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Know Your Engines-Electric Motor

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posted on Mar, 27 2006 @ 10:49 PM

Can this thing change the world?
This electric motor, and it’s scaled up brothers and sisters, has the potential to replace the internal combustion engine as oil reserves dwindle and research into alternative energies increases. The electric motor is deceivingly simple, and has in fact been around longer than the internal combustion engine.
The first electric ‘motors’ were credited to Michael Faraday in 1821(hSource). They were little more than demonstration platforms of the technique of electromagnetism. The engines have proceeded from crude little demonstrations to efficient machines that we find everywhere- oufans, computers, kitchens, cars, radios, even our cute little robotic dogs. We rely upon them.
As I said before, electric motors are deceivingly simple. Whereas in an internal combustion engine, you can see the explosions, pressures, openings and closings, an electric motor works through forces you have to imagine –namely- electricity, magnetism, and chemistry. I will not cover every type of electric motor, only ones that directly relate to the spirit of this forum, engines which may some day power your cars. That said, let’s get some work done.

The heart of an electric motor is the electromagnet. Electromagnets are little more than wire wrapped around a piece of metal, with a current running throughout. How does that work? Well, the answer lies at the root of electromagnetism-a force that pervades the universe. All you need to know for this is electromagnetism states that electricity and magnetism cannot exist without the other.
A circuit that has a current flowing through it will create a magnetic field around the wires. This is due to a property of electromagnetism- the electric field shifts as the electricity moves through the wire, inducing a magnetic field as a byproduct. Likewise, a spinning magnet placed near a circuit will induce a current (which is the basis of energy generation, from coal plants to fusion plants)
What you need to know concerning electric motors is that a wire with an electric current will create a magnetic field, and the best way to utilize that field is to twist the wire carrying the circuit into a circle. The classic example of why this is necessary is a length of copper wire twisted around a nail. Now, connecting the two wires on either side of the magnet to a battery will let a current flow through the wire, inducing magnetism. Since the wire is coiled around in circles, the field is concentrated. Generally speaking- More and more tightly coiled wires will increase the strength of the magnet along with an increase in voltage.
With the wires connected and charged, the nail will develop a north and south side, just like a magnet. These will be found at the head and the tip, and depend on which wire is touching the positive (+) end of the battery and which is touching the negative (-) end. Say the head is north and the tip is south. Flip the polarity of the wires, and the head will become south while the tip is now north.
Now, we all know the basics of magnetism-South repels south and attracts north, while north repels north and attracts south. This is the basis for the second part of an electric motor. Imagine that your electromagnet nail is in the middle of a horseshoe magnet. Connect the battery, and the nail will align itself accordingly, north to south and south to north. Quickly reverse the polarity of the battery, and the nail will flip so that it is again aligned correctly. Those are the basics of a DC electric motor


What you see above is a head on view of a small electric motor. The metal circle in the middle is the axle. The three metal bits with wire wrapped about them are three electromagnets, collectively called the armature. The larger circle around the motor represents the container and permanent magnets (earth magnets which require no power source to operate).
Now, three armatures is the minimum number of electromagnets you should have in a motor. As you can imagine, the nail would not make an effective motor because it “balances out” the electric field and maintains its position. Having at least three electromagnets of shifting polarity will keep the motor “unbalanced” so that it never becomes stuck.
How does the polarity of the magnets keep shifting? Well, through a little something engineers like to call commutator. If you look in the back of a motor, you’ll see the two wires entering on opposite sides, one + and one -. On the interior of the motor, each wire has a “paddle” or “brush”, made of a durable and springy metal. This DC motor has a “commutator” on the armature, which looks like a round bit of metal with a break in the middle.
The commutator spins within the brushes, staying in contact with the brushes. Each side of the commutator is the beginning or end of a circuit through the electromagnet. As the magnet spins, the brushes hit the break in the commutator, and momentum carries the commutator on to the opposite brush. This reverses the polarity just in time to keep the engine moving.

