
Esse link tem uma porção de dicas interessantes, para quem quer montar oficina, ou simplesmente converter seu veículo em casa. Ele usa um motor elétrico Siemens, que equipou Ford Ranger norte-americana, 1998 .
Apresentacao da pesquisa de todo o projeto de Graduacao em Engenharia mecanica Diego Meireles Lopes.
By Bill Moore, Editor, EVWORLD
MP3 audio interview with Edwin Black, author of Internal Combustion, on the electric car conspiracy.
Thomas Edison had spent $3.5 million between 1903 and 1910 (equivalent to $71 million today) perfecting his nickel iron battery. He claimed it was half the weight of lead acid and had twice the energy density. Electric cars equipped with it were demonstrably superior to the competition, which were powered by what we today know as Exide batteries, then controlled by a group of cartels, which sought to monopolize all forms of automotive transportation from bicycles to automobiles, gasoline and electric.
Just as Edison and Henry Ford were about to go into business together to offer a low cost electric car comparable to the Model T, a suspicious fire destroyed nearly all of Edison's West Orange, New Jersey research facility, curiously bypassing areas where the most flammable chemicals had been stored. Within months World War I would engulf Europe and eventually America and the dream of the electric car would fade into obscurity, a curious, forgotten footnote of history.
It would be Edwin Black, a best selling author whose works include IBM and the Holocaust, Banking on Baghdad and War Against the Weak, who would exhume the forgotten footnote and the overlooked collaboration between Edison and Ford in his 2006 investigative history into the conspiracy to kill the electric car nearly a century ago.
Black, who is as outspoken and unapologetic as his books, makes no bones about what attracted him to this story of turn of the 19th century avarice and corruption.
"Petro-terrorism."
He defines petro-terrorism as a movement whose intention is to "break down our society based on our addiction to oil." And while this particular form of coercion may seem like a relatively new phenomenon of the age of oil, Black asserts in Internal Combustion that it's as old as history, beginning with kingly control of the forests to monopolistic control of coal mines to today's modern oil cartels. The control of energy has been, in his words, the pursuit of monarchs, monopolists and manipulators from time immemorial.
Black takes pains to point out that his focus as an author is on exposing the grimy underbelly of society from IBM, Ford and General Motor's involvement in the rise of the Nazi Third Reich to the eugenics movement of early 20th century.
"I have a history of investigating genocide, oppression, corporate misconduct and governmental corruption," he emphasized.
For him, the never-solved, long-ignored fire in West Orange only serves to underscore his view that some conspiracies are quite real and in the case of the destruction of Edison's laboratory, the linchpin of a concerted effort to destroy the inventor's reputation in order to keep his battery off the market, while crushing Henry Ford at the same time.
Black weaves a compelling detective story that explains why the electric car failed despite its superiority as an urban transportation vehicle in an age when country roads were mud, suburbia didn't exist and gasoline was hard to find. Compared to the quiet, pollution free, dependable electric cars of the era, gasoline models were dirty, noisy and difficult to start, but that also gave them a certain machismo in the minds of the male motorist.
But beyond that, electric cars also were stigmatized in the minds of public of that day as the tool of corporate swindle artists from the "Lead Trust" to Carl Pope's bicycle monopoly to the automobile cartel, the latter buoyed by its lock on the infamous Selden patent, which Henry Ford fought against for a decade. It wouldn't be until 1911 that Ford would finally bust the Selden patent, though his company came perilously close to insolvency in its long legal battles in the courts.
In the context of the late 1890s and early 1900s, Black explained, electric car manufacturers were the 'bad guys', a complete reversal of where we are today which sees them as a means by which to save the planet.
"These were the Wall Street financiers, the bank manipulators, corporate raiders; and they decided to quash these internal combustion machine developers; names you'd now like Dodge and Cadillac."
Their legal instrument in this fight was George Selden's patent, which he'd acquired in the decades immediately after the American Civil War, and allegedly gave him the right to royalties on any and all automobiles built in America, if not the rest of the world. The patent was, in fact, nothing more than a simple line sketch, the kind of thing you'd draw on the back of an envelope or napkin. But with it, the cartel planned to intimidate and coerce its competitors with threats of expensive, protracted lawsuits.
