Short Circuits, Ground Faults and Ground Fault Circuit Interrupter

Posted by PITHOCRATES - April 9th, 2014

Technology 101

AC Power uses Reciprocating Currents to produce Rotating Electromagnetic Fields

There is a police crime lab television show that can solve a crime from a single fiber.  Many crime lab shows, actually.  Where they use high-tech science and music montages to solve many a crime.  Which is great if you DVR’d the shows as you can fast forward through them.  And save some time.  In one of these shows the writers goofed, though.  Because they didn’t understand the science behind the technology.

Someone murdered a construction worker by sabotaging a power cord.  By cutting off the grounding (or third) prong.  The fake crime scene person said this disabled the ground fault circuit interrupter (GFCI) device in the GFCI receptacle.  Leaving the user of the cord unprotected from ground faults.  So when said worker gripped the drill motor’s metallic case while standing in water and squeezed the trigger he got electrocuted.  And when the investigator saw that someone had cut off the grounding prong of the cord he said there was no way for the GFCI to work.  Which is, of course, wrong.  For the grounding prong has little to do with tripping the GFCI mechanism in a receptacle.

If you look at an electrical outlet you will see three holes.  Two vertical slots and one sort of round one.  Inside of these holes are pieces of metal that connect to wiring that runs back to the electric panel in your house.  One of the slots is the ‘hot’ circuit.  The other slot is the ‘neutral’ circuit.  And the third slot is the ‘ground’ circuit.  Now alternating current (AC) goes back and forth in the wiring.  It will come out of the hot and go into the neutral.  Then it will reverse course and come out of the neutral and go into the hot.  Think of a reciprocating engine where pistons go up and down to produce rotary motion.  AC current does the same to produce rotating electromagnetic fields in an electric motor.

The Current in our Electric Panels wants to Run to Ground

If the current can come out of both the hot and the neutral why aren’t both of these slotted holes hots?  Or both neutrals?  Good question.  The secondary winding on the pole-mounted transformer feeding your house has three wires coming from it.  The secondary is a very long wire wrapped many times around a core.  If you measure the voltage at both ends of this coil of wire you will get 240 volts.  They also attach a third wire to this coil of wire.  Right in the center of the coil.  So if you measure the voltage from this ‘center tap’ to one of the other two wires you will be measuring the voltage across half of the windings.  And get half of the voltage.  120 volts.

These are the three wires they bring into your house and terminate to your electric panel.  The center tap and the two wires coming off the ends of the secondary winding.  They attach each of the two ‘end wires’ to a hot bus bar in the panel.  And attach the center tap to the neutral bus.  They also connect the ground bus to the neutral bus.  A 1-pole circuit breaker attaches to one of the two hot bus bars.  Current travels along a wire attached to the breaker, runs through the house wiring, goes through the electrical load and back to the panel to the neutral bus.  So this back and forth current comes from the 120 voltage produced over half of the secondary coil of wire in the transformer.  Where as a 2-pole breaker attaches to both hot bus bars.  Current travels along a wire attached to one pole of the breaker, runs through the house wiring, through the electric load and back to the panel.  But instead of going to the neutral bus bar it goes to the other pole of the 2-pole breaker and to the other hot bus bar.  So this back and forth current comes from the 240 voltage produced across the whole secondary coil in the transformer.

Current wants to run to ground.  It’s why lightning hits trees.  Because trees are grounded.  The current in our electric panels wants to run to ground, too.  Which we only let it do after it does some work for us.  When we plug a cord into an electric outlet we are bringing the hot and neutral closer together.  Like when we plug in our refrigerator.   When the temperature falls a switch closes completing the circuit between hot and neutral through the compressor in the refrigerator.  So the current can run to ground.  Which is actually a back and forth motion through the conductors to create a rotating electromagnetic field in the compressor.  Which runs back and forth between one of the hot bus bars and the neutral bus bar in the panel.

Ground Faults don’t trip Circuit Breakers when finding an Alternate Path to Ground

When we stand on the ground we are grounded.  We are physically in contact with the ground.  We can lie on the ground and not get an electric shock.  Despite all current wanting to run to ground.  So if all current is running to ground why don’t we get a shock when we contact the ground?  Because we are at the same potential as the ground.  And no current flows between objects at the same potential (i.e., voltage).  This is the reason why we have a ground prong on our cords.  And why we install a bonding jumper between the neutral bus and the ground bus in our panels.  So that everything but the hot bus bars is at the same potential.  So no current flows through anything UNLESS that something is also connected to a wire running back to a hot bus in the panel.

Of course, if there is lightning outside we don’t want to be the tallest object out there.  For that lightning will find us to complete its path to ground.  Just as electricity will inside our house.  This is the purpose of the grounding prong on cords.  And why we ground all metallic components of things we plug into an electric outlet.  So if a hot wire comes loose inside of that thing and comes into contact with the metal case it will create a short circuit to ground for that current.  The current will be so great as it flows with no resistance that it will exceed the trip rating of the circuit breaker.  And open the breaker.  De-energizing everything in contact with that loose hot wire.  Eliminating an electric shock hazard.  For example, you could have a fluorescent light with a metal reflector in your basement.  It could have a loose hot wire that energizes the full metallic exterior of that light.  If you were working in the ceiling and had one hand on a cold water pipe when you came into contract with that light you would get a nasty electric shock.  But if it was grounded properly the breaker would trip before anyone could suffer an electric shock.

Ground faults are a different danger.  Because they don’t trip the circuit breaker in the panel.  Why?  Because it’s not a short circuit to ground.  But current taking a different path to ground.  That doesn’t end inside the electric panel.  For example, if you’re using a hair dryer in the bathroom you may come into contact with water and cold water piping.  Things that can conduct electricity to ground.  And if you are in contact with these alternate paths to ground some of that current in the hot wire will not equal the current in the neutral wire.  Because that back and forth current will be going in and out of the hot bus.  And in and out of a combination of the neutral bus and that alternate path to ground through you.  Electrocuting you.  But because of your body’s resistance the current flow through you will not exceed the breaker rating.  Allowing the current to keep flowing through you.  Perhaps even killing you.  This is why we have GFCI receptacles in our bathrooms, kitchens and anywhere else there may be an alternate path to ground.

So how does a GFCI work?  When current flows through a wire it creates an electromagnetic field around the wire.  If you’re looking into the wire as it runs away from you the field will be clockwise when the current is going away from you.  And counter clockwise when coming towards you.  In an AC circuit there are two conductors with current flow.  And at all times the currents are equal and run in opposite directions.  Cancelling those electromagnetic fields.  Unless there is a ground fault.  And if there is one the current in the neutral will decrease by the amount running to ground.  And the electromagnetic field in the neutral conductor will not cancel out the electromagnetic field in the hot conductor.  The GFCI will sense this and open the circuit.  Stopping all current flow.  Even if the ground prong was cut off.

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DC Power Supply

Posted by PITHOCRATES - February 13th, 2013

Technology 101

Every DC Power Supply has a Transformer, a Rectifier Circuit and a Voltage Regulation Circuit

Alternating current (AC) power is one of the greatest technological developments of mankind.  It gives us the modern world we live in.  We can transmit it over very long distances.  Allowing a few power plants to power large geographic areas.  Something Thomas Edison’s direct current (DC) power just couldn’t do.  Which is a big reason why he lost the War of Currents to George Westinghouse and Nikola Tesla.  AC power also allows the use of transformers.  Allowing us to take the one voltage produced by a power plant and convert it to any voltage we need.