The motor described above is a DC motor, and is best served in very low-speed, high-torque jobs. Examples are your electric car antennae, your CD player, toys, and the like. They are also used in forklifts, elevators, most notably golf carts.
For a good animation of a DC motor, see Here

The next, and most important, motor that concerns this thread is the AC (or AC induction) Motor. While an AC motor is most likely to be inside an Electric Vehicle (EV), the DC motor is also found there sometimes because of lower cost. As you will see later, the AC induction motor is the superior, regardless of cost (Think CRT vs. 100" flat screen HDTV)
The most popular and powerful of the AC motors is the Three-phase Induction motor. The construction and operation of an AC motor is slightly different from the DC motor, to say the least. Being but a business student, I had trouble wrapping my mind around these concepts. I’m going to save you the trouble of pursuing the different niches of motors, and present to you the most common AC motor around, the one that will likely power your car someday.

This is a Three Phase Induction motor.
The “Three Phase” portion of the name refers to the type of power that operates the motor, while “Induction” describes how the motor operates. Very generally, the electromagnets are on the outside (stator), while the rotor (rotor) sits inside. The rotor itself is comprised of a cylindrical “cage” of either aluminum or copper set into grooves of the Iron core, and connected at the end by a large ring. The nickname for this type of rotor is the “squirrel cage” rotor, due to its likeness of a hamster wheel. I know. Engineers.

The three-phase induction motor begins by firing the electromagnets situated around the rotor in a three-phase electrical sequence. Now, I’m no engineer. I’m writing this up, and fact checking it again and again as much for my own benefit as yours. To this end, I spent hours slugging through mathematics, engineer-speak, and complex diagrams before stumbling upon two diagrams that finally allowed me to make sense of three-phase energy.



Now, the first image shows the different wirings of the three-phase engine’s electromagnets. For my own sake, I’ll say that this means there are three different wires leading to the three electromagnets.
Now, this is possible through three phase electrical power. You don’t need to know extensive math, or know that three phase power is used for high voltage transportation (Ok, you do need to know that it’s able to handle high volts-that’s because the high voltage is spread across three lines, but essentially do the same job. Three lines carrying 10,000 volts are equal to 30,000 volts. If you tried to carry that on the same line, you get into resistance and other engineering things. I’m trying to keep this simple, and the power needs to be carried across three lines)
By looking at the three phases graph, you can see that there is never a moment when all three magnets will be completely off or on. This means that there will be a “leading” magnet that pulls or pushes the motor in its direction, respective to the rise or fall of the current. All other magnets will carry on in their respective rises and falls at the same time. Through three lines, different lines. This is as far as I can go with my meager brain.
Now that that is out of the way, this is what happens: The rotor within the electromagnets is “induced” into movement because of the rotating magnetic field produced by the three-phase system going on. Depending on the load that is placed upon the motor, the rotor will lag behind the field by a certain amount. This is called the “slip” of the engine.

There are many reasons why a three-phase induction motor is suited for operating an automobile.
-Regenerative braking: Already in use on hybrid vehicles, in fact, this feature half defines hybrid vehicles. In traditional cars, pushing the brakes pushes the brake pads down on the wheels, slowing them down by converting motion to heat through friction. With regenerative braking, the brakes are connected to the ac motor, converting the motion of the wheels to the magnets, inducing an electric charge, which is sent to the batteries (remember the basis of electromagnetism). In a hybrid car, the engine kicks in to give an extra burst of energy while accelerating, taking the burden off the gasoline engine.
-Electronic reverse (DC engines require customization to run in reverse)
-Adapt characteristics of the motor via software
-Lack of brushes (In a DC motor, the brushes are liable to arc high voltage electricity at high RPM)
-High RPM limit (~10,000)
-Water cooled
-Highly reliable

Okay. Well. That is the first, and most important part of an electrical vehicle, and we are finished with it. There are three more parts to consider. These are the Batteries, AC Inverter, and Power Source.

