Author Topic: Anybody guess what this is going to be???  (Read 17608 times)

Offline Rustkolector

  • Full Member
  • ****
  • Posts: 79
Re: Anybody guess what this is going to be???
« Reply #60 on: July 13, 2013, 04:08:14 PM »
Chuck,
Depending on the magnets and air gap you use, cogging can be excessive. I made a alternator from an 18 pole ceiling fan motor. Anxious to test it's output, I stuck the magnets on my iron rotor and inserted it into the stator. Actually, the rotor was pulled from my hand into the stator ruining a couple of the neo magnets. I couldn't turn it nor could I remove it by hand due to the magnetic force. I was able to  minimize the cogging effect by angling the rotor magnets on the rotor so that one magnetic pole on the rotor spanned two stator poles. Cogging was still present but acceptable, however I still needed a plastic sleeve around the rotor magnets to protect them from damage as rotor insertion is still tricky. Using an 18 pole stator made it fairly easy for me to angle my magnets. Fewer poles makes angling between two stator poles more difficult. I suggest you try to use as many poles as you can fit into to stator.  A 4" stator will make this difficult. