Author Topic: Windings, wire diameter & RPMs = volts & amps  (Read 1510 times)

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force9BOAT

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Windings, wire diameter & RPMs = volts & amps
« on: November 06, 2005, 01:12:00 AM »
Hello,


I have some more basic questions



  1. Does increasing the number of windings increase voltage, amps or both?  My guess is voltage.
  2. Does increasing wire diameter increase voltage, amps or both?  My guess is current (amps).
  3. Does increasing alternator RPMs increase voltage, amps or both?  My guess is both.


Are my guesses correct?


Basically, I'm trying to understand what is better, more windings with thinner wire or less windings with thicker wire for a given desired output voltage.


Thank you,

Rob

« Last Edit: November 06, 2005, 01:12:00 AM by (unknown) »

terry5732

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Re: Windings, wire diameter & RPMs
« Reply #1 on: November 05, 2005, 09:15:27 PM »


  1. Increasing number of windings increases voltage only.
  2. Increasing wire size increases internal heating only.
  3. Increasing RPM increases voltage only.


« Last Edit: November 05, 2005, 09:15:27 PM by terry5732 »

willib

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Re: Windings, wire diameter
« Reply #2 on: November 05, 2005, 11:29:20 PM »


  1. ) say that you had one turn per coil (just an example) increasing that to 50 turns will increase both voltage and current..
  2. for the same dimension coil , increasing the wire dia. , will decrease the voltage ,and the current , because the number of turns is less, but the coil resistance will also be less , which is a good thing..
  3. say your gen is running at 100 rpm , increasing the RPM to 200 increases both the voltage and current..


imho

« Last Edit: November 05, 2005, 11:29:20 PM by willib »
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Flux

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Re: Windings, wire diameter & RPMs
« Reply #3 on: November 05, 2005, 11:51:05 PM »
Sorry life is not that simple. The things are interrelated and don't act on their own.


The direct effect of increasing turns is to increase voltage off load (EMF) . When there is a circuit and current is flowing then anything can happen depending on the conditions.


Increasing the wire size reduces the resistance, which gives you the ability to produce more amps for the same amount of losses ( heat in the stator)


If there is a circuit and there is current flowing then increase in speed will increase the current. If the load is other than a battery then volts should rise as well, but if the load is a battery with dump control then the volts may be held constant.


I know that this doesn't help you but it is better to try and understand rather than work from a series of assumptions.


I assume you are thinking about battery charging and what really happens is this.


For a given set of magnets you need sufficient turns to reach battery volts ( rectified output) at a chosen cut in speed, the lowest speed at which you get current.


The winding space will dictate what thickness of wire you can get in with the chosen number of turns. Then the resistance of the winding will decide how many amps you get at each speed.


If the current is less than you want you either go for more magnets or increase the cut in speed and try again.


Bear in mind that that this also needs to be linked to the type and size of the prop so that it can produce the chosen speeds with the wind available.


If you are new to this, base your experiments on something that works until you gain enough experience to be able to predict what effect changes make.


Flux

« Last Edit: November 05, 2005, 11:51:05 PM by Flux »

tecker

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Re: Windings, wire diameter & RPMs =
« Reply #4 on: November 06, 2005, 01:56:36 AM »
he fact that all of the factors are related is most definitely true .A discussion of

coil construction is mute until you establish what type of magnetic field you can construct .This will dictate the the amount of induction and so the coil can take shape voltage, and the current you can achieve will be a function of the field you have . You have a window of coil construction with a given size  size and speed of operation .    
« Last Edit: November 06, 2005, 01:56:36 AM by tecker »

finnsawyer

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Re: Windings, wire diameter & RPMs
« Reply #5 on: November 06, 2005, 07:42:33 AM »
Good job.  You saved me the trouble of wading in here.  I would like to point out that in the real world going from a single turn to say fifty turns doesn't necessarily mean a fifty times increase in voltage, as the coil needs length and width and because of this not all of the flux will pass through all of the turns.  This is due to the tendency of the magnetic field to spread out as it passes through the air above a magnet.  So some flux leaks away before it reaches the top turns.  The moral here is to study and understand the implication of Faraday's law.
« Last Edit: November 06, 2005, 07:42:33 AM by finnsawyer »

picmacmillan

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coil size
« Reply #6 on: November 06, 2005, 02:35:56 PM »
thought i would add 2 cents more here...one other factor that is very important to potential power output is the thickness of the stator(when all coils are finished),, regardless of turns..you will want the stator to be thin enough so you get optimum useage of your magnets, and thick enough so it doesnt warp....too thick a stator is something that most new folks try to achieve( i did this myself), by trying to increase the number of turns in the wire we make the stator too thick and thus reducing the magnets ability to do their job...and as stated above, we have too much resistance in the coils reducing our output significantly...for instance i had used # 18 wire, 200 turns and this produced 1 ohm of resistance per coil..in a 12 volt application the bigger coils turned out to be too thick for the magnets i had purchased to produce a strong field, and the resistance in the coils all but took away most of the power the genny could have produced....good learning curve when you wast money like i did to try and improve on someones idea, but not doing the research and ask questions...you are on the right track already, by asking the questions....something you should be proud of, it will save you alot of time, money and anguish later...good luck on your project....pickster
« Last Edit: November 06, 2005, 02:35:56 PM by picmacmillan »

terry5732

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Re: Windings, wire diameter
« Reply #7 on: November 06, 2005, 06:34:11 PM »
Number of turns DOESN'T increase current. It  increases voltage only. If you have increased voltage and same amperage you have increased watts. Current=amps! not watts! If you have wire thicker than you really need you will have eddy current drag and waste heat not more amps. The only way to just increase amps is to have a stronger magnet. No amount or size of wire changes your amperage.
« Last Edit: November 06, 2005, 06:34:11 PM by terry5732 »

force9BOAT

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Re: Windings, wire diameter & RPMs
« Reply #8 on: November 06, 2005, 07:45:43 PM »
I would like to thank the many people who stepped up to answer my questions.  I understand much better now.  I have just one more question.  What is meant my "cut-in" speed?  Is that the RPM where the voltage reaches the level needed to charge a given battery?  


Thank you,

Rob

« Last Edit: November 06, 2005, 07:45:43 PM by force9BOAT »

TomW

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Re: Windings, wire diameter & RPMs
« Reply #9 on: November 06, 2005, 08:01:33 PM »
force9;


BINGO


Cheers.


TomW

« Last Edit: November 06, 2005, 08:01:33 PM by TomW »
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