Batteries- The batteries are the main power source for an EV. The most common battery is a lead-acid battery. Now, car batteries, and almost all batteries for that matter, operate through chemistry. I will keep this simple because anyone who has been through a high school chemistry class knows the basics, and those who haven’t will soon enough.
Two diodes are placed inside an acidic solution. The acid breaks apart the diodes and itself in the process. Depending on the materials used, you will have x number of electrons move towards the positive diode. At this point the battery can be attached to your car, or “stacked” with other batteries to increase the voltage or amplitude.
In either case, every battery that is used in a car must have the ability to be reversed. Adding electricity to the diodes will replace the electrons and force the diodes and acidic solution back to their starting position. Here is a quick list of battery types. In EV, the key is to get a great power-to-weight ratio, while keeping the cost as low as possible. Remember, batteries only last a number of years, and must be replaced, and easily become the most expensive part of an EV’s lifespan.

* Zinc-carbon battery - Also known as a standard carbon battery, zinc-carbon chemistry is used in all inexpensive AA, C and D dry-cell batteries. The electrodes are zinc and carbon, with an acidic paste between them that serves as the electrolyte.
* Alkaline battery - Used in common Duracell and Energizer batteries, the electrodes are zinc and manganese-oxide, with an alkaline electrolyte.
* Lithium photo battery - Lithium, lithium-iodide and lead-iodide are used in cameras because of their ability to supply power surges.
* Lead-acid battery - Used in automobiles, the electrodes are made of lead and lead-oxide with a strong acidic electrolyte (rechargeable).
* Nickel-cadmium battery - The electrodes are nickel-hydroxide and cadmium, with potassium-hydroxide as the electrolyte (rechargeable).
* Nickel-metal hydride battery - This battery is rapidly replacing nickel-cadmium because it does not suffer from the memory effect that nickel-cadmiums do (rechargeable).
* Lithium-ion battery - With a very good power-to-weight ratio, this is often found in high-end laptop computers and cell phones (rechargeable).
* Zinc-air battery - This battery is lightweight and rechargeable.
* Zinc-mercury oxide battery - This is often used in hearing-aids.
* Silver-zinc battery - This is used in aeronautical applications because the power-to-weight ratio is good.
* Metal-chloride battery - This is used in electric vehicles.


Now, something simple. Ish.


This is an AC Inverter drive. A rough comparison can be made between this and a carburetor. This complex machine (notice the can of WD-40 to the side for size comparison) trumps the cost of the motor and is the most apparent object you’ll see when you lift the hood of an EV. This takes the DC power from the batteries and converts it into AC Three Phase energy required for the induction motor. It’s not quite the workhorse of the EV’s, but it certainly does a key part.

Now that you’ve picked out your engine, batteries, and AC Drive, you have to figure out how to power up your automobile. I’ve already written about hybrid regenerative technology. While regenerative braking certainly plays a part in EVs, it is not enough to recover enough energy to fill the batteries.

1)Off-the-grid, “Plug In” recharging. This is certainly the most economic way to charge your electric car up in this day and age. There are two ways to charge up your vehicle. The first is from any household plug, and can deliver 120 or 240 volts to the car. The advantage to this technique is convenience-anywhere you find an external plug, you can charge up (even your neighbor’s home or the gas station down the street). The Disadvantage is charging time. It takes 10-12 hours for a full charge from a 120 Volt outlet and 4-5 hours from a 240-volt outlet

The second option is a magna-volt system, introduced when major auto industries began rolling out electric cars. The system is directly connected to a 240 volt, 40-amp circuit. This technique can charge a car in as few as two hours.


Another disadvantage to this system is that it cannot be called a “truly” clean vehicle. The power to charge it up has come off the grid from, likely, coal plants. It is still much cleaner than, say, the energy it takes to pump, ship, refine, ship, and pump gasoline into your car, then burn it.
However, it is much cheaper cost-wise to charge your car than fill it up. Here in Maine, it costs about 7 cents per kilowatt-hour of electricity. Say my car runs on 13 kilowatt-hours of energy, it would cost just under a dollar for a whole fill up. Of course, the range of the vehicle is about 50 miles but tell me where else you can travel 50 miles for a buck?