Oddly at the time, the gasoline vehicle developers were the populists, Black said, but they would eventually join forces with the battery, electric car and bicycle cartels to form a super cartel, and in the process the electric car was abandoned in favor of the internal combustion machine.
"The one guy who would not [join] the cartel was Henry Ford. He did not want the internal combustion machine to be available for the rich man, the bank president and for the lawyer and for the doctor. He wanted the internal combustion machine to be available for all people as a kind of liberating American way of life. He was the populist.
"Now this is the same Henry Ford who ultimately became Adolf Hitler's hero, who I have investigated for his profound Nazi and anti-semetic activities, but the period in which I am writing Internal Combustion is years before that, a decade before that, perhaps two; and as a result, he is actually the hero of this book."
Before Ford won his legal battles against the Selden patent in 1911, anyone buying his car risked being sued by the cartel. So, along with a warranty, Ford also promised legal representation for its buyers.
With the downfall of the Selden patent, internal combustion cars began to proliferate, but it was also at that point, said Black, that Henry Ford realized that he had won the battle, but lost the war as the dirty, polluting cars spread at the expense of the far cleaner electric models.
So, he turned to Edison and together they quietly set about to develop an affordable electric car for the common man, one that could be charged off a cellar generator and residential-scale wind turbine, whose power would also be stored in Edison's NiFe battery.
Between 1912 and 1914, when the fire destroyed Edison's research complex, the two men tried vainly to perfect their car, but strangely, although the batteries worked fine in Edison's lab, by the time they reached Dearborn, they would fail, be damaged or simply not perform as specified.
Both Edison and Edwin Black suspected foul play.
Reading Internal Combustion you very quickly get a strong sense of déjà vu, that we've been here before, that in fact very little has changed, apart from some advances technologically.
As Black bluntly asserts, "We don't need to reinvent the wheel here. We need to exhume from where it was buried... a century ago. Whenever you get companies like General Motors who say we don't have a battery that works, or we're trying to make it work, there's new technology, it's all a lie. It's all a distraction because we know back in 1911 and 1912, the General Electric company had the Electrant, which was like a parking meter and when you parked in front of it, you plugged your electric car in and got a recharge. They had overnight charging facilities. Remember, there were no gas stations in 1911 and 1912. So, basically the idea was to recharge the battery."
On the topic of EV range, Black pointed out that some 75 percent of cars are driven about 25 miles a day, well within the capabilities of even Edison's century-old battery.
"There is no reason whatsoever that electric cars can't predominate today, except for the fact that the big automakers and the government that works with them are unwilling to undo decades of destructive automotive engineering, decades of oil addiction. It's not about... doing right for this world, right for this planet, right for our society; it's about keeping a lucrative status quo even as our climate changes, even as petro-terrorists and petro-politics put a gun to our head and a sword to our neck; and even as our American way of life and treasury is being transferred to the Middle East."
For Edwin Black, mobility is a human right, an entitlement from which everyone should be able to benefit.
"We must no longer be held hostage by those who want to control our ability to move from point 'A' to point 'B' and do so in a healthy, sensible fashion that will not make us subjugated to those in the Middle East."
One of the surprises for him personally while doing the research was the discovery of General Motors complicity in not only helping Hitler make blitzkrieg possible through its Germany subsidiary, Adam Opel, which it wholly acquired in 1931, but also its role in helping dismantle some 40 public trolley systems in cities across America.
"At the same time [they were wreaking havoc on the U.S. transit system] they were mobilizing the Third Reich to take over Europe and to destroy civilization. Remember it was General Motors that made the [Opel] Blitz truck for blitz kreig."
Black is equally outspoken about how little is being done to arrest the course we're on despite the rhetoric and the toying with EV technology.
"Bill, nothing is being done right!" he fairly shouted at me. "Nothing!"
"It doesn't matter if you and me and a million of our friends, every month throw out our gas guzzlers and convert to electric vehicles because if you and me and a million friends do that for a full year, there will still be 220 million gas guzzlers out on the road. You don't get it. The answer isn't one that you and I can solve," he asserted. "The only way that we can solve this is not through a government or any government, which has shown consistently for five thousand years that it will not follow a wise energy policy, it is my idea of the Green Fleet Initiative."
