Rotating motion of a D.C motor

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Discussion Overview

The discussion revolves around the effects of the number of blades on the output current of a D.C. motor used as a dynamo in a turbine project. Participants explore the relationship between blade count and current generation, as well as seek methods for analyzing results and finding secondary sources for comparison.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant describes an experiment using a D.C. motor with varying numbers of blades and notes an increase in current output with more blades, but anticipates a drop in current beyond a certain point due to mass.
  • Another participant suggests that a mathematical model is necessary to relate current output to the number of blades, indicating that the relationship may be parabolic.
  • Some participants inquire about existing research or experiments related to the effect of blade count on current output, expressing a need for secondary sources to support their findings.
  • A participant mentions having plotted a graph of current output versus the number of blades and finding a parabolic relationship, indicating they have derived an equation from their data.
  • There is a suggestion to investigate Pelton Wheels as a relevant concept, though one participant expresses uncertainty about how to analyze their results without specific references.

Areas of Agreement / Disagreement

Participants generally agree on the need for a mathematical model and secondary sources for comparison, but there is no consensus on specific methodologies or the best way to analyze results. The discussion includes varying levels of familiarity with turbine theory and hydrodynamics.

Contextual Notes

Participants acknowledge the complexity of fluid dynamics and the specific conditions of their experiments, which may affect the applicability of general formulas or models.

Who May Find This Useful

Students and researchers interested in turbine design, D.C. motor applications, and the relationship between blade count and output in fluid dynamics may find this discussion relevant.

Advait
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I am doing this project to check how the number of baldes of a turbine affects its output. So I used a D.C motor which can be used as a dynamo. I attached a blade to it and forced water on to it and as a result of the rotation motion of the D.C motor/dynamo current was produced. Then I attached two blades to the motor and noticed that more current was produced. There will be a certain point after which there will be so many blades that their mass will be too much and hence the current would drop. Can anyone tell me how I can find the optimum number of baldes at which the "turbine" will give maximum output current?

Mass of one blade = 4.5 grams
Force of water (flow rate) = 50 ml per sec

And apart from that question above can someone tell me how i can analyse my results the best and draw up a good conclusion?
 
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Is there a formula I could use for any calculations?
 
There's no way to answer that in a general sense. There's too many things that are particular to your system.

Have you done any research on Pelton Wheels?
 
No What are they? What are too many things particular to my system. If that is the case then how can I analyse my results?
 
Atleast can anyone give me a link to results for experiments carried out by other people to see the effect of number of blades on the current output? That will help me get secondary research for my project.
 
Hi Advait,

you need a mathematical model of your system. This is not a trivial thing to do, because you have to write equations between your observables. For example, you know that the current output 'I' is related to the number of blades, 'N'.
If you plot a graph of I vs N ( I is the y, N is the x) you might be able to guess the equation between I and N. If your theory is correct, you should see a rising I, then a peak and then I falling.

You're in new territory here, just try and get as many data points as you can.
 
I already did that. And yes I do get a parabolic graph and I also calculated the equation for that graph using my GDC (TI-84). It seems to work. I mean I get an equation and from that I can find optimum number of blades with maximum output. Thanks.

And now I just need Secondary Sources to compare with my own results as a conclusion to my essay. Can anyone provide me links where someone has stated how many blades they use and what is their output or something like that. For example, tell me if there is any site which tells us the number of blades to the Niagara Dam and its output. Then using my graph and estimating the water flow rate I can theoretically calculate its output and check.
 
OK. The theory of turbines and water-wheels looks difficult, as are most things involving fluid flow. I did a google search with 'Turbine theory' and 'water-wheel theory and go a lot of hits.

I can't help further than that, not knowing much about hydrodynamics.
 
  • #10
Yes. I did. but now I just need secondary sources to back up my results. For example if anyone can provide a site where someone has already shown there results to varying number of blades then I could compare my results with his/her and make my project better.
 

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