2) Solar
Solar is a fickle technology. If you live in sunny California, then this won’t be a problem for charging your car up and driving about. Again, here in Maine (even though the other New Englanders stole it from us) we have a saying: Don’t like the weather? Wait a minute. Sunlight is unpredictable, and cannot be a reliable means to charge your car. Likely, you would still charge your automobile up via option #1.
Solar panels can and should be installed to give you those extra miles on a sunny day. Another barrier to their introduction is cost. Though the price may be coming down, it will still cost you in the realm of several thousand dollars to cover the roof of your EV.

3) Hydrogen/Fuel cell.
It has been said over and over again by people much smarter and eloquent than myself, but I am stating it over again for posterity: Hydrogen Fuel Cells do not equal free and clean energy. If anything, hydrogen fuel cells replace the batteries in your car. With the disclaimer out of the way, you could hypothetically set up a windmill or solar power generator and buy your own hydrogen production kit to fuel yourself up. Until that day, you will be purchasing hydrogen that, most likely, will come from coal, nuclear, hydroelectric, or otherwise polluting energy source. Instead of plugging in your batteries at night, you fill up on compressed hydrogen.
I like fuel cells, though, they’re fun to talk about, so here’s a very nice illustration from the government on how fuel cells work:


So, to recap, this thing can change the world.

The range of an electric vehicle is only 50 or so miles. So what? If you live in a city, how many miles do you drive to work and back? Any extra expense you pay at the dealership is quickly made up for by paying $7 a week in fuel costs, especially in today’s uncertain (related to yesterday’s and tomorrow’s) oil market.
The enviroment can also be cleaned up if these engines are used in conjunction with cleaner coal technology in the immediate future. There are several ways which coal can be burned with next to zero emmissions. Let alone self-generation through wind or solar, or even fusion power. The important thing is that, were every city car to be replaced with an electric motor, air quality would increase along with a decrease in traffic noise (EVs run nearly silently). That little motor really can change things.

It took a lot of brain busting to knock this project out, and I’ve certainly learned a lot while writing it. I hope it’s just as helpful to you (And somewhat correct

Work Cited (In no particular order)

[edit on 27-3-2006 by TheGoodDoctorFunk]

[edit on 27-3-2006 by TheGoodDoctorFunk]

posted on Mar, 28 2006 @ 01:23 AM
Wow, i'll have to take a moment or ten to read it, but A for effort

posted on Mar, 28 2006 @ 01:41 AM
one nite my brother and i spent in the local RSL. we were designing a centrifcal force engine that creates its own electricy and uses magnets to carry a rotor around.
we spent till the early hours of the morning discussing and drawing on beer coasters. we came to the conclusion the motor wouldn't create enough torque to actually be able to move anything much heavier then the motor itself.

We took our design to our dad, who is an engineer. He turned around and told us....."You've just reinvented the electric motor."

We were devastated. We had plans and ideas scrawled down on about 15 coasters. all wasted.

what a blurry nite.

posted on Mar, 28 2006 @ 01:42 AM
Nice job

posted on Mar, 28 2006 @ 01:55 AM
Another well researched and informative contribution from TheGoodDoctorFunk.

I particularly enjoyed your prior submission on combustion engines, just wanted to mention that.

Keep up the good work.

posted on Mar, 28 2006 @ 06:02 AM
i work with e-motors all day long ,a/c motors that we use are 80%efficient.
There will come a day that they will be 100%efficient,of course you need other equipment to make this happen,superdrives,microprossers,vmc20's(the brain)and a nice power supply(2000 lbs dc 48volt electric storage battery).

nice post

posted on Mar, 28 2006 @ 01:59 PM
Wow, timoothy, thank you very much. A compliment coming from someone who works with electric motors is the highest I could have hoped for. I have some more articles on the different aspects of energy use and production in the pipeline, but will have to wait untill I finish up my term papers. Thanks for the kind words, it really makes it worth it!

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