Electric Generators

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Question:

If I have a motor that drives an alternator, is it possible to get more electricity out of the alternator than I put into the motor to turn the alternator?

For example:

I have a 12 volt DC motor with an approximate 3 to1 pully/belt/pully drive from the motor to the alternator. The alternator is a 12 volt DC alternator capable of producing 200 amps. Lets say the motor is using 10 amps at 12 volts DC. Can I get more than 10 amps at 12 volts DC out of the alternator?

Do you know how to change an alternator with a built-in voltage regulator from producing 12 volts DC to produce 17 volts DC?
 
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  • #2
berkeman
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Question:

If I have a motor that drives an alternator, is it possible to get more electricity out of the alternator than I put into the motor to turn the alternator?

For example:

I have a 12 volt DC motor with an approximate 3 to1 pully/belt/pully drive from the motor to the alternator. The alternator is a 12 volt DC alternator capable of producing 200 amps. Lets say the motor is using 10 amps at 12 volts DC. Can I get more than 10 amps at 12 volts DC out of the alternator?

Do you know how to change an alternator with a built-in voltage regulator from producing 12 volts DC to produce 17 volts DC?
You will always get less power out of the system than you put in. You can change the voltages, and you can change the currents, but the power out Po = Vo * Io will always be less than the power in Pi = Vi * Ii.
 
  • #3
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Even though the alternator is a High Output alternator?

It just seems to me that I could turn the alternator with the motor using a 3 to 1 ratio reduction so the alternator was spinning faster than the motor and the alternator being a High Output alternator would output more that was input into the motor.

Is there aanything I can do to make this happen?
 
  • #4
russ_watters
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Even though the alternator is a High Output alternator?

It just seems to me that I could turn the alternator with the motor using a 3 to 1 ratio reduction so the alternator was spinning faster than the motor and the alternator being a High Output alternator would output more that was input into the motor.

Is there aanything I can do to make this happen?
If it were possible, every engineer would already be doing it in their own home. But clearly, it is a violation of conservation of energy.

There are typically two errors that lead to this. First, power (rotational) is torque times rotation rate. Gears utilize mechanical advantage in the same way as levers and pulleys to increase force while decreasing distance (or vice versa) in proportion. Ie, a 2:1 gear ratio doubles the rpm while halving the torque, so 2*.5=1..... power hasn't changed.

The second error is not realizing that a generator actually requires an input of mechanical power. A generator isn't just an empty shaft that you spin, it's an electromagnetic device that resists your attempts to rotate it. The best generators generate almost as much electrical energy as mechanical energy required to spin them.
 
  • #5
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Finally, an answer that makes since.

I didn't realize that I was reducing the torque when I mounted a larger pully on the motor, trying, to turn the alternator faster. Nor that the torque should figure into the Power formula.

Humm.

I'll look at my problem from that angle and see what I need to change.

What I'm trying to do is using a motor-alternator setup to replace solar cells because of the lack of consistant sun light in Missouri. Wind power is also unreliable where I live.
 
  • #6
OmCheeto
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I built such a device last year.

pf_motor_generator.jpg


Though it's purpose was a bit different.

The last experiment was to determine how much power was being lost by the fan belt.
It turned out to be around 100 watts.

I decided that either direct drive, or a more flexible serpentine belt would be more efficient.
 
  • #7
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Thanks,

Here's what mine looks like:
 

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  • #8
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oneoleguy,

While I realize you probably did not read the forum rules, and I doubt seriously you would realize that your concept is in direct violation of them, I thought I would take the time to 1) Post the particular rule and 2) Explain briefly why the idea won't work.

The Rule:
Perpetual motion and "free energy" discussions
Search PF and you will find many threads that have been closed in a number of forums. As for S&D, any claim of this nature would be reproducible and/or testable by the scientific community; hence there is no need for debate.

