverter perform these
functions as efficiently as possible. So that as much as possible of the energy drawn from
the battery or solar panel is converted into mains voltage AC, and as little as possible is
wasted as heat.
Modern inverters use a basic circuit scheme like that shown in Fig.1. As you can
see the DC from the battery is converted into AC very simply, by using a pair of power
MOSFET (Q1 and Q2) acting as very efficient electronic switches. The positive 13.8V DC
from the battery is connected to the centre-tap of the transformer primary, while each
MOSFET is connected between one end of the primary and earth (battery negative). So by
switching onQ1, the battery current can be made to flow through the top.Half of the
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primary and to earth via Q1.Conversely by switching on Q2 instead, the current is made to
flow the opposite way through the lower Half of the primary and to earth.
Therefore by switching the two MOSFET on alternately, the current is made to
flow first in one half of the primary and then in the other, producing an alternating
magnetic flux in the transformers core. As a result a corresponding AC voltage is induced
in the transformers secondary Winding, and as the secondary has about 24 times the
number of turns in the primary, the induced AC voltage is much higher, around 650V peak
to peak. By the way if youre wondering why MOSFET are used as the electronic
switches, to convert the DC into AC, its because they make the most efficient high-
current switches.
When they are off they are virtually an open circuit, yet when they are on they are
very close to a short circuit (only a few milliohms). So very little power is wasted as heat.
6.5 Pulse Width Modulation
There are many forms of modulation used for communicating information. When a
high frequency signal has amplitude varied in response to a lower frequency signal we
have AM (amplitude modulation). When the signal frequency is varied in response to the
modulating signal we have FM (frequency modulation). These signals are used for radio
modulation because the high frequency carrier signal is needs for efficient radiation of the
signal. When communication by pulses was introduced, the amplitude, frequency and
pulse width become possible modulation options. In many power electronic converters
where the output voltage can be one of two values the only option is modulation of
average conduction time.
Here we are using SPWM technical to switching the mosfet.
6.6 Sinusoidal Pulse Width Modulation
Instead of, maintaining the width of all pulses of same as in case of multiple pulse
width modulation, the width of each pulse is varied in proportion to the amplitude of a
sine wave evaluated at the center of the same pulse. The distortion factor and lower order
harmonics are reduced significantly. The gating signals are generated by comparing a
sinusoidal reference signal with a triangular carrier wave of frequency F c. The frequency
of reference signal Frdetermines the inverter output frequency and its peak amplitude AR,
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controls the modulation index M and RMS output voltage VO. The number of pulses per
half cycle depends on carrier frequency.
Sinusoidal pulse width modulation (SPWM) is widely used in power electronics to
digitize the power so that a sequence of voltage pulses can be generated by the on and off
of the power switches. The Sinusoidal pulse width modulation inverter has been the main
choice in power electronic for decades, because of its circuit simplicity and rugged control
scheme. SPWM switching technique is commonly used in industrial applications or solar
electric vehicle applications. SPWM techniques are characterized by constant amplitude
pulses with different duty cycle for each period. The width of this pulses are modulated to
obtain inverter output voltage control and to reduce its harmonic content. Sinusoidal pulse
width modulation is the mostly used method in motor control and inverter application.The
proposed alternative approach is to replace the conventional method with the use of
microcontroller. A use ofP89V51RD2 microcontroller brings the flexibility to change the
real-time control without further changes in hardware. It is also low cost and has a small
size of control circuit for the single phase full bridge inverter. The microcontroller has the
built in dead time control circuit.
6.7 Block Diagram of SPWM inverter
Fig.6.1: Block Diagram of SPWM Inverter
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As per the block diagram we can say that its very simple concept to make an
inverter. There are 7 main parts.
a) control circuit:It is the main part of the inverter where SPWM signals are generated by using
P89V51RD2. 4 Output port of the controller is given to the Mosfet connected in
H-Bridge, which gives proper switching to the Mosfet.
b) Mosfet Driver Circuit:It is made up of a 4 Mosfet IRF3205 connected in H-bridge to give the Output. The
Output of the Control Circuit is primarily fed to an IC TLP250 and then it gives
signal to H-bridge.
c) Step up transformer:Here we are using a transformer of 10v at its primary side and 250v at secondary.
Also secondary transformer has a tapping of 220v and 250v.
d) LC filter:This inverter contains the LC filter for filtration. It is having proper values of
inductor and capacitor to give effective and proper output wave form.
e) Output Port:It provides the output of 230v constant even if main supply fails.
f) Sensing Circuit:Here one Relay is used for sensing that mains supply is on or off. If mains supply
is fails this relay will trip and inverter automatically starts to give the Constant
Output. A switching time of inverter is very less up to 0.5-1 sec.
g) Battery:For backup we have used 2 batteries. Both having same ratings.2 batteries are of12 v, 3.5 AH.
