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Asking about AC, Transformers, and Generating Electricity

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Dracet
#1
Aug16-08, 02:29 PM
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Well this is my first post on this topic so my questions might be relatively simple compared to most. First thing I would like to ask is Is it possible to connect to different AC power generators together to power one object? If I'm not using the right terminology let me know.
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Redbelly98
#2
Aug16-08, 03:22 PM
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Yes, it's possible to connect more than one AC generator together to power a single object.

Disclaimer:
It's also possible to hurt or kill yourself and other people by connecting more than one AC generator together.
Dracet
#3
Aug18-08, 08:52 AM
P: 5
Thank you for the disclaimer I guess people have tried before. Do you happen to know of a safe way to do it? I'm playing with very low amounts of voltage. Just using a card board box wrapped in copper wire with a magnet rotating inside it. So I'm not creating much but I wanted to see if I could combine two of them to create a little more power instead of Making a bigger cardboard box. Oh I'm just powering a low voltage lightbulb.

berkeman
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Aug18-08, 11:40 AM
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Asking about AC, Transformers, and Generating Electricity

Combining power sources is non-trivial. The AC Mains power grid is an example of coordinated power sources being combined (gas-fired power plants, hydroelectric dam generators, etc.), and to be honest, I don't know how they pull it off. I do know that generators like dam turbines need to be brought close to the phase of the grid before being connected into it (or else bad things happen to the generator!).

You will need a way to coordinate the phase of the two generators (like have them share a common rotor shaft...), and you will need a way to ensure that they both have about the same output voltage....
Dracet
#5
Aug18-08, 01:38 PM
P: 5
wow that was more complicated than I thought it would be. So tell me if I'm wrong but if I take the copper wire and split it so that there is a coil on one side of the cardboard box and a coil on the other that it may work? And that they both should have about the same output voltage before I have the two connect to supply one object with energy from both? Did I get that about right? Let me know please. Oh and what is the AC mains power grid? I've been searching through the different videos that show how a generator works. I didn't hear anything about that. If it's a business trade secret or something nevermind lol
chroot
#6
Aug18-08, 01:44 PM
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You'll never be able to accomplish the feats berkeman mentioned with a tabletop wire-coil generator turned by hand. In those circumstances, it is effectively impossible to combine the two generators' outputs in any useful way.

- Warren
isly ilwott
#7
Aug18-08, 03:12 PM
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Quote Quote by chroot View Post
You'll never be able to accomplish the feats berkeman mentioned with a tabletop wire-coil generator turned by hand. In those circumstances, it is effectively impossible to combine the two generators' outputs in any useful way.

- Warren
Perhaps if they were driven by a common shaft, constructed near identically, phased properly and fitted with impedance matching resistors it would work.

It is highly unlikely (in my humble opinion) that a novice generator constructor would be able to match impedances enough to preclude the need of adjustment in one winding or the other. However, the feat he describes is not impossible. It's called parallel generation...and it happens all the time. For big generators, the paralleling gear is sophisticated and costly. For lab experiments utilizing hand-turned generators in the 2-10 watt range, it'll be hard to hurt anyone with fault currents.
berkeman
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Aug18-08, 04:14 PM
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Quote Quote by Dracet View Post
Oh and what is the AC mains power grid?
That's the term for the grid of high-power transmission wires that deliver electricity to your home from the generation plants. Multiple generation plants, multiple connections in the grid for redundancy, and multiple distribution stations for stepping the voltage up and then back down, for distriburion over long transmission lines. Amazing stuff.

http://en.wikipedia.org/wiki/Distributed_generation
berkeman
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Aug18-08, 05:08 PM
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Quote Quote by berkeman View Post
That's the term for the grid of high-power transmission wires that deliver electricity to your home from the generation plants. Multiple generation plants, multiple connections in the grid for redundancy, and multiple distribution stations for stepping the voltage up and then back down, for distriburion over long transmission lines. Amazing stuff.