Taken from: https://www.physicsforums.com/showthread.php?t=414380
Your idea is a variation on perpetual motion. That is, you want to get more energy out of a system than you put into it. This simply cannot happen. No combination of belts, gears, magnets, coils or wishes is going to make this happen. I am certain you think your idea is not about perpetual motion, but I assure you it is.

In the last 100 years mankind has made huge strides in making energy cheap and available, but with the average American consuming over 60kWh/Day most people think it should be "cheaper". 1kWh is roughly the equivalent to a 150lb person running ~6mph for 1 hour. So, in order to "do the work yourself" that you consume in fossil fuel and electricity each day, you would need to run ~6mph 60 hours a day. The point is, most people have no idea how much energy they consume, nor how cheap it really is. But most people think that there must be some short-cut to get their 60kWh/Day "cheaper", LOL.

Cheers,

Fish
 
  • #9
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This is a better picture of it:

[PLAIN]http://oneoleguy.com/images/Generator [Broken] Prototype.JPG[/PLAIN]
 
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  • #10
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Fish,

As you said: "I am certain you think your idea is not about perpetual motion, but I assure you it is."

Your assumption that I was not thinking in terms of perpetual motion is correct! However, I didn't know that what I'm attempting to do is a variation of it. I know that perpetual motion is not possible in this Universe, however, all I'm trying to do is generate electricity while avoiding the need for a large array of expensive batteries that are required in the Solar or Wind generators.

It seemed to me that I could turn an alternator that should be producing more energy than the motor took to turn the alternator. I didn't know that there was a mechanical energy component involved.

PS. I'm not interested in perpetual motion! In my mind, I didn't think I was talking about it, though I accept that you think I am. Howwver, with your permission, I would like to continue discussing this generator.

PPS. Here is what I'm trying to acheive! Using a motor-alternator to replace the Solar cells or Wind generator. I look at it this way, the alternator has had a lot of energy put into it by magnetizing the iron bars in it. By passing the resulting magnets by the coils of the alternator, I'm just trying to coax this energy out in the form of electricity.

PPSS. Is it possible that the process of magnetizing the iron bars in the alternator does not storing energy as I think? And perhaps that is the flaw in my intentions?
 
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  • #11
OmCheeto
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Here is what I'm trying to acheive! Using a motor-alternator to replace the Solar cells or Wind generator. I look at it this way, the alternator has had a lot of energy put into it by magnetizing the iron bars in it. By passing the resulting magnets by the coils of the alternator, I'm just trying to coax this energy out in the form of electricity.

PPSS. Is it possible that the process of magnetizing the iron objects does not storing energy as I think? And perhaps that is the flaw in my intentions?
What you are now describing seems to be a permanent magnet alternator, which somehow has it's "magnetic" energy extracted.

Even if this were possible, which I'm not saying isn't possible as I've never considered such a thing, the energy extracted would be greatly disappointing.

I would read Russ's mantra 100 times, and then think about it some more:

Russ said:
A generator isn't just an empty shaft that you spin, it's an electromagnetic device that resists your attempts to rotate it.
Russ said:
A generator isn't just an empty shaft that you spin, it's an electromagnetic device that resists your attempts to rotate it.
Russ said:
A generator isn't just an empty shaft that you spin, it's an electromagnetic device that resists your attempts to rotate it.
Russ said:
A generator isn't just an empty shaft that you spin, it's an electromagnetic device that resists your attempts to rotate it.
et cetera, et cetera, et cetera........

ps. What's the zero rpm torque at full voltage for your motor? I've been considering getting one.

pps. Is that an E-tek, Perm, or Mars motor? Looks like a Mars to me.
 
  • #12
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I've been thinking about the amount of energy I could get out of my alternator's magnets and I wonder: "If the magnetizer used to magnetize the iron bars is run for X number of minutes at y strength, then is the amount of energy imparted into the magnet large or small"? Aligned with your thinking, it's small. Now lets take into account the passage of this magnetized iron rod over a coil of wires in the alternator. What energy output then?