That initiative would see the huge numbers of fleet vehicles in both the public and private sector, some 28,000 strong, immediately begin converting over to electric drive and other alternative fuels. He cited commercial delivery fleets in the tens of thousands and the 100,000 taxis in the country, one third of which are replaced every year.
"If some or all of these fleets adopted a "Green Fleet Initiative" as I have outlined and say we will no longer buy any vehicle that isn't either an electric car or a hydrogen car or a biofuel car, excluding, of course, the big fake out which is corn ethanol. If some of these leading fleets said we'll drive our gas guzzlers into the ground and only replace them with these true alternative fuel vehicles, then the carmakers would beat each other to the starting line to be the first to sell en masse."
"People need to understand that we're not just going to have a picnic with the electric car if we're going fix the problem. We need to change the fleets; the millions of cars that are repaired, purchased and retired each year. The Post Office, the military, the university, the delivery company... And only when we start to do that will we truly address the problem.
"Answer me this, Why is it that Iran, facing sanctions, is now converting its entire automobile fleet within five years off of gasoline to compressed natural gas? What do they know that we don't know?
"We could move these cars off to compressed natural gas right now as a bridge technology to hydrogen cars; and remember hydrogen cars are electric vehicles," he stressed, pointing out that the fuel cell was first invested in the late 1830s.
"When is our government going to wake up?" he asked. "When are people going to demand that it makes no sense to send me a brochure about reducing carbon emissions if the company that delivered that brochure... helped kill our climate in the process, and kill our lungs in the process and kill our pocketbooks in the process and kill our way of life in the process?"
For all his fervency, Black admitted that he's not making much progress with his green fleet idea, though he believes that with a staff of six, he could make substantial headway by calling personally on fleet managers around the country.
"Everybody wants to talk about it; nobody wants to do it."
He would encourage people and companies to "ship green" and give a sort of Good Housekeeping seal of approval to companies who do. He also ridicules the the idea of carbon credits, comparing them to the selling of indulgences by the Catholic church during the Middle Ages.
"We need to stop right now, get on the phone and call the local sheriff, university, hospital, corporation and talk to the fleet manager... and ask them why their next 800,000 vehicles they buy, the next million vehicles they buy, the next ten vehicles they buy are not alternative fuel cars.
Black thinks that 18-year-long plans to improve vehicle mileage (fuel efficiency) is completely silly.
"Get off the better mileage dog and pony show. Who needs better mileage from a gas guzzler? Stop using those cars. When you get people trying to confuse the public with stories about petroleum reserves and stories about corn ethanol... Why is there a 54 cents [per gallon] penalty tax against Brazilian sugar cane ethanol, which is oil-free, and a 51 cents per gallon government subsidy for corn ethanol that goes right not to a farmer but to the oil companies?"
"We have to talk to our legislators. We have to get a grasp of what we're doing, and we're not going to have any ignition to this piston unless we know how we got addicted to oil and how to get off."
You can listen to the complete interview with Edwin Black by using the MP3 players at the top of the page or by downloading the file to your computer hard drive for transfer to your favorite MP3 player. His book, Internal Combustion, is available through Amazon.com and other fine book sellers.
http://books.google.com.br/books?id=E-T7ExPBvMwC&pg=PA158&dq=air+engi...
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A motor behaves as motor and as generator at the same time. In fact while a motor is 'motoring', that is doing mechanical work, it generates CEMF acting as generator, although the CEMF is lower than the battery voltage so the motor acts as a load and absorbs current.
In certain situations the CEMF may overcome the battery, in which case the generator component becomes dominant; the motor acts as a generator inverting the direction of its current and forcing it into the battery.
The typical situation is the one of a heavy vehicle rolling on a sharp downhill slope and forcing the motor to turn fast enough that the CEMF becomes larger than the battery voltage. As soon as the motor overcomes the battery it inverts the current direction and starts feeding current into the battery, while developing a counter torque that acts as a brake. This phase is called regeneration (recharging of the battery).