AC power can power our home lighting.  Our air conditioning.  Our electric stove.  Our refrigerator.  Our doorbell.  Pretty much all of the non-fun things in our house.  Things with electric motors in them.  Heating elements.  Or solenoids.  But one thing AC power can’t do is power the fun things in our homes.  Televisions.  Our audio equipment.  Our cable/satellite boxes.  Pretty much anything that doesn’t have an electric motor, heating element or solenoid in it.  These things that process information or audio and video signals.  Or all of the above.  Things that have circuit boards.  With electronic components.  The kind of things that only work with DC power.

Of course all of these things in our homes plug into AC wall receptacles.  Even though they are DC devices.  So what gives?  How can we use AC power to operate DC devices?  With a little something we call a DC power supply.  And every one of those fun things has one.  Either one built-in.  Or an external power pack at the end of a cord.  Every DC power supply has three parts.  There is a transformer to step down the AC voltage.  A rectifier circuit.  And a voltage regulation circuit.

A Diode is a Semiconductor Device that allows a Current to pass through when there is a Forward Bias

The typical electrical receptacle in a house is 120 volt AC.  An AC power cord brings that into our electronic devices.  And the first thing it connects to is a transformer.  Such as a 120:24 volt transformer.  Which steps the 120 volts down to 24 volts AC.  Where the waveform looks like this.

DC Power Supply AC Input

The voltage of AC power rises and falls.  It starts at zero.  Rises to a maximum positive voltage.  Then falls through zero to a maximum negative voltage.  Then rises back to zero.  This represents one cycle.  It does this 60 times a second.  (In North America, at least.  In Europe it’s 50 times a second.)  As most electronic devices are made from semiconductors this is a problem.  For semiconductor devices use low DC voltages to cause current to flow through PN junctions.  A voltage that swings between positive and negative values would only make those semiconductor devices work half of the time.  Sort of like a fluorescent light flickering in the cold.  Only these circuits wouldn’t work that well.  No, to use these semiconductors we need to first get rid of those negative voltages.  By rectifying them to positive voltages.  When we do we get a waveform that looks like this.

DC Power Supply Rectified

A diode is a semiconductor device that allows a current to pass through when there is a forward bias.  And it blocks current from passing through when there is a reverse bias.  An alternating voltage across a diode alternates the bias back and forth between forward bias and reverse bias. Using one diode would produce a waveform like in the first graph above only without the negative parts.  If we use 4 diodes to make a bridge rectifier we can take those negative voltages and make them positive voltages.  Basically flipping the negative portion of the AC waveform to the positive side of the graph.  So it looks like the above waveform.

All Electronic Devices have a Section built Inside of them called a Power Supply

The rectified waveform is all positive.  There are no negative voltages.  But the voltage is more of a series of pulses than a constant voltage.  Varying between 0 and 24 volts.  But our electronic devices need a constant voltage.  So the next step is to smooth this waveform out a little.  And we can do this by adding a capacitor to the output of the bridge rectifier.  Which sort of acts like a reservoir.  It stores charge at higher voltages.   And releases charge at lower voltages.  As it does it smooths out the waveform of our rectified voltage.  Making it less of a series of pulses and more of a fluctuating voltage above and below our desired output voltage.  And looks sort of like this.

DC Power Supply Capacitor

This graph is exaggerated a little to show clearly the sinusoidal waveform.  In reality it may not fluctuate quite so much.  And the lowest voltage would not fall below the rated DC output of the DC power supply.  Please note that now we have a voltage that is always positive.  And never zero.  As well as fluctuating in a sinusoidal waveform at twice the frequency of the original voltage.  The last step in this process is voltage regulation.  Another semiconductor device.  Typically some transistors forming a linear amplifier.  Or an integrated circuit with three terminals.  An input, an output and a ground.  We apply the above waveform between the input and ground.  And these semiconductor devices will change voltage and current through the device to get the following output voltage (for a 12 volt DC power supply).

DC Power Supply DC Output

All electronic devices that plug into a wall outlet with a standard AC power cord have a section built inside of them called a power supply.  (Or there is an external power supply.  Small ones that plug into wall outlets.  Or bigger ones that are located in series with the power cord.)  And this is what happens inside the power supply.  It takes the 120 volt AC and converts it to 12 volts DC (or whatever DC voltage the device needs).  Wires from this power supply go to other circuit boards inside these electronic devices.  Giving the electronic components on these circuit boards the 12 volt DC power they need to operate.  Allowing us to watch television, listen to music or surf the web.

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Electric Power, Alternating Current, Transformers, Magnetic Flux, Turns Ratio, Electric Panel and Circuit Breakers

Posted by PITHOCRATES - February 6th, 2013

Technology 101

AC Power is Superior to DC Power because it can Travel Farther and it Works with Transformers

Thanks to Nikola Tesla and his alternating current electric power we live in the world we have today.  The first electric power was direct current.  The stuff that Thomas Edison gave us.  But it had some serious drawbacks.  You needed a generator for each voltage you used.  The low-voltage of telephone systems would need a generator.  The voltage we used in our homes would need another generator.  And the higher voltages we used in our factories and businesses would need another generator.  Requiring a lot of power cables to hang from power poles along our streets.  Almost enough to block out the sun.

Another drawback is that direct currents travel a long way.  And spend a lot of time moving through wires.  Generating heat.  And dropping some power along the way due to the resistance in the wires.  Greatly minimizing the area a power plant can provide power to.  Requiring many power plants in our cities and suburbs.  Just imagine having three coal-fired power plants around your neighborhood.  The logistics and costs were just prohibitive for a modern electric world.  Which is why Thomas Edison lost the War of Currents to Nikola Tesla.

So why is alternating current (AC) superior to direct current (DC) for electric power?  AC is more like a reciprocating motion in an internal combustion engine or a steam locomotive.  Where short up & down and back & forth motion is converted into rotation motion.  Alternating current travels short distances back and forth in the power cables.  Because they travel shorter distances in the wires they lose less power in power transmission.  In fact, AC power lines can travel great distances.  Allowing power plants tucked away in the middle of nowhere power large geographic areas.  But there is another thing that makes AC power superior to DC power.  Transformers.

The Voltage induced onto the Secondary Windings is the Primary Voltage multiplied by the Turns Ratio

When an alternating current flows through a coiled wire it produces an alternating magnetic flux.  Magnetic flux is a measure of the strength and concentration of the magnetic field created by that current.  When this flux passes through another coiled wire it induces a voltage on that coil.  This is a transformer.  A primary and secondary winding where an alternating current applied on the primary winding induces a voltage on the secondary winding.  Allowing you to step up or step down a voltage.  Allowing one generator to produce one voltage.  While transformers throughout the power distribution network can produce the many voltages needed for doorbells, electrical outlets in our homes and the equipment in our factories and businesses.  And any other voltage for any other need.

We accomplish this remarkable feat by varying the number of turns in the windings.  If the number of turns is equal in the primary and the secondary windings then so is the voltage.  If the number of turns in the primary windings is greater than the number of turns in the secondary windings the transformer steps down the voltage.  If the number of turns in the secondary windings is greater than the number of turns in the primary windings the transformer steps up the voltage.  To determine the voltage induced onto the secondary windings we divide the secondary turns by the primary turns.  Giving us the turns ratio.  Multiplying the turns ratio by the voltage applied to the primary windings gives us the voltage on the secondary windings.  (Approximately.  There are some losses.  But for the sake of discussion assume ideal conditions.)