Electrical safety in case of battery: There is no danger of electric shock from a 12
volt battery. But if the wind generators disconnected from the battery, and running fast,
then the voltage will be higher than 12 volts, maybe as high as 50 volts. Do not run the
Generator at high speed without a battery connected.
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6.8 Actual Hardware schematic
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Explanation of the schematic diagram:
Here in our project we have use a P89V51RD2 controller. It is using 5v supply
from the main battery through voltage regulator IC 7805. We used only 4 output pin and
Vcc of the controller for switching the mosfet to generate the Output signal. SPWM can
be generated through the programming of controller. And look up table for SPWM
technique can be made up from the PC software PSIM. From this software we can get the
intersection points of the carrier waves and Sine wave which can be shown below. From
that software we can get SPWM look up table also it is shown below.
6.9 System Design
6.9.1 Overview 8051 Microcontroller
Descripssion:
The P89V51RD2 is a low-power, high-performance CMOS 8-bit microcomputer
with 4K bytes of Flash programmable and erasable read only memory (PEROM). The
device is manufactured using Philipss high-density non-volatile memory technology andis compatible with the industry standard MCS-51 instruction set and pin out. The on-chip
Flash allows the program memory to be reprogrammed in-system or by a conventional
non-volatile memory programmer. By combining a versatile 8-bit CPU with Flash on a
monolithic chip, the PhilipsP89V51RD2 is a powerful microcomputer which provides a
highly-flexible and cost-effective solution to many embedded control applications.
VCC
Supply voltage. +5.0V
GND
Ground.
Port 0
Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can
sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high
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impedance Inputs. Port 0 may also be configured to be the multiplexed low order
address/data bus during accesses to external program and data memory. In this mode P0
has internal pull-ups. Port 0 also receives the code bytes during Flash programming, and
outputs the code bytes during program verification. External pull-ups are required during
program verification.
Port 1
Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output
buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled
high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are
externally being pulled low will source current (IIL) because of the internal pull-ups. Port
1 also receives the low-order address bytes during Flash programming and verification.
RST
Reset input. A high on this pin for two machine cycles while the oscillator is
running resets the device.
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ALE/PROG
Address Latch Enable output pulse for latching the low byte of the address during
accesses to external memory. This pin is also the program pulse input (PROG) during
Flash programming. In normal operation ALE is emitted at a constant rate of 1/6 the
oscillator frequency, and may be used for external timing or clocking purposes. Note,
however, that one ALE pulse is skipped during each access to external Data Memory. If
desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit
set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is
weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in
external execution mode.
PSEN
Program Store Enable is the read strobe to external program memory. When the
AT89C51 is executing code from external program memory, PSEN is activated twice each
machine cycle, except that two PSEN activations are skipped during each access to
external data memory.
EA/VPP
External Access Enable. EA must be strapped to GND in order to enable the device
to fetch code from external program memory locations starting at 0000H up to FFFFH.
Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA
should be strapped to VCC for internal program executions. This pin also receives the 12-
volt programming enable voltage (VPP) during Flash programming, for parts that require
12-volt VPP.
XTAL1
Input to the inverting oscillator amplifier and input to the internal clock operating
circuit.
XTAL2
Output from the inverting oscillator amplifier.
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6.9.2Basic Power Circuit of P89V51RD
6.9.3Power Supply
Simple 12Vdc power supply:
Brief description of operation: Gives out well-regulated +12V or 5v dc output from 12v acinput.
Circuit protection: Built-in overheating protection shuts down output when regulator ICgets too hot
Circuit complexity: Very simple and easy to build Circuit performance: Very stable +12V or 5v dc output voltage, reliable operation Availability of components: Easy to get, uses only very common basic components Design testing: Based on datasheet example circuit, I have used this circuit successfully as
part of many electronics projects
Works on 12v dc input. Here three power supply of this type are used, as shown in circuit above.
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The grounds of this power supply are different.6.9.4 Circuit description
This circuit can give +12V or 5vdc dc output when 12V ac I/P given. The circuit
has over overload and terminal protect
6.9.5Mosfet driver
There are 2 mosfet named IRF3205 are connected in half-bridge. Which are given to
the 2 IC TLP250 and output of the controller is also fed to this IC. Outputs of ICs aregiven to the mosfet which are connected in Half-Bridge. Also battery supply is fed to all
the mosfet. Finally output is given to transformer and that can be filtered by LC filter.
