Science Buddies: "Ask an Expert"

I am planning to make a magnetic generator & i have a question :

If i provide a disk with 12 numbers of neodymium (1x1”x1”cylinder) (n48) magnets around it , moving by motor clock wise at 1500 rpm ,
( magnet specification: Br: 13.80- 14.20 KG, Hcb: > = 10.5 Koe, Hcj: > = 11 KOe )

The magnets facing 12 Coils , each coil (3”x 2”) with 782 winding turns (copper awg 15),
Each coil inductance = 8.685 mH & each coil resistance = 1.051 ohms .

Following discription :

A- 12 coils at stator (on circle shape) facing 12 magnets at one side of the round rotor.
B- each coil cylindrical 3”x 2”.
C- between coil to coil 1.1”.
D- Coils with 6mm hall in the middle of the 3” round side.
E- 12 magnets are distributed along the circle of the rotor (round disk).
F- each magnet 1”roud face would be facing exactly the middle of the 3” round face coil .
G- radius of the magnets from the axis of the rotor = 8”
H- radius of the coils from the axis of the stator = 8”

So how many volts can be gain from the output of the coils ?

You are off into an area where it is more "art" than "science". Companies that manufacture generators ususally develop some proprietary computer modeling programs that are based on their past designs and provide some approximations that are resonably good over a very limited range; however, even those programs won't adequately predict results when parameters are changed beyond where their models break down.

To help you understand this better, if you modeled something that only had 3 coils and 3 magnets, the mutual induction between the coils and the magnetic field interactions between magnets would be much simpler. Even in that case, how you connect the coils and how carefully you control the gaps and how uniform the coil dimensions and orientations are can cause some phase differences that affect the end result.

Even the load you use to test the generator with will affect the results.

Try reading up on multi-phase AC circuits to get some additional background on phase angles and RMS voltage and current and wave shapes and an introduction to analyzing some simpler circuits before you jump into a 12 phase design.

If your intention is to make a DC generator, you didn't provide any information on the commutator. Alternatively, you might think about an alternator circuit with rectifiers similar to what is used in automobiles as these are easier to analyze, design, and test than DC generators.

In any case, you aren't going to produce a constant voltage out of any magnetic induction generator.

Craig_Bridge wrote:You are off into an area where it is more "art" than "science". Companies that manufacture generators ususally develop some proprietary computer modeling programs that are based on their past designs and provide some approximations that are resonably good over a very limited range; however, even those programs won't adequately predict results when parameters are changed beyond where their models break down.

To help you understand this better, if you modeled something that only had 3 coils and 3 magnets, the mutual induction between the coils and the magnetic field interactions between magnets would be much simpler. Even in that case, how you connect the coils and how carefully you control the gaps and how uniform the coil dimensions and orientations are can cause some phase differences that affect the end result.

Even the load you use to test the generator with will affect the results.

Try reading up on multi-phase AC circuits to get some additional background on phase angles and RMS voltage and current and wave shapes and an introduction to analyzing some simpler circuits before you jump into a 12 phase design.

If your intention is to make a DC generator, you didn't provide any information on the commutator. Alternatively, you might think about an alternator circuit with rectifiers similar to what is used in automobiles as these are easier to analyze, design, and test than DC generators.

In any case, you aren't going to produce a constant voltage out of any magnetic induction generator.

Hi,
Im sorry I don't understand how their question would be more art than science? Wouldn't it be more physics than art? Im asking this because I have the same exact question but I was looking for a formula or formulae, for figuring this out. It would be great appreciated if you could respond when convenient but there is no need to worry rushing my question. I am quite fascinated with the theory of the N Machine and if it were true wouldn't the Laws of Physics need to be rewritten? Thank you for your time. Have a wonderful morning, afternoon, day, evening which ever comes fist.

The laws of physics as we understand them do not have to be violated for us to ignore some factor assuming it is not relavant to sufficiently model the behavior of something and end up with the wrong prediction.

The "ART" involved in this case is an appreciation for what is and isn't important in creating a sufficiently accurate model to adequately predict the result without making it overly complex to the point that a mathmatical solution to the model is impossible to achieve in a reasonable amount of time.

The fundamental problem is that current flowing in your coils will induce a magnetic field and other magnetic fields will induce a current. The coils are not single points in space so the field strength will vary in time and space. Additionally, the geometry is not static, you have rotation. Your permanent magnets are not single points, and their magnetic fields will not produce a uniform symetric pattern in the presence of other magnetic fields. Current can also be induced in the magnets themselves further altering their magnetic fields dynamically in time.

Any metal structure used to hold mechanical allignments will alter the magnetic fields and will have current flowing in them as well. Structures may not be sufficiently rigid and can vibrate and alter the geometries. Some motors and generators are mounted on rubber dampers to allow for this which can allow rotation under dynamic load changes.

Many companies have come up with their own proprietary models that apply to their specific design approaches. I know of no general purpose model that you can plug in any arbitrary designs in. Engineers in these companies have spent many many years at refining their models and typically have at least BSEE degrees and many of the larger companies have many masters and doctorate degrees among their engineering staff. Each time they get a result where their model does not predict the result, they figure out why and refine their model to improve its accuracy so that they can produce a more efficient product and spend less time in trial and error in new product development.

If you want to attempt to model a generator yourself, you should simplify your design down to one or two coils and one or two magnets. Build one and experiment with it and see how close your model comes to predicting the behavior before you attempt to tackle something more complex. Experiment with cores. Experiment with laminating the cores. Figure out how to measure magnetic field strength. Figure out how to investigate phase angles for voltage and current. Figure out how to analyze the efficiency of your design.

In other words, investigate for yourself what works and what doesn't work and figure out why.