If the turns ratio is 20:1 it means the number of turns on the primary windings is twenty times the turns on the secondary windings.  Which means the voltage on the primary windings will be twenty times the voltage on the secondary windings.  Making this a step-down transformer.  So if you connected 4800 volts to the primary windings the voltage across the secondary windings will be 240 volts (4800/20).  If you attached a wire to the center of the secondary coil you can get both a 20:1 turns ratio and a 40:1 turns ratio.  If you measure a voltage across the entire secondary windings you will get 240 volts.  If you measure from the center of the secondary and either end of the secondary windings you will get 120 volts.

The Power Lines running to your House are Two Insulated Phase Conductors and a Bare Neutral Conductor

This is a common transformer you’ll see atop a pole in your backyard.  Where it is common to have 4800-volt power lines running at the top of poles running between houses.  On some of these poles you will see a transformer mounted below these 4800-volt lines.  The primary windings of these transformers connect to the 4800-volt lines.  And three wires from the secondary windings connect to wires running across these poles below the transformers.  Two of these wires (phase conductors) connect to either end of the secondary windings.  Providing 240 volts.  The third wire attaches to the center of the secondary windings (the neutral conductor).  We get 120 volts between a phase conductor and the neutral conductor.

The power lines running to your house are three conductors twisted together in a triplex cable.  Two insulated phase conductors.  And a bare neutral conductor.  These enter your house and terminate in an electric panel.  The two phase conductors connect to two bus bars inside the panel.  The neutral conductor connects to a neutral bus inside the panel.  Each bus feeds circuit breaker positions on both sides of the panel.  The circuit breaker positions going down the left side of the panel alternate between the two buss bars.  Ditto for the circuit breaker positions on the right side.

A single-pole circuit breaker attaches to one of the bus bars.  Then a wire from the circuit breaker and a wire from the neutral bus leave the panel and terminate at an electrical load.  Providing 120 volts to things like wall receptacles where you plug things into.  And your lighting.  A 2-pole circuit breaker attaches to both bus bars.  Then two wires from the circuit breaker leave the panel and attach to an electrical load.  Providing 240 volts to things like an electric stove or an air conditioner.  Then a reciprocating (push-pull) alternating current runs through these electric loads.  Driven by the push-pull between the two bus bars.  And between a bus bar and the neutral bus.  Which is driven by the push-pull between the conductors of the triplex cable.  Driven by the push pull of secondary windings in the transformer.  Driven by the push-pull of the primary windings.  Driven by the push-pull in the primary cables connected to the primary windings.  And all the way back to the push-pull of the electric generator.  All made possible thanks to Nikola Tesla.  And his alternating current electric power.

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The Horse, Waterwheel, Steam Engine, Electricity, DC and AC Power, Power Transmission and Electric Motors

Posted by PITHOCRATES - December 26th, 2012

Technology 101

(Original published December 21st, 2011)

A Waterwheel, Shaft, Pulleys and Belts made Power Transmission Complex

The history of man is the story of man controlling and shaping our environment.  Prehistoric man did little to change his environment.  But he started the process.  By making tools for the first time.  Over time we made better tools.  Taking us into the Bronze Age.  Where we did greater things.  The Sumerians and the Egyptians led their civilization in mass farming.  Created some of the first food surpluses in history.  In time came the Iron Age.  Better tools.  And better plows.  Fewer people could do more.  Especially when we attached an iron plow to one horsepower.  Or better yet, when horses were teamed together to produce 2 horsepower.  3 horsepower.  Even 4 horsepower.  The more power man harnessed the more work he was able to do.

This was the key to controlling and shaping our environment.  Converting energy into power.  A horse’s physiology can produce energy.  By feeding, watering and resting a horse we can convert that energy into power.  And with that power we can do greater work than we can do with our own physiology.  Working with horse-power has been the standard for millennia.  Especially for motive power.  Moving things.  Like dragging a plow.  But man has harnessed other energy.  Such as moving water.  Using a waterwheel.  Go into an old working cider mill in the fall and you’ll see how man made power from water by turning a wheel and a series of belts and pulleys.  The waterwheel turned a main shaft that ran the length of the work area.  On the shaft were pulleys.  Around these pulleys were belts that could be engaged to transfer power to a work station.  Where it would turn another pulley attached to a shaft.  Depending on the nature of the work task the rotational motion of the main shaft could be increased or decreased with gears.  We could change it from rotational to reciprocating motion.  We could even change the axis of rotation with another type of gearing.

This was a great step forward in advancing civilization.  But the waterwheel, shaft, pulleys and belts made power transmission complex.  And somewhat limited by the energy available in the moving water.  A great step forward was the steam engine.  A large external combustion engine.  Where an external firebox heated water to steam.  And then that steam pushed a piston in a cylinder.  The energy in expanding steam was far greater than in moving water.  It produced far more power.  And could do far more work.  We could do so much work with the steam engine that it kicked off the Industrial Revolution.

Nikola Tesla created an Electrical Revolution using AC Power

The steam engine also gave us more freedom.  We could now build a factory anywhere we wanted to.  And did.  We could do something else with it, too.  We could put it on tracks.  And use it to pull heavy loads across the country.  The steam locomotive interconnected the factories to the raw materials they consumed.  And to the cities that bought their finished goods.  At a rate no amount of teamed horses could equal.  Yes, the iron horse ended man’s special relationship with the horse.  Even on the farm.  Where steam engines powered our first tractors.  Giving man the ability to do more work than ever.  And grow more food than ever.  Creating greater food surpluses than the Sumerians and Egyptians could ever grow.  No matter how much of their fertile river banks they cultivated.  Or how much land they irrigated.

Steam engines were incredibly powerful.  But they were big.  And very complex.  They were ideal for the farm and the factory.  The steam locomotive and the steamship.  But one thing they were not good at was transmitting power over distances.  A limitation the waterwheel shared.  To transmit power from a steam engine required a complicated series of belts and pulleys.  Or multiple steam engines.  A great advance in technology changed all that.  Something Benjamin Franklin experimented with.  Something Thomas Edison did, too.  Even gave us one of the greatest inventions of all time that used this new technology.  The light bulb.  Powered by, of course, electricity.

Electricity.  That thing we can’t see, touch or smell.  And it moves mysteriously through wires and does work.  Edison did much to advance this technology.  Created electrical generators.  And lit our cities with his electric light bulb.  Electrical power lines crisscrossed our early cities.  And there were a lot of them.  Far more than we see today.  Why?  Because Edison’s power was direct current.  DC.  Which had some serious drawbacks when it came to power transmission.  For one it didn’t travel very far before losing much of its power. So electrical loads couldn’t be far from a generator.  And you needed a generator for each voltage you used.  That adds up to a lot of generators.  Great if you’re in the business of selling electrical generators.  Which Edison was.  But it made DC power costly.  And complex.  Which explained that maze of power lines crisscrossing our cities.  A set of wires for each voltage.  Something you didn’t need with alternating current.  AC.  And a young engineer working for George Westinghouse was about to give Thomas Edison a run for his money.  By creating an electrical revolution using that AC power.  And that’s just what Nikola Tesla did.