The Voltage/Current plane
Two wire DC electrical devices have one of the two poles marked as positive. By convention this is the pole where the positive voltage applied or generated is located.
These devices are divided into two categories:
The current is defined as positive if it enters the positive pole of a user, or exits the positive pole of a generator. See figure 1.
Obviously it is possible to force a negative current on the positive pole.
As an example, a common car battery (generator) sources a positive current (exiting the positive pole) when starting the car and sinks a negative current (entering the positive pole) while being recharged.
Similarly current can be made to exit from the positive pole of a resistor (user) inverting the voltage across it. By representing positive and negative voltage/current in a plane as a VI axis, we distinguish four quadrants.
As an example let's look at a car battery (figure 2); Q1 and Q 3 are the quadrants where the battery acts as a generator, since the current exits the positive pole. In Q1 the generator maintains a positive power rail while in Q3 the battery maintains a negative power rail.
Q2 and Q4 are the user quadrants, where the battery acts as a load to a battery charger that pushes current into the battery recharging it. In Q2 the battery charger output maintains a positive power rail, where in Q4 the charger maintains a negative power rail.
We will see shortly that a permanent magnet DC motor is also a four-quadrant device, acting as a user in Q1 and Q3, and as a generator in Q2 and Q4.
The only exception is for very large vehicles, where high power motors are needed, beyond the capability of permanent magnets, In this case a 'separately excited' motor is used, mostly the shunt version which, as long as the field winding is feed at constant voltage, behaves like a PM motor (constant flux).
In practice, since the shunt motor may malfunction should the field current accidentally become zero, what is used is a variation of the shunt motor called 'compound'. A small series field winding is added, to guarantee a minimum amount of field as long as there is armature current. An advantage of the shunt motor is that direction is reversed by reversing the field current, rather than the much larger armature current.
The interesting characteristics of the permanent magnet motor are:
From now on we refer exclusively to PM motors; they are widely used in many applications up to several HP.
As previously shown, a motor is a reversible machine; it acts in four quadrants of the Voltage/Current plane.
The motor can be assigned a positive pole, which corresponds to one of the two senses of rotation, for example the one moving a vehicle forward. Let's assume this is the clock-wise CW direction (Q1). Inverting the armature current inverts the direction, which becomes counter-clock-wise CW (Q3).
Q1 and Q3 are the quadrants where the motor is motoring, that is absorbing electrical energy and making mechanical work. Q2 and Q4 are the quadrants where the motor is generating, that are it is mechanically pulled, like for example by an electrical golf cart going downhill, and it acts as a DC generator.
It is useful to understand the equivalent circuit of a permanent motor. It is composed of a voltage generator equivalent to the Counter Electromotive Force CEMF, a series resistor equivalent to the resistance of the copper of the armature winding, and a series inductance.
The figure above shows the electrical equivalent circuit. The flux of the motor is constant so it is incorporated in the constant.
Note that torque is proportional to armature current and CEMF is proportional to the speed; the faster the motor turns, the higher is the CEMF. If the motor is turned by an external agent (gravity on a steep downhill) the CEMF can exceed the voltage of the battery and recharge it.
Energy balance in a vehicle
EK = ½MV2 where M is the mass and V is the speed (EQ 1)
EP = MgH where g = 9.8 m/sec2 is the gravity acceleration and H is the height (EQ 2)
ER = ½IW2 where I is the moment of inertia and W the angular velocity (EQ 3)
ER is normally very small and can be ignored (unless the vehicle is build on purpose with a heavy spinning wheel, such as boats using gyroscopic rotating masses for stabilization).
The total energy of the vehicle is:
Etot = EK + EP = M (½V2 + 10H) (EQ 4)
We have approximated gravity to 10 meter/second2.
A vehicle beginning an uphill slope will slow down losing kinetic energy (speed diminishes) while gaining potential energy (height increases). A vehicle beginning a downhill slope will lose potential energy (height decreases) and gain kinetic energy (speed increases).
