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Best magnet size to coil size ratio for an electromagnetic generator?

what is the best magnet (neodymium - disk shape) size to copper coil size ratio for optimal electron production per one break/pass of flux lines across coil at a 1/2" distance? For instance, if magnet is 2" diameter what is best inner diameter for copper coil? Best number of windings? Best gauge wire? what are the best specs for optimal electron production before you reach "over kill". I know some things are variable like core material and magnet grade. I'm looking for an all things being equal kind of scenario. Also what would be the best thickness of magnet at 2" diameter? If anyone could point me in the direction of any existing tables or ratio information on this subject it would be appreciated. Thank you.

lars.b1 month ago

Here is an excerpt from http://www.free-energy-info.com/Chapt2.html

"First and foremost, high performance can only be achieved with the clever use of power collection coils. These coils need to be positioned accurately and their power collection restricted to just a very short arc of operation by connecting them to, and disconnecting them from, the output circuit at just the right instant so that the back EMF generated when the current draw stops, actually contributes to the drive of the rotor, speeding it on it's way and raising the overall efficiency of the motor/generator as a whole.


Next, the shape of the magnets used is important as the length to width proportion of the magnet alters the pattern of it's magnetic fields. In direct opposition to the diagram shown above, the magnets need to be much longer than their width (or in the case of cylindrical magnets, much longer than their diameter).

Further, a good deal of experimentation has shown that the size and shape of the electromagnets and pick-up coils has a major influence on the performance. The cross-sectional area of the core of the pick-up coils should be four times that of the cross-sectional area of the permanent magnets in the rotor. The reverse is true for the cores of the drive coils as their cores should have a cross-sectional area of just one quarter of the rotor magnet cross-sectional area.

[...]

Now for some practical details. It is suggested that a good length for the power pick-up coils can be determined by using the “paper clip test”. This is done by taking one of the permanent magnets used in the rotor, and measuring the distance at which that magnet just begins to lift one end of a 32 mm (1.25 inch) paper clip off the table. The optimum length of each coil from end to end is exactly the same as the distance at which the paper clip starts to lift.



The core material used in the electromagnets can be of various different types including advanced materials and alloys such as ‘Somalloy’ or 'Metglas'. The power pick-up coil proportions are important as an electromagnet becomes less and less effective as its length increases, and eventually, the part furthest from the active end can actually be a hindrance to the effective operation. A good coil shape is one which you would not expect, with the coil width being, perhaps 50% greater than the coil length[...]"

coil-to-mag-ratio.gif
lars.b1 month ago

Here is an excerpt from http://www.free-energy-info.com/Chapt2.html

"Now for some practical details. It is suggested that a good length for the power pick-up coils can be determined by using the “paper clip test”. This is done by taking one of the permanent magnets used in the rotor, and measuring the distance at which that magnet just begins to lift one end of a 32 mm (1.25 inch) paper clip off the table. The optimum length of each coil from end to end is exactly the same as the distance at which the paper clip starts to lift.


The core material used in the electromagnets can be of various different types including advanced materials and alloys such as ‘Somalloy’ or 'Metglas'. The power pick-up coil proportions are important as an electromagnet becomes less and less effective as its length increases, and eventually, the part furthest from the active end can actually be a hindrance to the effective operation. A good coil shape is one which you would not expect, with the coil width being, perhaps 50% greater than the coil length[...]"

cblomquist1 year ago
Great e-book resource for many zero-point energy projects. I am not the author, but it's got some really intriguing info and research.

http://www.free-energy-info.tuks.nl

There are those who have generated many kW using relatively small setups. Yes that's KILOwatts!
jetboy4 years ago
i am using 2x1x1/2 inch bar magnets and need to know the best size coil for my wind turbine, the gauge is 14 and am using 35 turns of two parralel strands to produce 12 volts
Hi Jetboy, the rule of thumb when building a generator is what ever size magets you use, that should be the inside diameter of your coil. The magnet should be able to barely squeeze through the inside diameter of the coil!
Jewson2 years ago
If your lazy you could get a dc motor and turn it manually and it will produce electricity. You could take it apart see what kind of wire and magnets are used and learn from it.
I'm looking at the neo lab magnets that are threaded so I can mount an array of them to a fixed surface. for the coils, I have found some of the surface mount IC design charging coils that handle quite a bit of amperage. with rectification and voltage regulation, would this be a way to get it done ???

coils here http://www.coilcraft.com/pfl.cfm
I am working on a project still on paper. I'm experimenting with charging a small Li-On battery and a supercap via inductance. Here's the jest of it, and I'm just wondering what type of magnets and coils I might need. I would need the smallest coils available that could still produce a few volts at low current applications.

I want to be able to make a generator for low voltage (3.5V DC or less) @ around 500-800mA

I want the magnets in a fixed position, and the coils (several of them) would be in motion continuously.