Transformers Stepped-up Voltages for Power Transmission and Stepped-down Voltages for Electrical Motors

An alternating current went back and forth through a wire.  It did not have to return to the electrical generator after leaving it.  Unlike a direct current ultimately had to.  Think of a reciprocating engine.  Like on a steam locomotive.  This back and forth motion doesn’t do anything but go back and forth.  Not very useful on a train.  But when we convert it to rotational motion, why, that’s a whole other story.  Because rotational motion on a train is very useful.  Just as AC current in transmission lines turned out to be very useful.

There are two electrical formulas that explain a lot of these developments.  First, electrical power (P) is equal to the voltage (V) multiplied by the current (I).  Expressed mathematically, P = V x I.  Second, current (I) is equal to the voltage (V) divided by the electrical resistance (R).  Mathematically, I = V/R.  That’s the math.  Here it is in words.  The greater the voltage and current the greater the power.  And the more work you can do.  However, we transmit current on copper wires.  And copper is expensive.  So to increase current we need to lower the resistance of that expensive copper wire.  But there’s only one way to do that.  By using very thick and expensive wires.  See where we’re going here?  Increasing current is a costly way to increase power.  Because of all that copper.  It’s just not economical.  So what about increasing voltage instead?  Turns out that’s very economical.  Because you can transmit great power with small currents if you step up the voltage.  And Nikola Tesla’s AC power allowed just that.  By using transformers.  Which, unfortunately for Edison, don’t work with DC power.

This is why Nikola Tesla’s AC power put Thomas Edison’s DC power out of business.  By stepping up voltages a power plant could send power long distances.  And then that high voltage could be stepped down to a variety of voltages and connected to factories (and homes).  Electric power could do one more very important thing.  It could power new electric motors.  And convert this AC power into rotational motion.  These electric motors came in all different sizes and voltages to suit the task at hand.  So instead of a waterwheel or a steam engine driving a main shaft through a factory we simply connected factories to the electric grid.  Then they used step-down transformers within the factory where needed for the various work tasks.  Connecting to electric motors on a variety of machines.  Where a worker could turn them on or off with the flick of a switch.  Without endangering him or herself by engaging or disengaging belts from a main drive shaft.  Instead the worker could spend all of his or her time on the task at hand.  Increasing productivity like never before.

Free Market Capitalism gave us Electric Power, the Electric Motor and the Roaring Twenties

What electric power and the electric motor did was reduce the size and complexity of energy conversion to useable power.  Steam engines were massive, complex and dangerous.  Exploding boilers killed many a worker.  And innocent bystander.  Electric power was simpler and safer to use.  And it was more efficient.  Horses were stronger than man.  But increasing horsepower required a lot of big horses that we also had to feed and care for.  Electric motors are smaller and don’t need to be fed.  Or be cleaned up after, for that matter.

Today a 40 pound electric motor can do the work of one 1,500 pound draft horse.  Electric power and the electric motor allow us to do work no amount of teamed horses can do.  And it’s safer and simpler than using a steam engine.  Which is why the Roaring Twenties roared.  It was in the 1920s that this technology began to power American industry.  Giving us the power to control and shape our environment like never before.  Vaulting America to the number one economic power of the world.  Thanks to free market capitalism.  And a few great minds along the way.

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Electric Grid, Voltage, Current, Power, Phase Conductor, Neutral Conductor, 3-Phase Power, Transmission Towers and Corona Discharge

Posted by PITHOCRATES - August 15th, 2012

Technology 101

The Electric Grid is the Highways and Byways for Electric Power from the Power Plant to our Homes

Even our gasoline-powered cars operate on electricity.  The very thing that ignites the air-fuel mixture is an electric spark.  Pushed across an air-gap by a high voltage.  Because that’s something that high voltages do.  Push electrons with such great force that they can actually leave a conductor and travel through the air to another conductor.  Something we don’t want to happen most of the time.  Unless it’s in a spark plug in our gasoline engine.  Or in some movie prop in a cheap science fiction movie.

No.  When we use high voltage to push electrons through a conductor the last thing we want to happen is for the electrons to leave that conductor.  Because we spend a pretty penny to push those electrons out of a power plant.  And if we push the electrons out of the conductor they won’t do much work for us.  Which is the whole point of putting electricity into the electric grid.  To do work for us.

The electric grid.  What exactly is it?  The highways and byways for electric power.  Power plants produce electric power.  And send it to our homes.  As well as our businesses.  Power is the product of voltage and current.  In our homes something we plug into a 120V outlet that draws 8 amps of current consumes 960 watts.  Which is pretty big for a house.  But negligible for a power plant generator producing current at 20,000 volts.  For at 20,000 volts a generator only has to produce 0.48 amps (20,000 X 0.48 = 960).  Or about 6% of the current at 120V.

Between our Homes and the Power Plant we can Change that Current by Changing the Voltage

Current is money.  Just as time is money.  In fact current used over time helps to determine your electric bill.  Where the utility charges you for kilowatt hours (voltage X current X time).  (This would actually give you watt-hours.  You need to divide by 1000 to get kilowatt hours.)  The electric service to your house is a constant voltage.  So it’s the amount of current you use that determines your electric bill.  The more current you use the greater the power you use.  Because in the power equation (voltage X current) voltage is constant while current increases.

Current travels in conductors.  The size of the conductor determines a lot of costs.  Think of automobile traffic.  Areas that have high traffic volumes between them may have a very expensive 8-lane Interstate expressway interconnecting them.  Whereas a lone farmer living in the ‘middle of nowhere’ may only have a much less expensive dirt road leading to his or her home.  And so it is with the electric grid.  Large consumers of electric power need an Interstate expressway.  To move a lot of current.  Which is what actually spins our electrical meters.  Current.  However, between our homes and the power plant we can change that current.  By changing the voltage.  Thereby reducing the cost of that electric power Interstate expressway.

The current flowing through our electric grid is an alternating current.  It leaves the power plant.  Travels in the conductors for about 1/120 of a second.  Then reverses direction and heads back to the power plant.  And reverses again in another 1/120 of a second.  One complete cycle (travel in both directions) takes 1/60 of a second.  And there are 60 of these complete cycles per second.  Hence the alternating current.  If you’re wondering how this back and forth motion in a wire can do any work just think of a steam locomotive.  Or a gasoline engine.  Where a reciprocating (back and forth) motion is converted into rotational motion that can drive a steam locomotive.  Or an automobile.

The Voltages of our Electric Grid balance the Cost Savings (Smaller Wires) with the Higher Costs (Larger Towers)

An electric circuit needs two conductors.  When current is flowing away from the power plant in one it is flowing back to the power plant in the other.  As the current changes direction is has to stop first.  And when it stops flowing the current is zero.  Using the power formula this means there are zero watts twice a cycle.  Or 120 times a second.  Which isn’t very efficient.  However, if you bring two other sets of conductors to the work load and time the current in them properly you can remove these zero-power moments.  You send the first current out in one set of conductors and wait 1/3 of a cycle.  Then you send the second current out in the second set of conductors and wait another 1/3 cycle.  Then you send the third current out in the third set of conductors.  Which guarantees that when a current is slowing to stop to reverse direction there are other currents moving faster towards their peak currents in the other conductors.  Making 3-phase power more efficient than single-phase power.  And the choice for all large consumers of electric power.