A vehicle going over a summit with its motor disengaged will start moving downhill at constant acceleration until it will reach constant speed. This will happen when attrition and air resistance become sufficiently high to balance gravity. This is similar to a man parachuting who will initially fall at constant acceleration, until wind resistance will balance his speed and keep it constant.
A vehicle going over a summit with its motor engaged will behave in the same way, except that the motor will turn into a generator, effectively adding a braking effect to attrition and wind resistance so the vehicle will reach constant speed sooner and the speed will be lower.
Once the speed becomes constant, the kinetic energy remains constant; only the height decreases by a constant quantity over time. The delta Energy DEP is equal to:
DEP = 10M (H2 - H1) (EQ 5)
H2 is the initial and H1 is the final height. Let's assume in the last case for simplicity that attrition and wind resistance are negligible, then all the lost potential energy goes into the motor.
If we make the loss of altitude H2 - H12 equal to the loss in one second, then assuming the motor is connected to the battery, then the motor will transform in electrical power the lost Potential Energy per second.
Electrical Power = DEP = 10M (H2 - H1) (EQ 6)
Let's make an example.
A 300-kg electrical cart rolls downhill at a constant speed of 15 km/hour (about 10 mile/hour) on a 15% incline. Each second the cart covers four meters.
The loss of height per second is:
H2 - H1 = 4 x 0.15 = 0.6 meters. (EQ 7)
The loss of potential energy per second is:
DEP = 10 x 300 x 0.6 = 1,800 Joule per second (EQ 8)
In electrical terms this equates to 1.8 kW of electrical power.
The motor will generate an equivalent current (minus the generator efficiency), which will recharge the battery.
Coasting, Dynamic, Regenerative Braking
Let's assume we have an electric cart reaching a summit and then rolling downhill. As the cart passes the summit, the current in the motor drops to zero as no more torque is requested of the motor. The cart starts rolling downhill at constant acceleration, speeding up and forcing the motor to turn faster and faster so the CEMF increases until the motor turns fast enough that the CEMF exceeds the battery. At that moment the motor becomes a generator and the current will invert its direction and flow into the battery recharging it.
The motor, as generator, will develop a Counter Torque, (equivalent to the motor developing a CEMF) which will act as a brake. Eventually the Counter Torque and gravity will balance each other, at which point the cart will stop accelerating and will roll downhill at constant speed.
There are three ways a cart can be designed to handle a downhill:
Using a Power Supply
A battery is a two-quadrant generator, capable of issuing (discharge) or receiving (recharge) current at constant voltage.
A power supply in general is designed as a one-quadrant generator, designed for issuing current at constant voltage, but not for receiving it.
If a power supply has to be used, then the best choice is a conventional power supply with large filtering output electrolytic capacitors; a regenerating motor will charge the capacitors and as long as the voltage does not exceed their maximum rating, the power supply will operate in two quadrants. A switching power supply is in general not suitable.
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EK = ½MV2 where M is the mass and V is the speed (EQ 1)
EP = MgH where g = 9.8 m/sec2 is the gravity acceleration and H is the height (EQ 2)
ER = ½IW2 where I is the moment of inertia and W the angular velocity (EQ 3)
ER is normally very small and can be ignored (unless the vehicle is build on purpose with a heavy spinning wheel, such as boats using gyroscopic rotating masses for stabilization).
The total energy of the vehicle is:
Etot = EK + EP = M (½V2 + 10H) (EQ 4)
We have approximated gravity to 10 meter/second2.
A vehicle beginning an uphill slope will slow down losing kinetic energy (speed diminishes) while gaining potential energy (height increases). A vehicle beginning a downhill slope will lose potential energy (height decreases) and gain kinetic energy (speed increases).
A vehicle going over a summit with its motor disengaged will start moving downhill at constant acceleration until it will reach constant speed. This will happen when attrition and air resistance become sufficiently high to balance gravity. This is similar to a man parachuting who will initially fall at constant acceleration, until wind resistance will balance his speed and keep it constant.
A vehicle going over a summit with its motor engaged will behave in the same way, except that the motor will turn into a generator, effectively adding a braking effect to attrition and wind resistance so the vehicle will reach constant speed sooner and the speed will be lower.