I thought it would be big because the alternator is rate at 200 amps. I bought a DC ammeter to find out what the output of the alternator is. I'm trying to install today and will let you know what the results are.

I don't know the torque of the motor, but it is really strong. What equipment would I use to test for the torque?


Hey, a question I can answer! I found it on eBay!

The motor is: 12 24 48 Volt DC Motor Etek MT/Pattern Permanent Magnet (search on this)

10 HP MOTOR and or 8000 WATT DC GENERATOR

Fits on most common Etek bolt patterns and mounts

Vertical Stator Design (Magnets on BOTH sides of the stator)

Worlds most powerful motor for its weight to hp ratio!

Over one hp per lb. / 28 horse power maximum - See details below


The next revolution in direct drive wind turbine technology!
LOTS OF LOW END POWER GENERATION ABILITY!
Fits on most common Etek bolt patterns and mounts
Permanent Magnet Motor /Generator
NO EXPENSIVE CONTROLLER REQUIRED
Let your battery voltage
be your speed controller.
Low speed 6 volts
Medium speed 12 volts.
High speed 24 volts
Hyper speed 48 volts
Just Plug & Play -
No expensive motor controller needed -
Brush technology is older but they are very
quick and simple to replace in the field AND
brushed motors convert more electricity into
usable horsepower! - 94% Electric Efficiency!
OR - GET A CONTROLLER -
http://www.sevcon.com/pages/millipak4Q.html
OR
http://www.4qd.co.uk/prod/4qd.html


--------------------------------------------------------------------------------

Specifications:
7.91" diameter / 5.64" length
7/8" shaft with 3/16" keyway by 1.75" long (threaded center)
Torque constant: 1.14 in-lb/Amp (0.13 Nm/Amp)
12V to 48V (has been run up to 96V / 45 sec. max. / 25 hp)
72 RPM per volt (3456rpm @ 48V / continuous duty)
Can be used as a generator, makes power when turned (Requires 120 amp blocking diode)
Great for VERY low voltages at high amp loads
Perfect for building simple, cheap and dependable low voltage wind turbines.
A put-up and forget design! Expect decades of dependable service life.
Rain, ice and weather proof electronics.
10 horsepower continuous duty at 48 volts.
Max motor currents: 330A for 2 minutes / 480A for 45 seconds.
10 horsepower max at 48 volts continuous duty!
14 horsepower max at 60 volts continuous duty with optional air cooling port.
Works for both CW or CCW rotations.
Epoxy/Lam rotor efficiency = 94% (Brushed motors convert more electricity into usable horsepower)
Weighs 22 lbs. / Dimensions - 8"X 9"X 9"
(From now, I enhanced the package, because one motor was broken in transit, so the weight now is 11.20KG/24.64Ibs)
 
  • #13
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1
Last try :-)

It seemed to me that I could turn an alternator that should be producing more energy than the motor took to turn the alternator.
If this is what you think, then why not take the next logical step and connect the output from your generator to your motor, thus powering your motor and the rest of your house with the generator?

This is the definition of perpetual motion, and it simply does not work. Absolutely best case you might turn 85% of the motor's output into electricity via the alternator. The motor, in turn, might turn 85% of the output of your alternator back into mechanical energy. In a very short period of time your system will be at rest.

If you decide to plug the motor into the grid, 85% of the power it uses will be turned into mechanical energy. If you connect that mechanical output to an alternator, it might turn 85% of that mechanical energy back into electricity. So best case you would get 72.25% of the energy out of the alternator that you consumed in your motor.

85% efficient motors and alternators are few and far between. More typical values are in the 25% to 65% range.