Anyone who has ever done any electrical wiring in their home knows you can share neutral conductors.  Meaning more than one circuit coming from your electrical panel can share the return path back to the panel.  If you’ve ever been shocked while working on a circuit you switched off in your panel you have a shared neutral conductor.  Even though you switched off the circuit you were working on another circuit sharing that neutral was still switched on and placing a current on that shared neutral.  Which is what shocked you.  So if we can share neutral conductors we don’t need a total of 6 conductors as noted above.  We only need 4.  Because each circuit leaving the power plant (i.e., phase conductor) can share a common neutral conductor on its way back to the power plant.  But the interesting thing about 3-phase power is that you don’t even need this neutral conductor.  Because in a balanced 3-phase circuit (equal current per phase) there is no current in this neutral conductor.  So it’s not needed as all the back and forth current movement happens in the phase conductors.

Electric power travels in feeders that include three conductors per feeder.  If you look at overhead power lines you will notice they all come in sets of threes when they get upstream of the final transformer that feeds your house.  The lines running along your backyard will have three conductors across the top of the poles.  As they move back to the power plant they pass through additional transformers that increase their voltage (and reduce their current).  And the electric transmission towers get bigger.  With some having two sets of 3-conductor feeders.  The higher the voltage the higher off the ground they have to be.  And the farther apart the phase conductors have to be so the high voltage doesn’t cause an arc to jump the ‘air gap’ between phase conductors.  As you move further away from your home back towards the power plant the voltage will step up to values like 2.4kV (or 2,400 volts), 4.8kV and13.2kV that will typically take you back to a substation.  And then from these substations the big power lines head back towards the power plant.  On even bigger towers.  At voltages of 115kV, 138kV, 230kV, 345kv, 500kV and as high as 765kV.  When they approach the power plant they step down the voltage to match the voltage produced by its generators.

They select the voltages of our electric grid to balance the cost savings (smaller wires) with the higher costs (larger towers taking up more land).  If they increase the voltage so high that they can use very thin and inexpensive conductors the towers required to transmit that voltage safely may be so costly that they exceed the cost savings of the thinner conductors.  So there is an economic limit on voltage levels  As well as other considerations of very high voltages (such as corona discharge where high voltages create such a power magnetic field around the conductors that it may ionize the air around it causing a sizzling sound and a fuzzy blue glow around the cable.  Not to mention causing radio interference.  As well as creating some smog-causing pollutants like ozone and nitrogen oxides.)

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Conservation of Energy, Potential Energy, Kinetic Energy, Waterwheels, Water Turbine, Niagara Falls, Dams, and Hydroelectric Power

Posted by PITHOCRATES - July 25th, 2012

Technology 101

Roller Coasters use Gravity to Convert Energy back and forth between Potential Energy and Kinetic Energy

We cannot destroy energy.  All we can do is convert it.  It’s a law of physics.  The law of conservation of energy.  A roller coaster shows this.  Where roller coasters move by converting potential energy into kinetic energy.  And then by converting kinetic energy back into potential energy.

The best roller coasters race down tall inclines gaining incredible speed.  The taller the coaster the faster the speed.  That’s because of potential energy (stated in units of joules).  Which is equal to the mass times the force of gravity times the height.  The last component is what makes tall roller coasters fast.  Height.  As the cars inch over the summit gravity begins pulling them down.  And the longer gravity can pull them down the more speed they can gain.  At the bottom of the hill the height is zero so the potential energy is zero.  All energy having been converted into kinetic energy (also stated in units of joules).

Roller coasters travel the fastest at the lowest points in the track.  Where potential energy equals zero.  While kinetic energy is at its highest.  Which is equal to one half times the mass times the velocity squared.  So the higher the track the more time gravity has to accelerate these cars.  At their fastest speed they start up the next incline.  Where the force of gravity begins to pull on them.  Slowing them down as they climb up the next hill.  Converting that kinetic energy back into potential energy.  When they crest the hill for a moment their speed is zero so their kinetic energy is zero.  All energy having been converted back into potential energy.  Where gravity tugs those cars down the next incline.  And so on up and down each successive hill.  Where at all times the sum of potential energy and kinetic energy equals the same amount of joules.  Maximum potential energy is at the top.  Maximum kinetic energy is at the bottom.  And somewhere in the middle they each equal half of their maximum amounts.

(This is a simplified explanation.  Additional forces are ignored for simplicity to illustrate the relation between potential energy and kinetic energy.)

We build Dams on Rivers  to do what Niagara Falls does Naturally

So once over the first hill roller coasters run only on gravity.  And the conversion of energy from potential to kinetic energy and back again.  Except for that first incline.  Where man-made power pulls the cars up.  Electric power.  Produced by generators.  Spun by kinetic energy.  Produced from the expanding gases of combustion in a natural gas-powered plant.  Or from high-pressure steam produced in a coal-fired power plant or nuclear power plant.  Or in another type of power plant that converts potential energy into kinetic energy.  In a hydroelectric dam.

Using water power dates back to our first civilizations.  Then we just used the kinetic energy of a moving stream to turn a waterwheel.  These waterwheels turned shafts and pulleys to transfer this power to work stations.  So they couldn’t spin too fast.  Which wasn’t a problem because people only used rivers and streams with moderate currents.  So these wheels didn’t spin fast.  But they could turn a mill stone.  Or run a sawmill.  With far more efficiency than people working with hand tools.  But there isn’t enough energy in a slow moving river or stream to produce electricity.  Which is why we built some of our first hydroelectric power plants at Niagara Falls.  Where there was a lot of water at a high elevation that fell to a lower elevation.  And if you stick a water turbine in the path of that water you can generate electricity.

Of course, there aren’t Niagara Falls all around the country.  Where nature made water fall from a high elevation to a low elevation.  So we had to step in to shape nature to do what Niagara Falls does naturally.  By building dams on rivers.  As we blocked the flow of water the water backed up behind the dam.  And the water level climbed up the river banks to from a large reservoir.  Or lake.  Raising the water level on one side of the dam much higher than the other side.  Creating a huge pool of potential energy (mass times gravity times height).  Just waiting to be converted into kinetic energy.  To drive a water turbine.  The higher the height of the water behind the dam (or the higher the head) the greater the potential energy.  And the greater the kinetic energy of the water flow.  When it flows.

Hydroelectric Power is the Cleanest and Most Reliable Source of Renewable Energy-Generated Power

Near the water level behind the dam are water inlets into channels through the dam or external penstocks (large pipes) that channels the water from the high elevation to the low elevation and into the vanes of the water turbine.  The water flows into these curved vanes which redirects this water flow down through the turbine.  Creating rotational motion that drives a generator.  After exiting the turbine the water discharges back into the river below the dam.

Our electricity is an alternating current at 60 hertz (or cycles per second).  These turbines, though, don’t spin at 60 revolutions per second.  So to create 60 hertz they have to use different generators than they use with steam turbines.  Steam turbines spin a generator with only one rotating magnetic field to induce a current in the stator (i.e., stationary) windings of the generator.  They can produce an alternating current at 60 hertz because the high pressure steam can spin these generators at 60 revolutions per second.  The water flowing through a turbine can’t.  So they add additional rotational magnetic fields in the generator.  Twelve rotational magnetic fields can produce 60 hertz of alternating current while the generator only spins at 5 revolutions per second.  Adjustable gates open and close to let more or less water to flow through the turbine to maintain a constant rotation.

The hydroelectric power plant is one of the simplest of power generating plants.  There is no fuel needed to generate heat to make steam.  No steam pressure to monitor closely to prevent explosions.  No fires to worry about in the mountains of coal stored at a plant.  No nuclear meltdown to worry about.  And no emissions.  All you need is water.  From snow in the winter that melts in the spring.  And rain.  Not to mention a good river to dam.  If the water comes the necessary head behind the dam will be there to spin those turbines.  But sometimes the water isn’t there.  And the dams have to shut down generators because there isn’t enough water.  But hydroelectric power is still the cleanest and most reliable source of electric power generated from renewable energy we have.  But it does have one serious drawback.  You need a river to dam.  And the best spots already have a dam on them.  Leaving little room for expansion of hydroelectric power.  Which is why we generate about half of our electric power from coal.  Because we can build a coal-fired power plant pretty much anywhere we want to.  And they will run whether or not we have snow or rain.  Because they are that reliable.

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Windmills, Rotational Energy, Wing, Lift, Rotary Wing, Angle of Attack, Variable-Pitch Propellers, Drag, AC Power and Wind Turbine

Posted by PITHOCRATES - June 27th, 2012

Technology 101

When an Aircraft Rotates for Takeoff it increases the Angle of Attack of the Wing to Create more Lift

Early windmills turned when the wind pushed a sail or vane.  Thereby converting wind energy into rotational energy.  Mechanical linkages and shafts transferred this rotational motion to power a mill.  Or pump water.  As well as an assortment of other tasks.  Whatever the task it was important to regulate the speed at which the shaft rotated.  Which meant turning the windmill into the wind.  And adjusting the amount of sail catching the wind.  Much like on a sailing ship.  At first by shutting the windmill down and manually adjusting the sails.  Then later automating this process while the windmill was turning.  If the winds were too strong they’d lock the windmill to prevent it from turning.  To prevent damaging the windmill.

They regulated the speed to protect the equipment attached to the windmill, too.  To prevent a mill stone from spinning too fast.  Risking damage to it.  And harm to the people working with the equipment.  Or to protect a water pump form pumping too fast.  Even the small farm windmills had over-speed protection.   These sat atop a well.  The windmill drove a small piston to pump the water up the well shaft.  To prevent this windmill from flying apart in high winds over-speed features either furled the blades or rotated the windmill parallel to the wind.  Shutting the pump down.

But wind just doesn’t push.  It can also lift.  A lateen (triangular) sail on a sailing vessel is similar to an aircraft wing.  The leading edge of the sail splits the wind apart.  Part of it fills the sail and pushes it.  Bowing it out into a curved surface.  The wind passing on the other side of the sail travels across this curved surface and creates lift.  Similar to how a wing operates during takeoff on a large aircraft.  With the trailing edge flaps extended it creates a large curve in the wing.  When the aircraft rotates (increasing the angle of attack of the wing) to take off wind passing under the wing pushes it up.  And the wind travelling over the wing pulls it up.  These lift forces are so strong that planes carry their fuel in the wings and mount engines on the wing to keep the wings from bending up too much from these forces of lift.

A Pilot will Feather the Propeller on a Failed Engine in Flight to Minimize Drag 

When an aircraft carrier launches its aircraft it turns into the wind.  To maximize the wind speed travelling across the wings of the aircraft.  For the faster the wind moves across the wing the great lift it creates.  Commercial airports don’t have the luxury of turning into the wind.  So they lay their runways out to correspond to the prevailing wind directions.  As weather systems move through the region they often reverse the direction of the wind.  When they do planes take off in the other direction.  If the winds are somewhere in between these two extremes some airports have another set of runways called ‘crosswind’ runways.  Or trust in the highly skilled pilots flying out of their airports to adjust the control surfaces on their planes quickly and delicately to correct for less than optimal winds.

Helicopters don’t have this problem.  They can take off facing in any direction.  Because that big propeller on top is a rotary wing.  Or rotor.  A fixed wing airplane needs forward velocity to move air over their wings to create lift.  A helicopter moves air over its rotary wing by spinning it through the air.  To create lift the pilot tilts the rotor blades to change their angle of attack.  And tilts the whole rotor in the direction of travel.  The helicopter’s engine runs at a constant RPM.  To increase lift the angle of attack is increased.  This also creates drag that increases the load on the engine, slowing it down.  So the pilot increases the throttle of the engine to return the rotor to that constant RPM.

Propeller-powered airplanes also have variable-pitch propellers.  To create the maximum possible lift at the lowest amount of drag.  So it’s not just engine speed determining aircraft speed.  When running up the engines while on the ground the pilot will feather the propellers.  So that the blade pitch is parallel to the airflow and moves no air.  This allows the engines to be run up to a high RPM without producing a strong blast of air behind it.  A pilot will also feather the prop on a failed engine in flight to minimize drag.  Allowing a single-engine plane to glide and a multiple engine plane to continue under the power of the remaining engines.  A pilot can even reverse the pitch of the propeller blades to reverse the direction of airflow through the propeller.  Helping planes to come to a stop on short runways.

By varying the Blade Pitch for Different Wind Speeds Wind Turbines can Maintain a Constant RPM

Thomas Edison developed DC electrical power.  George Westinghouse developed AC electrical power.  And these two went to war to prove the superiority of their system.  The War of the Currents.  Westinghouse won.  Because AC is economically superior.  One power plant can power a very large geographic area.  Because alternating current (AC) works with transformers.  Which stepped up voltages for long-distance power transmission.  And then stepped them back down to the voltages we use.  Power equals voltage times current.  Increasing the voltages allows lower currents.  Which allows thinner wires.  And fewer generating plants.  Which saves money.  Hence the economic superiority of AC power.

Alternating current works with transformers because the current alternates directions 60 times a second (or 60 cycles or hertz).  Every time the currents reverse an electrical field collapses in one set of windings of a transformer, inducing a voltage in another set of windings.  A generator (or, alternator) creates this alternating current by converting rotational energy into electrical energy.  Which brings us back to windmills.  A source of rotational energy.  Which we can also use to generate electrical energy.  But unlike windmills of old, today’s windmills, or wind turbines, turn from lift.   The wind doesn’t push the blades.  The wind passes over them producing lift.  Like on a wing.  Pulling them into rotation.

The typical wind turbine design is a three-bladed propeller attached to a nacelle sitting on top of a tall pylon.  The nacelle is about as large as a big garden shed or a small garage.  Inside the nacelle are the alternator and a gearbox.  And various control equipment.  Like windmills of old wind turbines still have to face into the wind.  We could do this easily and automatically by placing the propeller on the downwind side of the nacelle.  Making it a weathervane as well.  But doing this would put the pylon between the wind and the blades.  The pylon would block the wind causing uneven loading on the propeller producing vibrations and reducing the service life.  So they mount the propeller on the upwind side.  And use a complex control system to turn the wind turbine into the wind.

When it comes to electrical generation a constant rotation is critical.  How does this happen when the wind doesn’t blow at a constant speed?  With variable-pitched blades on the propeller.  By varying the blade pitch for different wind speeds they can maintain a constant number of revolutions per minute (RPM).  For a limited range of wind conditions, that is.  If the wind isn’t fast enough to produce 60 hertz they shut down the wind turbine.  They also shut them down in high winds to prevent damaging the wind turbine.  They can do this by feathering the blades.  Turning the propeller blades parallel to the wind.  Or with a mechanical brake.  The actual rotation of the propeller is not 60 cycles per second.  But it will be constant.  And the gearbox will gear it up to turn the alternator at 60 cycles per second.  Allowing them to attach the power they produce to the electric grid.