Once the speed becomes constant, the kinetic energy remains constant; only the height decreases by a constant quantity over time. The delta Energy DEP is equal to:
DEP = 10M (H2 - H1) (EQ 5)
H2 is the initial and H1 is the final height. Let's assume in the last case for simplicity that attrition and wind resistance are negligible, then all the lost potential energy goes into the motor.
If we make the loss of altitude H2 - H12 equal to the loss in one second, then assuming the motor is connected to the battery, then the motor will transform in electrical power the lost Potential Energy per second.
Electrical Power = DEP = 10M (H2 - H1) (EQ 6)
Let's make an example.
A 300-kg electrical cart rolls downhill at a constant speed of 15 km/hour (about 10 mile/hour) on a 15% incline. Each second the cart covers four meters.
The loss of height per second is:
H2 - H1 = 4 x 0.15 = 0.6 meters. (EQ 7)
The loss of potential energy per second is:
DEP = 10 x 300 x 0.6 = 1,800 Joule per second (EQ 8)
In electrical terms this equates to 1.8 kW of electrical power.
The motor will generate an equivalent current (minus the generator efficiency), which will recharge the battery.
Coasting, Dynamic, Regenerative Braking
Let's assume we have an electric cart reaching a summit and then rolling downhill. As the cart passes the summit, the current in the motor drops to zero as no more torque is requested of the motor. The cart starts rolling downhill at constant acceleration, speeding up and forcing the motor to turn faster and faster so the CEMF increases until the motor turns fast enough that the CEMF exceeds the battery. At that moment the motor becomes a generator and the current will invert its direction and flow into the battery recharging it.
The motor, as generator, will develop a Counter Torque, (equivalent to the motor developing a CEMF) which will act as a brake. Eventually the Counter Torque and gravity will balance each other, at which point the cart will stop accelerating and will roll downhill at constant speed.
There are three ways a cart can be designed to handle a downhill:
Using a Power Supply
A battery is a two-quadrant generator, capable of issuing (discharge) or receiving (recharge) current at constant voltage.
A power supply in general is designed as a one-quadrant generator, designed for issuing current at constant voltage, but not for receiving it.
If a power supply has to be used, then the best choice is a conventional power supply with large filtering output electrolytic capacitors; a regenerating motor will charge the capacitors and as long as the voltage does not exceed their maximum rating, the power supply will operate in two quadrants. A switching power supply is in general not suitable. |
Speed is controlled by pulsating the Top MOS on one side of the bridge, while the Bottom MOS on the other side is always ON (PWM regulation); the speed will be proportional to the Duty Cycle of the PWM.
The Bottom MOS on the same side of the bridge of the Pulsating MOS is pulsated too in opposition to the Top MOS (the two must never be ON at the same time, or they will short the power supply with consequent damage to the controller).
The reason for pulsating the Bottom MOS is to provide a low resistance path to the inductive current of the motor, which is made safely re-circulate avoiding the typical high voltage spikes generated by an inductive load.
The Figure below illustrates the concept. At the top the Power Bridge is shown when the battery feeds the motor, and at the bottom when the motor re-circulates.
In the figure above both the controller and the motor have been conventionally assigned a positive pole, which for the controller corresponds to a positive current being generated and for the motor corresponds to the forward sense of rotation. Clearly this is a convention, as neither the controller nor the motors are in reality sold with a positive pole clearly marked.
Reversing the power bridge would reverse the sense of rotation of the motor, which would rotate backwards.
Less intuitive is the operation in the second and fourth quadrant, where the motor would generate current. To better understand this let's refer to the practical situation of a vehicle in motion.
A consequence of the motor current re-circulation is that the motor current is almost constant (effectively filtered by the inductance of the motor). Typically the inductance of a motor is a few millihenries while the internal resistance is at least 100 mΩ, so the time constant T = L/R is in at least 10 ms, much lager than the PWM frequency, hence the smoothing of the current into an almost DC current.
The figure below shows how the Power Bridge chops the battery current, while allowing the motor current to be DC. In essence the controller maintains the battery voltage constant and chops the battery current, while in turn chopping the motor voltage and maintaining constant the motor current.
