Generator Power vs Magnetic Field Power: What's the Difference?

[rfstanton]

In my experience, seems you can't get something for nothing (or little) but was just curious. What is the difference in conventional generator power and power generated simply by passing a conductor through a stationary magnetic field.

 

[OmCheeto]

In my experience, seems you can't get something for nothing (or little) but was just curious. What is the difference in conventional generator power and power generated simply by passing a conductor through a stationary magnetic field.

There is no difference.

 

[rfstanton]

If less resistance is required if the magnetic fields do not interact why don't conventional generators use this setup?

 

[OmCheeto]

If less resistance is required if the magnetic fields do not interact why don't conventional generators use this setup?

Conventional often implies that it is cheaper to do it that way.

 

[rfstanton]

Conventional often implies that it is cheaper to do it that way.

How can it be cheaper to generate electricity when more resistance is encountered with conventional setups? Maybe has something to do with size and/or magnetic density?

 

[uart]

How can it be cheaper to generate electricity when more resistance is encountered with conventional setups? Maybe has something to do with size and/or magnetic density?

Because it's not true. You just made that up and have presented no evidence as to why it's true. You are working under a false assumption.

 

[OmCheeto]

How can it be cheaper to generate electricity when more resistance is encountered with conventional setups? Maybe has something to do with size and/or magnetic density?

I do not understand your question.

Are you submitting your questions through a language translator? The syntax of your questions seem to not conform to the standards of the English language as I have been taught.

Where are you from?

hmmm... Are you a friend of the Devil's Avacado?

Who are you?

Who are you? You are clearly at the wrong place. Please read the https://www.physicsforums.com/showthread.php?t=5374", or return to Maharaji.net.

 

[Bob S]

In my experience, seems you can't get something for nothing (or little) but was just curious. What is the difference in conventional generator power and power generated simply by passing a conductor through a stationary magnetic field.

Review the theory of homopolar generators. See
http://en.wikipedia.org/wiki/Homopolar_generator
Look in particular at the photograph of the flywheel in the 500 MJ homopolar generator (color) picture, which rotated in a stationary magnetic field. This generator ran successfully for a few years at the Australian National University. Thie difference is that the homopolar generator works on the Lorentz force principle, while conventional generators run on the Faraday Induction Law principle. See also
http://www.animations.physics.unsw.edu.au/jw/homopolar.htm
Bob S

 

[rfstanton]

I do not understand your question.

Are you submitting your questions through a language translator? The syntax of your questions seem to not conform to the standards of the English language as I have been taught.

Where are you from?

hmmm... Are you a friend of the Devil's Avacado?

Evidently, I'm not a friend of DA, but I will rework my original question to see if I can make myself clearer. If I'm not mistaken, when conventional generators are turned faster, more resistance is encountered due to the design that creates interaction in the internal magnetic fields. In the other design I was referring to, two or more pairs of magnets are placed in close proximity and conductors are then passed through the gap between the magnets, thus creating a current. Also, as I understand el gen theory, the more conductors that pass per given unit of time, the more current is generated. Since the magnets in this case are stationary in reference to each and the conductors are not magnetic there should not be and increase in resistance in reference to an increase in the speed of the passing conductors. Sorry for the misunderstanding. RS

 

[keith03]

Take a look at Faradays Law. You are referring to an Axial Flux design. Two rotors of magnets rotating around a stator of coils. The answer is yes. The problem lies in generating the power to spin it. The real question is what amount is "usefull"? Home made axial flux designs are CAPAPABLE of 1000W. That is at MAX RPM. The entire principle of electricity generation involves moving magnets around a coil or vice versa. It IS how electricity is produced. Nuclear, Coal, Hydro, wind. All are forms of creating the power to move one of the objects around the other. What resistance are you referring to? Internal reisitance of the wire? Resistance of rotation? Also keeping the magnets stationary in this design creates more work, and also adds losses due to commutators.

 

[rfstanton]

Review the theory of homopolar generators. See
http://en.wikipedia.org/wiki/Homopolar_generator
Look in particular at the photograph of the flywheel in the 500 MJ homopolar generator (color) picture, which rotated in a stationary magnetic field. This generator ran successfully for a few years at the Australian National University. Thie difference is that the homopolar generator works on the Lorentz force principle, while conventional generators run on the Faraday Induction Law principle. See also
http://www.animations.physics.unsw.edu.au/jw/homopolar.htm
Bob S

Thanks, You got it! RS

 

[rfstanton]

Take a look at Faradays Law. You are referring to an Axial Flux design. Two rotors of magnets rotating around a stator of coils. The answer is yes. The problem lies in generating the power to spin it. The real question is what amount is "usefull"? Home made axial flux designs are CAPAPABLE of 1000W. That is at MAX RPM. The entire principle of electricity generation involves moving magnets around a coil or vice versa. It IS how electricity is produced. Nuclear, Coal, Hydro, wind. All are forms of creating the power to move one of the objects around the other. What resistance are you referring to? Internal reisitance of the wire? Resistance of rotation? Also keeping the magnets stationary in this design creates more work, and also adds losses due to commutators.