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Thomas Edison, Patents, Intellectual Property Rights, Nikola Tesla, George Westinghouse, DC, AC and the War of Currents

Posted by PITHOCRATES - March 27th, 2012

History 101

Thomas Edison protected his Intellectual Property Rights with over 1,000 Patents

Thomas Edison was a great inventor.  A great entrepreneur.  But he wasn’t a great scientist or engineer.  He was home-schooled by his mom.  And didn’t go to college.  But he read a lot.  And loved to tinker.  He grew up in Port Huron, Michigan.  At one end of the train line that ran between Port Huron and Detroit.  Where he sold newspapers and other things to commuters during the Civil War.  Then he saved the life of some kid.  Pulled him out of the way of a runaway boxcar.  The kid’s dad ran the train station.  Out of gratitude for saving his son’s life he taught the young Edison Morse Code.  And trained him to be a telegraph operator.  He mastered it so well that Edison invented a better telegraph machine.  The Quadruplex telegraph.  Because he liked to tinker.

What made him a great entrepreneur and not a great scientist or engineer is that his inventions had a commercial purpose.  He didn’t invent to solve life’s great mysteries.  He invented to make money.  By creating things so great that people would want them.  And pay money for them.  He also had an eye on production costs.  So he could build these things the people wanted at affordable prices.  For if they were too expensive the people couldn’t buy them.  And make him rich.  So his inventions used technology to keep production costs down while keeping consumer interest high.  Because of the profit incentive.  But the POSSIBILITY of profits wasn’t enough to push Edison to set up his invention lab.  Where he employed a team of inventors to work full time inventing things.  And figuring out how to mass-produce inventions that made everyone’s life better.  He needed something else.  Something that GUARANTEED Edison could profit from his inventions.  The patent.  That gave the patent holder exclusive rights to profit from their invention.

Inventors and entrepreneurs spend a lot of money inventing things.  They do this because they know that they can file a patent when they invent something that people will buy.  Protecting their intellectual property rights.  So they alone can profit from the fruit of all their labors.  And Edison was one of these inventors.  One of the most prolific inventors of all time.  Filing over 1,000 patents.  Including one on the incandescent light bulb.  Which was going to replace gas lamps and candles.  And provided a need for another new invention.  Electric power distribution.  Something else he spent a lot of time tinkering with.  Producing electrical generators.  And an electric power distribution system.  Which was going to make him an even richer man.  As he held the patents for a lot of the technology involved.  However, he was not to become as rich as he had hoped on his electric power distribution system.  Not for any patent infringements.  But because of a mistreated former employee who had a better idea.

Thomas Edison and George Westinghouse battled each other in the War of Currents

Nikola Tesla was a brilliant electrical engineer.  But not a great entrepreneur.  So he worked for someone who was.  Thomas Edison.  Until Edison broke a promise.  He offered a substantial bonus to Tesla if he could improve Edison’s electric power generating plants.  He did.  And when he asked for his bonus Edison reneged on his promise.  Telling the immigrant Tesla that he didn’t understand American humor.  Angry, Tesla resigned and eventually began working for George Westinghouse.  An Edison competitor.  Who appreciated the genius of Tesla.  And his work.  Especially his work on polyphase electrical systems.  Using an alternating current (AC).  Unlike Edison’s direct current (DC).  Bringing Edison and Tesla back together again.  In war.

Direct current had some limitations.  The chief being that DC didn’t work with transformers.  While AC did.  With transformers you could change the voltage of AC systems.  You could step the voltage up.  And step it back down.  This gave AC a huge advantage over DC.  Because power equals current multiplied by voltage (P=I*E).  To distribute large amounts of power you needed to generate a high current.  Or a high voltage.  Something both DC and AC power can do.  However, there is an advantage to using high voltages instead of high currents.  Because high currents need thicker wires.  And we make wires out of copper or aluminum.  Which are expensive.  And the DC wires have to get thicker the farther away they get from the generator plant.  Meaning that a DC generating plant could only serve a small area.  Requiring numerous DC power plants to meet the power requirements of a single city.  Whereas AC power could travel across states.  Making AC the current of choice for anyone paying the bill to install an electric distribution system.

So the ability to change voltages is very beneficial.  And that’s something DC power just couldn’t do.  What the generator generated is what you got.  Not the case with AC power.  You can step it up to a higher voltage for distribution.  Then you can step it down for use inside your house.  Which meant a big problem for Edison.  For anyone basing their decision on price alone would choose AC.  So he declared war on AC power.  Saying that it was too dangerous to bring inside anyone’s house.  And he proved it by electrocuting animals.  Including an elephant.  And to show just how lethal it was Edison pushed for its use to replace the hangman’s noose.  Saying that anything as deadly as what states used to put prisoners to death was just too deadly to bring into anyone’s house.  But not even the electric chair could save Edison’s DC power.  And he lost the War of Currents.  For Tesla’s AC power was just too superior to Edison’s DC power not to use. 

Nikola Tesla was a Brilliant Engineer who Preferred Unraveling the Mysteries of the Universe over Business

George Westinghouse would get rich on electrical distribution.  Thanks to Nikola Tesla.  And the patents for the inventions he could have created for Thomas Edison.  If he only recognized his genius.  Which he lamented near death as his greatest mistake.  Not appreciating Tesla.  Or his work.  But Edison did well.  As did Westinghouse.  They both died rich.  Unlike Tesla.

Westinghouse could have made Tesla a very rich man.  But his work in high voltage, high frequency, wireless power led him away from Westinghouse.  For he wanted to provide the world with free electric power.  By creating power transmitters.  That could transmit power wirelessly.  Where an electric device would have an antenna to receive this wireless power.  He demonstrated it to some potential investors.  He impressed them.  But lost their funding when they asked one question.  Where does the electric meter go?  Free electric power was a noble idea.  But nothing is truly free.  Even free power.  Because someone had to generate that power.  And if you didn’t charge those using that power how were you going to pay those generating that power?

Edison and Westinghouse were great entrepreneurs.  Whereas Tesla was a brilliant engineer.  He preferred unraveling the mysteries of the universe over business.  Tesla probably suffered from obsessive-compulsive disorder.  Think of the character Sheldon Cooper on The Big Bang Theory television sitcom.  He was a lot like that character.  Brilliant.  Odd.  And interested in little else but his work.  He lived alone.  And died alone.  A bachelor.  Living in a two-room hotel room in the last decade of his life.  Despite his inventions that changed the world.  And the fortunes he made for others.  Sadly, Tesla did not die a rich man.  Like Edison and Westinghouse.  But he did live a long life.  And few men or women changed the world like he did.  A brilliant mind that comes around but once in a millennium.