Obviously the power generated by the battery must be equal to the power given to the motor (the controller has very high efficiency). Indicating the duty cycle as DC:
Power generated by the battery:
Vbb x Iaverage = Vbb x Ipeak x DC (EQ 9)
Power received by the motor: Imot x Vmot = Imot x Vbb x DC (EQ 10)
Therefore:
Vbb x Ipeak x DC = Imot x Vbb x DC (EQ 11)
Ipeak = Imot / DC (EQ 12)
As an example, measuring 5 A continuous current in the motor when the duty cycle is 10% means that the peak of current in the battery is 50 A, something to take into account in designing the mechanical and electrical power connections.
In reality, what is described above is not what is observed, since the current at the battery Ibb is close to a DC current, due to the smoothing effect of the of large electrolytic capacitors mounted in the controller.
Consequently the battery delivers a constant amount of power (constant voltage/constant current):
Pbb = Vbb x Ibb (EQ 13)
The motor conversely has its voltage Vbb chopped by the duty cycle DC and a constant current Imot; the two powers need to be the same, therefore:
Vbb x Ibb = (Vbb x DC) x Imot Imot = Ibb / DC (EQ 14)
In conclusion the current flowing in the motor is larger than the current measured at the battery except than when the duty cycle becomes 100%. The example above refers to the controller and the motor in the first quadrant.
Coming up in Part 2: The motor as a generator, the four quadrants, battery disconnect during regeneration and sizing the motor.
About the author:
Tony Santoni has a master's degree in electronics from the University of Rome, Italy. He is a partner in Roboteq and was formerly with STMicroelectronics in various management responsibilities, from Design to Sales. He presently lives and operates in Phoenix, AZ.
Este inversor conta com link CC para entrada direta de corrente contínua. Tem como características:
Entrada trifásica de 200-230V / 380-480V / 500-690V com variações de +10, -15%
Freqüência de saída: 0...204Hz (em rede de 60Hz) ou 0...170Hz (em rede de 50Hz). Acima de 204Hz (sob consulta).
A caixa em que ele é montado é bem ventilada mesmo para montagens em paineis.
A interface homem x máquina pode ser destacada do painel e via cabo ser operada à distância do inversor.
Também pode ser operado e parametrizado via software Superdrive da WEG.
Na foto abaixo vemos os pontos de ligação do inversor, onde 1, 2 e 3 são as fases de entrada (R,S e T), e 4, 5 e 6 as saídas para o motor trifásico (UVW).
Para inversão da rotação do motor sem fazer uso do inversor, basta trocar duas fases quaisquer do motor, de posição entre si (exemplo: U,V,W para W,V,U).
Este inversor aceita frenagem regenerativa, para tanto a carga deve ser ligada em 8 (BR) e 10 (veja foto acima). E conexão indutor (opcional) em 9 e 10 (no lugar do fio amarelo na foto acima). Para ligações do link CC basta conectar as baterias nos terminais 7 (-UD) e 9 acima. A correlação destes números da foto acima com o diagrama de bloco da foto abaixo é a seguinte: 10, 9, 8 e 7 acima são equivalentes respectivamente a 1, 2, 3 e 4 do diagrama abaixo:
Algumas características e parâmetros que considerei relevantes para uso em VEs dos inversroes da linha CFW-09:
O optimal Braking pode regenerar a carga para as baterias, supercapacitores, ou flywheel (mecânico), ao invés de dissipar a energia em um resistor.
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A curva de torque típica para um motor de indução trifásico:
Se usarmos um inversor para ir além da rotação nominal, o torque começa a cair depois dos 100% da rotação (frequência) nominal.
Como a curva de potência de um motor e dada pelo Torque x Rotação, a medida que a rotação aumenta, a potência aumenta também.
Até que atinge a rotação nominal do motor e ai a potência começa a ser quase constante, mesmo com a maior rotação do motor.
Uma curva de resposta bem interessante para um motor.
Com o uso de inversor, devido ao controle de U/F (ou V/F), ao se controlar a tensão e a freqüência, a curva do motor, pode ser deslocada com um torque menor na partida e limitação de sobre tensão.