Output waveform is shown in fig.
The power circuit topology and output voltage of half bridge inverter is shown in
Figure. The inverter circuit consists of two controlled static switching elements. The
switching elements can be BJT, MOSFET, and IGBT. The switching elements are labeled
Q1 and Q2 and each of switches has an anti-parallel diode.
It is evident from the presence of the diodes that the switching devices Q1 and Q2
need not have the capability to block the reverse voltages. If the switching element is
power MOSFET, there may not be a need to use the anti-parallel diodes because the
devices structure has an anti-parallel diode. The basis operation of half bridge inverter can
be divided into two operations. If switch Q1 turned on for period ofT/2, the instantaneous
output voltage across the load equal to Vdc/2. If switch Q2 turned on for period ofT/2 to T,
the instantaneous output voltage
Vdc/2 will appear.
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The switching strategy for switch Q1 and switch Q2 must be designed to make
sure both switches not turn on at the same time. If that happens, it is equivalent to a short
circuit across the DC input, resulting in excessive current and possible damage to the
switching element.
Fig.6.2: Single Phase Half Bridge Inverter configuring and waveform
Fig.6.3: Output from the Half bridge
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Fig.6.4 Compare Mainoutput or H bridge Output
6.9.6 Lc Filter
The power circuit section is composed of four parts namely half bridge inverter
circuit, DC power supply, LCfilter and load. SPWM inverters include semiconductor
devices with nonlinear characteristics and can generate dominant harmonics in the system.
The waveform quality of the sensitive load is improved by putting an LC filter at the
output of the SPWM inverter. In order to design an LC filter, there are many methods
available. Optimum performance can be obtained by using in simulation and experimental
studies. A rule of thumb in control theory is that the frequencies of such a configuration
have to have at least a factor of 10 between them to decouple the effects. According to this
rule, for 50-Hz fundamental frequency, resonance frequency has to be at least 500-Hz,
pulse frequency of the inverter output has to be at least5000-Hz. Resonance frequency isdetermined by the product of L and C.
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W =
6.9.7 Software
Fig.6.5: PSIM software outlook for SPWM look up table
Fig.6.6: Intersection between reference sinewave and carrier waves
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From the software PSIM we take the example of the SPWM circuit and take
the output waveform of the 4 mosfet h-bridge. Here we took the two frequency one
is carrier waves of a 1500hz and another is reference sine waves of 50 hz. By
compairing them we get the intersection points and make look up table according to
this intersection points. We use this lookup table to start and stop timer 0 in the
software to generatate SPWM waveforms and it is given to the mosfet h-bridge
circuit.
Table 1
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6.9.8 Flow cart
START
Initialize Timer 0
Start Timer 0
If (i=29)
Yes
No
i=0
j=~j
If Timer 0 Overflow
Interrupt Occures?
i++
If (J=0x00)
TL0=LSB[i]
TH0=MSB[i]
Timer 0 ON
L1 OFF
L2=onoff[i]
(Make L2 ON/OFF according to
SPWM lookup Table)
If (J=0xFF)
TL0=LSB[i]
TH0=MSB[i]
Timer 0 ON
L2 OFF
L1=onoff[i]
(Make L1 ON/OFF according to
SPWM lookup Table)
No
Yes
Yes
No
No
Yes
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6.9.9 Inverter hardware photo
Control circuit :
Fig.6.7: PCB Lay out of Control Circuit and Sensing Circuit
Driver circuit :
Fig.6.8: PCB Layout of mosfet Driver circuit
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Filter circuit:
Fig.6.9: PCB Layout of LC filter
Transformer .(10vac to 220vac):
Fig.6.10: Transformer for step up voltage
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Fig.6.11: Our Inverter
6.9.10 About Battery (Volts, Amps and Watts)
Watts are the units of power. A hairdryer full-on might be 500 watts; on the low-
power setting it might be 200 watts. Higher the power the bigger the charger. Voltage
must be matched to the equipment in use and will be either 12 volts or 24 volts in a boat.
Current indicates the flow of energy from the battery and is measured in amperes (or
amps). Zero current and the battery are not discharging. The higher the current the fasterthe battery will discharge.
A battery is rated in AmpereHour (abbreviated Ah) and this is called the battery
Capacity. For example, a small boat might have a 12 volt 100Ah battery. This battery will
Provide 100 AMPERE-HOURS before needing to be re-charged. This may be taken from
the
Battery as
1 AMP for 100 hours
2 AMPS for 50 hours
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10 AMPS for 10 hours etc.