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The Horse, Waterwheel, Steam Engine, Electricity, DC and AC Power, Power Transmission and Electric Motors

Posted by PITHOCRATES - December 21st, 2011

Technology 101

A Waterwheel, Shaft, Pulleys and Belts made Power Transmission Complex

The history of man is the story of man controlling and shaping our environment.  Prehistoric man did little to change his environment.  But he started the process.  By making tools for the first time.  Over time we made better tools.  Taking us into the Bronze Age.  Where we did greater things.  The Sumerians and the Egyptians led their civilization in mass farming.  Created some of the first food surpluses in history.  In time came the Iron Age.  Better tools.  And better plows.  Fewer people could do more.  Especially when we attached an iron plow to one horsepower.  Or better yet, when horses were teamed together to produce 2 horsepower.  3 horsepower.  Even 4 horsepower.  The more power man harnessed the more work he was able to do.

This was the key to controlling and shaping our environment.  Converting energy into power.  A horse’s physiology can produce energy.  By feeding, watering and resting a horse we can convert that energy into power.  And with that power we can do greater work than we can do with our own physiology.  Working with horse-power has been the standard for millennia.  Especially for motive power.  Moving things.  Like dragging a plow.  But man has harnessed other energy.  Such as moving water.  Using a waterwheel.  Go into an old working cider mill in the fall and you’ll see how man made power from water by turning a wheel and a series of belts and pulleys.  The waterwheel turned a main shaft that ran the length of the work area.  On the shaft were pulleys.  Around these pulleys were belts that could be engaged to transfer power to a work station.  Where it would turn another pulley attached to a shaft.  Depending on the nature of the work task the rotational motion of the main shaft could be increased or decreased with gears.  We could change it from rotational to reciprocating motion.  We could even change the axis of rotation with another type of gearing.

This was a great step forward in advancing civilization.  But the waterwheel, shaft, pulleys and belts made power transmission complex.  And somewhat limited by the energy available in the moving water.  A great step forward was the steam engine.  A large external combustion engine.  Where an external firebox heated water to steam.  And then that steam pushed a piston in a cylinder.  The energy in expanding steam was far greater than in moving water.  It produced far more power.  And could do far more work.  We could do so much work with the steam engine that it kicked off the Industrial Revolution.

Nikola Tesla created an Electrical Revolution using AC Power

The steam engine also gave us more freedom.  We could now build a factory anywhere we wanted to.  And did.  We could do something else with it, too.  We could put it on tracks.  And use it to pull heavy loads across the country.  The steam locomotive interconnected the factories to the raw materials they consumed.  And to the cities that bought their finished goods.  At a rate no amount of teamed horses could equal.  Yes, the iron horse ended man’s special relationship with the horse.  Even on the farm.  Where steam engines powered our first tractors.  Giving man the ability to do more work than ever.  And grow more food than ever.  Creating greater food surpluses than the Sumerians and Egyptians could ever grow.  No matter how much of their fertile river banks they cultivated.  Or how much land they irrigated.

Steam engines were incredibly powerful.  But they were big.  And very complex.  They were ideal for the farm and the factory.  The steam locomotive and the steamship.  But one thing they were not good at was transmitting power over distances.  A limitation the waterwheel shared.  To transmit power from a steam engine required a complicated series of belts and pulleys.  Or multiple steam engines.  A great advance in technology changed all that.  Something Benjamin Franklin experimented with.  Something Thomas Edison did, too.  Even gave us one of the greatest inventions of all time that used this new technology.  The light bulb.  Powered by, of course, electricity.

Electricity.  That thing we can’t see, touch or smell.  And it moves mysteriously through wires and does work.  Edison did much to advance this technology.  Created electrical generators.  And lit our cities with his electric light bulb.  Electrical power lines crisscrossed our early cities.  And there were a lot of them.  Far more than we see today.  Why?  Because Edison’s power was direct current.  DC.  Which had some serious drawbacks when it came to power transmission.  For one it didn’t travel very far before losing much of its power. So electrical loads couldn’t be far from a generator.  And you needed a generator for each voltage you used.  That adds up to a lot of generators.  Great if you’re in the business of selling electrical generators.  Which Edison was.  But it made DC power costly.  And complex.  Which explained that maze of power lines crisscrossing our cities.  A set of wires for each voltage.  Something you didn’t need with alternating current.  AC.  And a young engineer working for George Westinghouse was about to give Thomas Edison a run for his money.  By creating an electrical revolution using that AC power.  And that’s just what Nikola Tesla did.

Transformers Stepped-up Voltages for Power Transmission and Stepped-down Voltages for Electrical Motors

An alternating current went back and forth through a wire.  It did not have to return to the electrical generator after leaving it.  Unlike a direct current ultimately had to.  Think of a reciprocating engine.  Like on a steam locomotive.  This back and forth motion doesn’t do anything but go back and forth.  Not very useful on a train.  But when we convert it to rotational motion, why, that’s a whole other story.  Because rotational motion on a train is very useful.  Just as AC current in transmission lines turned out to be very useful.

There are two electrical formulas that explain a lot of these developments.  First, electrical power (P) is equal to the voltage (V) multiplied by the current (I).  Expressed mathematically, P = V x I.  Second, current (I) is equal to the voltage (V) divided by the electrical resistance (R).  Mathematically, I = V/R.  That’s the math.  Here it is in words.  The greater the voltage and current the greater the power.  And the more work you can do.  However, we transmit current on copper wires.  And copper is expensive.  So to increase current we need to lower the resistance of that expensive copper wire.  But there’s only one way to do that.  By using very thick and expensive wires.  See where we’re going here?  Increasing current is a costly way to increase power.  Because of all that copper.  It’s just not economical.  So what about increasing voltage instead?  Turns out that’s very economical.  Because you can transmit great power with small currents if you step up the voltage.  And Nikola Tesla’s AC power allowed just that.  By using transformers.  Which, unfortunately for Edison, don’t work with DC power.

This is why Nikola Tesla’s AC power put Thomas Edison’s DC power out of business.  By stepping up voltages a power plant could send power long distances.  And then that high voltage could be stepped down to a variety of voltages and connected to factories (and homes).  Electric power could do one more very important thing.  It could power new electric motors.  And convert this AC power into rotational motion.  These electric motors came in all different sizes and voltages to suit the task at hand.  So instead of a waterwheel or a steam engine driving a main shaft through a factory we simply connected factories to the electric grid.  Then they used step-down transformers within the factory where needed for the various work tasks.  Connecting to electric motors on a variety of machines.  Where a worker could turn them on or off with the flick of a switch.  Without endangering him or herself by engaging or disengaging belts from a main drive shaft.  Instead the worker could spend all of his or her time on the task at hand.  Increasing productivity like never before.

Free Market Capitalism gave us Electric Power, the Electric Motor and the Roaring Twenties

What electric power and the electric motor did was reduce the size and complexity of energy conversion to useable power.  Steam engines were massive, complex and dangerous.  Exploding boilers killed many a worker.  And innocent bystander.  Electric power was simpler and safer to use.  And it was more efficient.  Horses were stronger than man.  But increasing horsepower required a lot of big horses that we also had to feed and care for.  Electric motors are smaller and don’t need to be fed.  Or be cleaned up after, for that matter.

Today a 40 pound electric motor can do the work of one 1,500 pound draft horse.  Electric power and the electric motor allow us to do work no amount of teamed horses can do.  And it’s safer and simpler than using a steam engine.  Which is why the Roaring Twenties roared.  It was in the 1920s that this technology began to power American industry.  Giving us the power to control and shape our environment like never before.  Vaulting America to the number one economic power of the world.  Thanks to free market capitalism.  And a few great minds along the way.

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