http://en.wikipedia.org/wiki/Distributed_generation
Actually, that URL is more for co-generation of electricity on a small scale -- my error. This is a better article on the AC Mains Power Distribution Grid:

http://www.howstuffworks.com/power.htm


.
Redbelly98
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Aug18-08, 05:49 PM
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Quote Quote by Dracet View Post
... I wanted to see if I could combine two of them to create a little more power instead of Making a bigger cardboard box....
The solution to this is rather simple. Just wrap twice as much wire around a single box.
chayced
#11
Aug18-08, 06:55 PM
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Quote Quote by chroot View Post
You'll never be able to accomplish the feats berkeman mentioned with a tabletop wire-coil generator turned by hand. In those circumstances, it is effectively impossible to combine the two generators' outputs in any useful way.

- Warren
By my thinking, you can directly couple two AC machines with no problems so long as neither of them is turning when you couple them. They will naturally seek being in phase with one another, so much so that driving one faster than the other will turn one into a motor and the other into a generator.

The problem with paralleling AC machines is that you have to get the voltages to match, get the frequency to match and get the phase to match. If you don't have any of the three then starting them both should be fine, so long as they are not held out of phase by gears or a common shaft.

That is NOT a recomendation to do this though. Out of phase machines can cause nasty voltage swings and destruction mayhem. Oh and smoke too.
berkeman
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Aug18-08, 06:59 PM
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Semi-related and interesting factoid. If you watch all the windmills (of a particular design) in a hillside windmill farm, if they are adding power to the grid, they are all turning at the same rate with their blades in-phase. If they are off-grid, they can be turning at random speeds and phases....
Dracet
#13
Aug18-08, 07:15 PM
P: 5
So in other words I cannot generate more power by just connecting to generators together because in the end it will put out the same amount? Like if I have three generators running off same size gears all turning at the same speed in the end I would still have the same amount of power if I was just using one generator?
berkeman
#14
Aug18-08, 07:20 PM
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Quote Quote by Dracet View Post
So in other words I cannot generate more power by just connecting to generators together because in the end it will put out the same amount?
That's not at all what we are saying, and the AC Mains Power Grid is an example that it can be done. It's just not a simple thing to do. You could potentially use chayced's idea of spinning up one generator and having its output power the other as a motor until you get up near operating speed, and then clutch in the power source for the 2nd generator. Or you could work out a control circuit for the 2nd generator, so that it actively matches the speed and phase of the 1st generator before you connect them in parallel electrically (that's how hydroelectric dam generators are put on-grid.... very carefully).
Dracet
#15
Aug18-08, 07:39 PM
P: 5
I see. So if I needed something done like that I would need someone who know what they were doing. Now I may be wrong by while I was looking it seemed to me that positive and negative were relative terms. Positive meaning power coming in and negative being power used and sent back to where positive began. I thought of this when I saw a diagram of a simple transformer (it was just an iron piece). It was because of that the wires wrapped around it was connected and the ends of the wire were connected to the bulbs screws. One on the negative and one on the positive. So it seems that all in all electricity has to be in a sustained loop. Not just sent to an object and used never to return. I don't know if that makes any sense but does it sound right?
Redbelly98
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Aug18-08, 08:45 PM
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Yes, for electric current to flow there must be a loop in the circuit. That's why electrical power cords have two wires and 2 prongs.

Since you're just trying to power a low-voltage light bulb, those responding in this thread can best help by suggesting different ways to increase the power, in case you can't get enough from a single generator of the type you described.

Synchronizing two such generators is possible, but as others have said it's difficult to do in practice.

Wrapping more wire around one generator box, as I suggested earlier.

Or, adding a second magnet to one generator box. Assuming you can fit another one in.

Spinning the magnet(s) faster would also be a way to generate more power.

Edit:
It occurs to me that if the magnets in two different generators were attached to a single, long shaft, they would be synchronized.
Redbelly98
#17
Aug19-08, 07:26 AM
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Quote Quote by berkeman View Post
You will need a way to coordinate the phase of the two generators (like have them share a common rotor shaft...), and you will need a way to ensure that they both have about the same output voltage....
Giving credit where it's due: berkeman thought of having magnets on a common shaft first!


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