WATTS are VOLTAGE multiplied by CURRENT, so taking the above example
with the 12 volt Battery
1 AMP x 12 VOLTS = 12 WATTS for 100 hours
2 AMPS x 12 VOLTS = 24 WATTS for 50 hours
10 AMPS x 12 VOLTS = 120 WATTS for 10 hours.
6.9.11 Battery size calculation
The backup time is simply the number of hours, Inverter will be able to run
Lighting load, during Power Failure.
The backup time in hours can be calculated using following Formula:
Backup Time =AH x 12V x N x P.F. x Efficiency of Battery (0.9)
Load in (VA)
Where,
AH stands for Ampere Hour Capacity of Battery
N stands for Number of 12 V Batteries needed
P.F. stands for Power Factor of Inverter
EFF stands for Efficiency of Battery
Load stands for Number of Tubes and Fans
6.9.12 Battery Recharging
Re-charging a battery follows the same principle. The requirement is usually to re-
charge the battery over-night - say in 10 hours. Because a battery is not totally efficient at
converting electrical energy into chemical energy and vice-versa, re-charging a 100Ah
battery requires about 120Ah to be put back into it, and this can be achieved by either
120 Amp-hours / 10 hours = 12 Amps for 10 hours
120 Amp-hours / 15 hours = 8 Amps for 15 hours
120 Amp-hours / 24 hours =5 Amps for 24 hours etc.
Current = watts / volts therefore if, say, the lights add up to 36 WATTS and the battery
Voltage is 12 Volts then The Current taken from the battery will be
36 Watts / 12 Volts = 3 Amps
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If these lights are on whilst the battery is being charged, then the battery charger
must also provide an extra 3 AMPS to power them.
6.9.13 Use of inverter
Inverter should be noted that the use of items:
Do not bring inductive load, such as the Counter, fluorescent lights, air-conditioning so as to avoid damage.
Inverters output load control is about 60% of the best, most reliable. Inverter with load is too light (for example, 1000VA, UPS with 100VA load) may
cause the battery depth of discharge, will reduce the battery life, should be
avoided.
Appropriate discharge, contribute to the activation of cells, such as the long-termnon-stop electricity, every three months to be artificially cut off electricity to use
UPS with a load-discharge time, so you can extend battery life.
For most small Inverter, to work to open Inverter, with load at boot time to avoidstartup, work should be shut down Inverter; for network computer room UPS,
because most of the network is 24 hours, so Inverter must also be running around
the clock.
Inverter charge promptly after discharge to prevent battery damage due toexcessive self-discharge.
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There is low environmental impact. There is no air pollution after manufacture. A massive tower structure is less frequently used, as
VAWTs are more frequently mounted with the lower bearing
mounted near the ground.
Designs without yaw mechanisms are possible with fixedpitch rotor designs.
The generator of a VAWT can be located nearer theground, making it easier to maintain the moving parts.
VAWTs have lower wind startup speeds than HAWTs.Typically, they start creating electricity at 6 m.p.h. (10 km/h).
VAWTs may be built at locations where taller structuresare prohibited.
These are well proven and occupy a relatively smallamount of land in proportion to their electrical output.
VAWTs situated close to the ground can take advantageof locations where mesas, hilltops, ridgelines, and passes funnel
the wind and increase wind velocity.
Modern wind energy converter systems can be set up forindividual houses, or as part of an electricity grid system
interconnected with other types of generating plant.
Because of their smaller footprint, vertical axis turbinesare the perfect solution for the urban setting.
Types of wind turbines
1. Horizontal axis(HAWT)
2. Vertical axis(VAWT)
Problem with HAWT:
The tall towers and
blades up to 45 meters
long are difficult to
transport.
Transportation can
now amount to 20% of
equipment costs.
Reflections from tall
HAWTs may affect side
lobes of radar
installations creating
signal clutter, although
filtering can suppress it.
HAWTs require an
additional yaw control
mechanism to turn the
blades and nacelle
toward the wind.
In order to minimize
fatigue loads due towake turbulence, wind
turbines are usually
sited a distance of 5
rotor diameters away
from each other, but
the spacing depends on
the manufacturer and
the turbine model.
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This means that even if you live in an apartment in themiddle of a bustling city, you can quite easily and practically fit
a vertical axis wind turbine to your building without causing too
much disruption
They also have a number of features attached to them thatmake them much more attractive if one thinks of the usual
objections towards horizontal axis turbines.
In this second post of a very short series, we will look atthese features, and the advantages that make vertical axis
turbines a real alternative to the conventional kind.
When it comes to planning applications, it may be a loteasier to get planning permission for a vertical axis wind turbine,
simply due to the fact that it does not take up as much space, and
in the built environment that is always an advantage.
They emit less noise. There is now ay around this, andthis will annoy those who own horizontal axis turbines. The
vertical turbines do officially make less noise than their
horizontal counterparts. This is obviously a bug winner for some
people, and answers one of the bigger arguments against wind
power outlined in the previous post.
When it comes to wildlife, a vertical axis turbineprovides less of a danger to birds, who will most probably not fly
into one. With a horizontal wind turbine, there is always the
chance that birds will fall foul of the machine, and therefore this
has another impact on the environment.
Problem with HAWT:
Tall HAWTs are difficult
to install, needing very
tall and expensive
cranes and skilled
operators.
Massive tower
construction is required
to support the heavy
blades, gearbox, and
generator.
Their height makes
them obtrusively visible
across large areas,
disrupting the
appearance of the
landscape and
sometimes creating
local opposition.
Downwind variants
suffer from fatigue and
structural failure
caused by turbulence
when a blade passes
through the tower's
wind shadow (for this
reason, the majority of
HAWTs use an upwind
design, with the rotor
facing the wind in front
of the tower).
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A VAWT that uses guy-wires to hold it in place puts stress on the bottom bearingas all the weight of the rotor is on the bearing. Guy wires attached to the top
bearing increase downward thrust in wind gusts. Solving this problem requires a
superstructure to hold a top bearing in place to eliminate the downward thrusts of
gust events in guy wired models.
The stress in each blade due to wind loading changes sign twice during eachrevolution as the apparent wind direction moves through 360 degrees. This
reversal of the stress increases the likelihood of blade failure by fatigue. While VAWTs' components are located on the ground, they are also located under
the weight of the structure above it, which can make changing out parts very
difficult without dismantling the structure, if not designed properly.
First, most of the turbines of this type only has an energy-producing capacitywhich is fifty percent less efficient than those produced by horizontal axis wind
turbines. Because there is no tower structure required, they cannot take full
advantage of the higher wind speeds that are available on higher, elevated
locations.
They also require energy to start the turning of blades due to their low startingtorque. They will have parts which are difficult to change without disassembling
the entire turbine should it not be assembled properly.
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There is no doubt that the Vertical axis windmills are a high speed device of
efficiency comparable to horizontal axis windmills.
It seems likely that this device will find use in the conversion of wind energy to
electric power especially if used on a large scale in conjunction with the grid.
In fact a 200 kW turbine driving a generator is at present being tested in Canada.
With such large devices it is quite feasible to have adequate control systems for
starting and controlling the system.
In India, however, the mean wind speeds are generally so low that it is unlikely
that wind power can be economically converted to electric power for grid augmentation.
The most practical use for wind power is likely to do direct water pumping for
drinking water and minor irrigation purposes.
The water pumping application generally implies high starting torque and low
control costs.
Hence it appears that Darrieus turbines arc not likely to be of much use in the
Indian context.
Single Phase Domestic Inverter is implemented and generated output near to sine
wave. SPWM technique reduces harmonic of generated output of Single Phase Domestic
Inverter which is required for Single Phase Domestic Electrical Appliances. SPWM
technique is difficult to implement but it requires less component, hence less costly and
viable for domestic use.
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Books
Electrical Machine Design of DHANPAT RAI & CO. by A.K.SAWHNEY. A text book of electrical technology (VOLUME 1) B.L. THERAJA &
A.K.THERAJA.
Engineering Electromagnetic ( SEVENTH EDITION) TATA McGraw HILL Power Electronics of Khanna Publisher by Dr. P.S. BIMBHRA. Muhammad Ali Mazidi, The 8051 Microconteroller and Embedded system,
2ndEddition.
Ramakangayakvad, Op-amps and linear integrated circuits
Websites
www.wikipedia.com/gps/index.shtml
www.datasheetcatalog.com
The Department of Energy, Utilities and Sustainability website at:
www.deus.nsw.gov.au/
The West wind Turbines website at: www.westwind.com.au/
The POWERCORP website at: www.pcorp.com.au/
The W.D. Moore & Co. website at: www.wdmoore.com.au/
The Country Energy website at: www.countryenergy.com.au/
The power-technology.com website at: www.power-technology.com
International Energy Agency website at: www.iea.org/
http://www.deus.nsw.gov.au/http://www.westwind.com.au/http://www.pcorp.com.au/http://www.wdmoore.com.au/http://www.countryenergy.com.au/http://www.power-technology.com/http://www.iea.org/http://www.iea.org/http://www.power-technology.com/http://www.countryenergy.com.au/http://www.wdmoore.com.au/http://www.pcorp.com.au/http://www.westwind.com.au/http://www.deus.nsw.gov.au/