Fish
 
  • #14
russ_watters
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I didn't realize that I was reducing the torque when I mounted a larger pully on the motor, trying, to turn the alternator faster. Nor that the torque should figure into the Power formula.
Here's the wiki on gears:
For an ideal machine, the two equations can be combined, indicating that the force exerted IN to such a machine (denominator of first ratio) multiplied by the distance moved IN (numerator of second ratio) will equal the force exerted OUT of the machine multiplied by the distance moved OUT (i.e., work IN equals work OUT).
http://en.wikipedia.org/wiki/Mechanical_advantage

And the wiki on torque:
A conversion factor may be necessary when using different units of power, torque, or angular speed. For example, if rotational speed (revolutions per time) is used in place of angular speed (radians per time), we multiply by a factor of 2π radians per revolution.
http://en.wikipedia.org/wiki/Torque#Relationship_between_torque.2C_power_and_energy

You'll learn a lot by reading and understanding both.
What I'm trying to do is using a motor-alternator setup to replace solar cells because of the lack of consistant sun light in Missouri. Wind power is also unreliable where I live.
Are you still trying even after having it explained that it is impossible? Please read and learn what is in those wikis.
 
  • #15
russ_watters
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PPSS. Is it possible that the process of magnetizing the iron bars in the alternator does not storing energy as I think? And perhaps that is the flaw in my intentions?
The alternator doesn't recover energy stored in the magnets inside it. Even if it could, that would be a tiny fraction of the energy that an alternator actually generates.
 
  • #16
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O.k.

Perhaps I'm wrong.

I'd still like to figure out what I'm doing and what my results should be compared with what they are.

For instance:

I finally installed my ammeter and tested the setup this morning. The results are:

1) -12 amps with only the motor running
2) -30 amps with the motor and alternator running.

My initial thoughts were that the alternator should be putting out something, then the ammeter reading would be greater than a -12.

I've had the alternator checked out and it was working.

I connected 2 12 volt battreries in series to the motor and the alternator on it's own 12 volt battery "not in circuit" with the motor still puts out negative amps. I've checked the ammeter connections several times to ensure that I connected it correctly and the wires are "as shown" in the ammeters schematic. How does an alternator put out negative current?

This is the information that I have on the alternator:

FORD CARD AND TRUCK High OUTPUT
200 Plus Amp One-Wire Alternator

* Ford 3G conversion alternator w/v-belt & serpentine pulley (Large Case)
* 200 amp
* Internally regulated
* OEM hookup
* Excellent output at idle
* Dual internal fans
 
  • #17
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After several attempts, I finally got the motor and alternator on seperate batteries. The alternator is putting out -3.4 amps. I had the alternator checked two places. 1) at a parts house which said it was bad and 2) at an alternator shop which said it was good.

There are 2 wires going to the regulator from the alternator, what would happen if I reversed the wires? Blow it up of fix it?
 
  • #18
russ_watters
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How does an alternator put out negative current?
That's it's purpose! It drives current backwards through the battery to recharge it.
 
  • #19
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Dear Oneoleguy,
You can never produce more power from less power source. The alternator produces alternate energy. This term is used in vehicles where energy is produced by gasoline.
The gears are used to increase torque not power. The power after the gear is always less than the power before the gear. This is because the gears are also waste some powers in the form of friction and heat.
The other example is transformer. Let's suppose we have step up transformer, whose input is 220V while the output is 11000V. But don't confuse from this figure because power is the product of voltage and current, so if 100A current is flowing at input than input power becomes Pi=220x100=22000Watts. So in this case output power can not be greater than or even equal to 22000 Watts, means output current will remain less than 2A. This is because transformer also produce some heat as power loss.
 
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  • #20
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OmCheeto Thats OK understood that your not interested but now I need to reply to your short comment.
I understand that when you plug an electric drill into your generator the load is reflected to the output of the motor, Im not talking about a little 100 amp or 200 amp unit yet. It would not be practical but the application I am talking about is a larger design to replace coal, oil, gas and wind generator plants.
Should we give up because of what someone said, then there would be nothing!!! What I am offering is an oportunity for anyone that wants to go outside the box take a chance at making history and frankly a great deal of money to hear me out before some old fuddy duddy claiming to be an inventor who throws up their hands and gives a defeatest attitude to influence you.
The principal is the same but the resources are different from back when they first proved that power to tourque was not a viable way to produce electricity, that should not be the case now!!!
Anyone interested in looking at this contact me!
 