Your question about what resistance, in conventional generators and alternators, there is a design inherent that creates more resistance to turning with increase in speed due to interaction of internal magnet fields which increase the power output. With the other design I refer to, seems the only limitation to power output would be structural design limitations and size limitations. Bearing friction, air flow restricion, etc. should be minimal.

 

[uart]

With the other design I refer to, seems the only limitation to power output would be structural design limitations and size limitations. Bearing friction, air flow restricion, etc. should be minimal.

Complete nonsense.

If I'm not mistaken

Yeah I think that's the aspect of the discussion that you should really be concentrating on right now.

 

[keith03]

Its not complete nonsense. With the design in question, low RPM is used. Yes, The generated current does create its own field around the wire, and when a magnet approaches that is of opposite polarity, it does encounter resistance. This unfortunately is the draw back to power generation. This is about all I know about this aspect. Check out some graphs of generator output vs RPM. Most will rise, level out, and then degrate. The degration I believe is due to this. (amongst other things)

 

[Bob S]

This is about all I know about this aspect. Check out some graphs of generator output vs RPM. Most will rise, level out, and then degrate. The degration I believe is due to this. (amongst other things)

This sounds like the engine in my car; the horsepower rises to about 5500 RPM, then "degrates". Have you ever heard of back emf?
Bob S

 

[keith03]

My background is Electrical Engineering. I am uncertain if these two things are related, but I am assuming that the mechnical forces at work in an engine play a much larger role as to reversing the direction of a piston at high rpm. Interesting to see if the "stregnth" of the fields in the axial flux can compare linearly to the degration of the engine HP??

 

[vk6kro]

Can you generate useful power with just stationary magnets and moving wire conductor?

My local power station has been moving wires through a stationary magnetic field for as long as I can remember. It works just as well as moving a magnetic field past a stationary wire.
Both methods generate a voltage across the wire.

If people turn on their big-screen TVs then the generator gets harder to turn so they have to provide more power by pressing the accellerator pedal on the driving engine a little more. This uses more diesel, so the extra power comes at a price.

As you say, you can't get something for nothing. Whichever way you generate power, as soon as the current starts to flow, you have to supply mechanical power to get electrical power out and also to overcome friction losses etc in the generating equipment.

 

[rfstanton]

My background is Electrical Engineering. I am uncertain if these two things are related, but I am assuming that the mechnical forces at work in an engine play a much larger role as to reversing the direction of a piston at high rpm. Interesting to see if the "stregnth" of the fields in the axial flux can compare linearly to the degration of the engine HP??

Thanks guys for the helpful info. Follow up questions:Do you know any significant factors that would adversely affect grid tie in with the homopolar design?Advantages/disadvantages of a dc compared to ac homopolar design. As far as the other question at hand, having done a lot of mechanical work on engines, I believe the power curve in int. comb. engines has to do with inherent limitations of the fuel delivery sys. and the configuration of the intake, combustion chamber, exhaust, airflow through the system, each design favoring peak, etc. at different points. Electrical I imagine is basically the same in that each design has different inherent limitations in the various components. Please continue. I am still interested in persuing the differences in the "back pressures" encountered by a generator when more load is applied. Would this be the same in homopolar V conventional? I realize that homopolar design is not front and center in current study, so if it's too much research for the time you have, I understand. It's not life and death that I figure this out.
Referring back to a prior response, the picture is getting clearer, I didn't know about the field created around a conductor so that explains a lot esp. resistance to load. ...RS

 

[Bob S]

Homopolar generators are for very high current (meg-amp) unipolar pulses .They cannot generate ac power (50 Hz, 60 Hz). I don't know how the current could be regulated. Normal generators (alternators etc.) have feedback loops. I have heard that homopolar generators are dangerous to use; someone was blinded while using liquid sodium jets to make low-resistance electrical contact with the rim of the flywheel.
Bob S

 

[rfstanton]

Homopolar generators are for very high current (meg-amp) unipolar pulses .They cannot generate ac power (50 Hz, 60 Hz). I don't know how the current could be regulated. Normal generators (alternators etc.) have feedback loops. I have heard that homopolar generators are dangerous to use; someone was blinded while using liquid sodium jets to make low-resistance electrical contact with the rim of the flywheel.
Bob S

Bob,
Thanks for the concern, you're a real sweetheart. Don't worry I'm not gay. Not that I have anything against them. "To each it's own, it's all unknown, if dogs run free"...Bob Dylan. Anyway, I had the same thoughts regarding the homopolar design in that if the current generated was not being bled off somehow, I could see how a large charge could be built up and would eventually find ground (equilibrium). I thought that the homopolar design might have potential in low tech home grown power generation, but the more I find out about it, the more it seem prudent to let the more high tech folks pursue this technology. Looks like Parker Kinetic Design is hard at work on something to do with it. Unfortunately, it seems their line of research has to do with war machinery. My original line of thought was to find something that second,third, or maybe even first world could use to generate inexpensive, low tech elect. power. Maybe even using man or beast of burden as source of input power.
Pipe dream probably, but sometimes the diamonds get left lying in the sand. Thanks again.

...RS