Existe porém algum inconveniente do ponto de vista da elétrica em se deixar a tensão nominal na máxima e controlar apenas a freqüência?
Assim o gráfico da potência deveria ficar semelhante a linha verde do gráfico acima onde depois da rotação nominal a potência permaneceria quase constante com o aumento da rotação.
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Brasília, 25 de março de 2009
CONVITE
A Sua Senhoria o Senhor
Elifas Chaves Gurgel do Amaral
O Coordenador da Câmara Temática de Assuntos
Veiculares convida Vossa Senhoria para apresentar o Projeto de Veículo
Elétrico – conversão de veículo de motor à combustão para motor
elétrico, encaminhado ao Denatran pelo Processo nº
80001.034785/2008-17, na 20ª Reunião Ordinária da CTAV, agendada para
o dia 02 de abril de 2007, em Brasília.
Os carros novos vendidos no Brasil a partir de abril de 2009 terão uma etiqueta com informação sobre os níveis de consumo de combustível de cada veículo. A etiqueta faz parte do Programa Brasileiro de Etiquetagem Veicular, criado para apoiar o consumidor na hora de comprar um carro novo. O consumidor poderá decidir com mais informação entre a compra de um "beberrão" de combustível ou de um "mais eficiente", econômico e "respeitador do meio ambiente" para atender suas necessidades.
O programa é regulamentado pelo Instituto Nacional de Metrologia, Normalização e Qualidade Industrial (Inmetro), com a participação do Programa Nacional de Racionalização do Uso dos Derivados do Petróleo e do Gás Natural (Conpet), Petrobras, Ministério de Minas e Energia (MME), Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP), do Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis (Ibama), da Companhia de Tecnologia de Saneamento Ambiental de São Paulo (Cetesb) e conta com apoio da Associação Nacional dos Fabricantes de Veículos Automotores (Anfavea) e da Associação Brasileira de Empresas Importadoras de Veículos Automotivos (Abeiva).
A etiqueta
Os consumidores brasileiros poderão incluir em suas avaliaçôes na escolha dos veículos que irão adquirir a economia de combustível. A avaliação comparativa poderá ser feita mesmo entre combustíveis com características diferentes. Inicialmente, o programa vai abranger apenas os veículos leves movidos a gasolina, álcool e gás natural. Os veículos movidos a diesel, os pesados e as motocicletas, por enquanto, ficaram de fora da classificação, mas uma futura implantação da etiquetagem para esta frota não está descartada.
A Etiqueta Nacional de Conservação de Energia (Ence), que será afixada voluntariamente pelos fabricantes e importadores nos automóveis, apresentará os desempenhos com gasolina, etanol e GNV, tanto na estrada como em âmbito urbano. Conterá informações sobre a categoria de veículo, versão, motor e transmissão. Flechas coloridas apontarão a categoria de consumo do veículo, de A até E. A letra A representa os veículos de maior economia e a letra E os que consomem mais combustível.
Divulgado em maio, na Tailândia, o último estudo do 4º Relatório Mundial do Painel Intergovernamental sobre Mudanças Climáticas (IPCC) defendeu a utilização de veículos elétricos híbridos e a bateria para auxiliar na mitigação das mudanças climáticas e destacou, ainda, que a eficiência energética desempenha um papel importante neste cenário.
Quais as suas vantagens? |
A alta eficiência energética e o baixo ou quase nulo nível de emissões de poluentes e de ruídos, que resultam num impacto ambiental quase nulo, são as principais vantagens dos veículo elétricos para os convencionais. Além disso, estudos indicam que a eficiência global da eletricidade é pelo menos o dobro, por exemplo, da gasolina. |
Um levantamento detalhado da legislação do IPVA - Imposto sobre a Propriedade de Veículos Automotores revelou que há isenção desse imposto para os proprietários de vários tipos de veículos e para vários usos, tais como, máquinas agrícolas de terraplanagem e similares, ambulâncias, táxis, ônibus utilizados em transportes coletivos, veículos utilizados no combate a incêndio, veículos utilizados em transporte coletivo escolar e para deficientes físicos.
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