  • #21
jim hardy
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lots of peoiple think that because a generator (alternator) is so easy to spin by hand when it's not connected to anything,

that it is also easy to spin when it's making power,

and you can do what you describe.

in fact a generator (alternator) gets real hard to turn when it's making power.

that's why your automobile's fanbelt is so tight. If it's loose, the belt will slip and the generator (alternator) will slow down and not make even enough electricity to keep up with your headlights, let alone the airconditioner. I have fixed several mysterious "my battery was dead this morning" troubles by tightening up a loose fanbelt.

That's why the 400 ton alternator in your electric company's generating plant is driven by a thousand ton steam turbine and not an electric motor.
That 400 ton alternator is electrically identical to the one in your automobile - three phase wye. It's just bigger, about fifty feet long with a 3 foot diameter shaft and the wires in it are a foot thick.
old jim
 
  • #22
jim hardy
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i hope you're not paying them.

suggested reading :

Isaac Asimov's "The Gods Themselves"
fictional story of a similar undertaking but with good explanation of the basic physics required.

old jim
 
  • #23
OmCheeto
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I also have many things running around in my head. One idea, which I'm quite sure will work, is worth quite a bit.

But I have never asked anyone, here or outside the forum, for money to implement the idea.
 
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  • #24
OmCheeto
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i hope you're not paying them.

suggested reading :

Isaac Asimov's "The Gods Themselves"
fictional story of a similar undertaking but with good explanation of the basic physics required.

old jim

God! I hope they don't delete this post. That was one of my favorite books. And the surrounding omitted phrases, are one of my favorite quotes.
 
  • #25
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Whenever such an idea is rebuked, the answer is "but if all inventor hopefuls listened to the deniers, nothing would move forward". Well that statement taken in a vacuum is true. But this theory has been put forth since the beginning of time.

In 1976, I was an EE major, undergrad. In the study room, an ME major was discussing electric car theories with me & others. Here was his brilliant suggestion. When the batteries drive the motor to move the car, attach a belt to said motor & turn an alternator. As the batteries provide energy to turn the motor, the alternator restores some energy back to the battery.

I tried to tell him that "but Mike, if you did that ---", I was cut off before I could begin. He said "Claude, I know what you're thinking. There is no way to get perpetual motion. I know that! But with my way, instead of 3 hour battery life, we get 4 to 5. There are losses, it won't go forever, but it will improve".

I said, "No, no, no. Instead of 3 hrs. batt life, we'll get 2.9 hrs. Every joule into the alternator came from the battery. Every joule into the motor came from the battery. Along the way, the alternator drive belt loses joules in friction, as well as the copper windings heating up. You cannot gain anything at all. Not only does it not go forever, not only does it not go longer, it goes a little shorter in battery life with the alternator attached." He was convinced that I'm crazy, & today, he probably still thinks so.

I may be crazy & wrong on other questions, but he was wrong that day. A generator is also a motor & vice versa. When current is present in the generator winding torque is produced due to the magnetic field surrounding the wire in windings. As luck would have it, this torque is always in the "wrong direction". It works against you. It acts like a motor opposing you.

Previous posters correctly stated this counter torque issue. Nobody is trying to discourage innovation, but this horse has been beyond beaten to death. The poor thing has disintegrated.

Finding & employing natural gas, wind power, solar power, geothermal, nuclear fusion (big research to do that), & new forms are the answer. This motor/generator thing comes up every week & has been proven impossible since day one. Be curious, inquisitive, bold, but don't be naive, or defiant of Mother Nature. Defying Mother Nature results in egg on the defiers face, not on hers.

Claude
 
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