How many turns to produce power on a spinning coil

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Discussion Overview

The discussion revolves around calculating the number of turns required for a coil to generate approximately 10V at 5W while spinning in a magnetic field. Participants explore the implications of coil size, magnetic field strength, and rotational speed on power generation, focusing on generator calculations rather than motor design.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks formulas to determine the number of turns needed for a coil to produce 10V at 5W in a specific magnetic field and rotational speed.
  • Another participant suggests using motor design calculators, but the original poster clarifies the need for generator calculations specifically.
  • A participant points out the importance of considering the resistance of the coil and potential voltage loss in the calculations.
  • Concerns are raised about the orientation of the coil in the magnetic field and how it affects performance, with a request for the best configuration to maximize power generation.
  • A ballpark calculation by one participant suggests that the required number of turns may be impractically high, indicating that the magnetic field strength might be insufficient for the desired output.
  • Another participant shares their experience with a portable generator design, noting a rough estimate of 1 turn per volt based on their rotor's specifications.

Areas of Agreement / Disagreement

Participants express varying views on the feasibility of generating the desired voltage and power with the specified parameters. There is no consensus on the optimal coil design or the effectiveness of the magnetic field strength, and the discussion remains unresolved regarding the best approach to achieve the goal.

Contextual Notes

Participants mention limitations related to the assumptions made in calculations, such as the coil's movement through the magnetic field and the potential voltage drop due to resistance. The discussion highlights the complexity of the problem without reaching definitive conclusions.

Who May Find This Useful

This discussion may be of interest to individuals working on generator design, those exploring electromagnetic principles, or anyone involved in practical applications of physics related to power generation.

Donglin
Does anyone have formulae to calculate the number of turns required on a coil to produce 10V at approx 5W.
I wish to have a coil spinning on a 16" diameter former in a 0.25 gauss magnetic field at a minimum of 2.2Hz. I need to be able to work out the size of coil and number of turns to produce approx 5W at 10-15V which will be DC rectified (frequency is not important).
The former is provided with a mechanical rotational force of between 2.2 - 16.6Hz. The magnetic field will vary between 0.25 - 0.65 gauss, but will be constant and parallel across the 16" former.
 
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Google "motor design calculator". There are many of them.

:welcome:
 
Thanks Anorlunda. I tried that but it gave me loads of motor calculators and I need generator calculations.
See attached. A coil on a rotating former in a low magnetic field. How small can I make the coil but still generate 10V at 5W approx.
 

Attachments

  • Coil Generator.png
    Coil Generator.png
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Perhaps see...
http://www.6pie.com/faradayslaw.php

One thing to watch out for is the resistance of the coil. You may need to correct for the voltage loss.

I should add that that web page isn't great but should give the basic idea.
 
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Hi CWatters,
That is great. I have looked at this, the issue I find with all these types of data is the way the coil moves in the magnetic field.
The diagrams show a coil as a single loop where one side is moving from N to S while the other side is moving from S to N of the magnetic field.
In my case, the coil is moving in it's entirety through the N to S field before then moving through the S to N field.
Without experimenting, what is the best orientation of the coil to get the best performance? What is the smallest size I can make the coil without losing the power required (although this is small).
 
I did a ball park calculation using the equation from the above link. I assumed the voltage required was 20V, the coil diameter was 0.1m (4") and it rotates at 2Hz (120rpm). I got a huge and impractical figure of 5 million turns. Due to the way your coil moves this would be an under estimate. Sorry but I think the mag field is way too weak to do what you want.
 
Thank you. I will have to rethink the strategy.
Was the equation you used N=-1*(-V/Δ((tesla*area meters squared)/seconds))?
 
Yes
 
I been working on portable generator for the last couple of months and this is what I came up with
The rotor has about 100 turns to produce 110vac so it's close to 1 turn per volt
I'm still working on it so I hope I am right
Hope I'm right
Tady
 

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