Induce this current into the coils to a Li-On charging circuit and/or a super cap for power storage.

ANY advice would be much appreciated, and I would share my results.
Ed Nature4 years ago
I'm a teacher looking to do extra-curricular electromagnetic experiments with his students. These are the same questions I have. I seriously doubt that these experiments have yet to be completed - probably 50 or more years ago. So where do I go to read and study? Don't have the time to conduct these exploratory experiments as this is not my primary job or responsibility - those of which suck up most of my waking hours each day. I and reader #1 are looking for simple guidance as to where we can find these answers. If graphs aren't available - just some rule of thumb stuff to get us going. The only answer I saw given was that the magnet should be as close as possible to the wire coil. Isn't there somewhere a set of graphs plotting variables such as size of magnet, strength of magnet, gauge wire, rotational speed of magnet, vibrational period of magnet, etc. - all giving amount of electrical output? Thus, for a classroom teacher - who can recommend the best size neodymium magnet with the right size magnet wire and number of loops and specs how to build the device, to be used in harvesting the kinetic energy of a moving river - or the wind outside (Beaufort scale up to 4) via a simple student built turbine?
Oh and also, you should look into the difference between SYNCHRONOUS and ASYNCHRONOUS and other induction generators.

In essence its all just waving magnets past each other.
Ed, I would advise starting with the simple 'nails and wrapped wire' motor experiment. Then, disconnect the power and hook the home brew genny up to a resistor and a multimeter, or a bulb.

If you are teaching secondary school I would say that wire guages, rot speeds etc are arbitrary. If what you make works then that is good enough. I would advise AGAINST using anything other than a standard lab magnet as anything with a stronger flux can easily lead to SERIOUS INJURY due to the currents that you can produce. Unless you are planning to power your lab, I'd say that any power produced would be a result.

What i will tell you is that it is the MASS of the MAGNET or ROTOR that in fact produces the biggest change in output. More turns of wire is better and the guage of wire is designers choice. Basically you choose a guage depending on how much current you expect to be producing. You can find this max current info on farnell datasheets. There is nothing wrong with getting a heavier guage than you expect, to be on the safe side. Aaaand it must be laminated. Just don't use thin wire or you'll start a fire.

There is no real rule of thumb when it comes to designing a genny; but the reason you can't find any info is because any change to any part of a motor/gen produces a change in the 'equivalent circuit' of that motor/gen and the results may not be as you'd expect.

The maths of a motor may look hairy but when you've learned it once you can apply it to most motors. Depending on the type of machine you are making, the number of "Poles" is important. If you want an idea of what you'll get out of it before you make it, the maths is really the only way. Otherwise its pretty much guesswork. This is your homework.

Start with a small weak magnet, make a prototype then you can use a more powerful magnet of the same dimensions once you have evaluated the safety aspect - WHICH IS OF THE UTMOST IMPORTANCE WHEN PRODUCING POWER.

Sorry for a late reply :)
haskinsmp3 years ago
I was looking into this as well. The best I ever got in explaining this is an Excel file I found somewhere. Perhaps with a little knowledge this can explain things for some and for others at least help.
I was looking at the document...what does the F mean?

Thanks
I am no Electronics Engineer, but I would say it was capacitance or F for Farads. If you look up Farad on Wikipedia it will help to solve the formula given (I/2rm).
brokengun5 years ago
These questions are not really specific enough. There is no "best wire size", etc. Basically it all depends on what you want to achieve, what voltage, what kind of power you are looking at producing, and what RPM the generator will be spinning at. All of these things need to be taken into account. I can't find specific places that will give you this info. I have seen it for a few various wind turbine designs but I do not have the raw equations to calculate your own alternator specifications. Really a lot of it is just trial and error. There is a lot of theory and science behind it all but in the end there are a lot of variables to consider. For example magnet strength and air gap. Not to mention the physical limitations of the materials. In general I will say that as a rule of thumb for axial flux permanent magnet generators, the hole in the middle of the coil is roughly the size of the magnet. You should be able to squeeze the magnet through the center of the coil. That seems to hold true at most all sizes of axial flux machines. Lots more to learn about alternator/generator design and theory. My suggestion: read, study, ask questions.
Try this link http://www.6pie.com/faradayslaw.php
kchaitanya3 years ago
can anybody help me in finding the size of the magnets to produce 240v in generator... i am planning to use neodymium magnets ... please this is my mail id .. krishnachaitanya.maruvada@gmail.com
cdcobre4 years ago
I am searching for the same answers for a different wind generator I am tryng to create.
brokengun is 100 % right I am going  nuts with so much you have to put together.
Faraday laws in is a good way to start knowing about this topic.
this guy in youtube give me a great info just wear something to help with the bad audio on the videos an learn, it is fun after all.

how to wind copper coils tightly for wind turbine stators part 1 and 2

Sorry if I made any mistakes my language is Spanish.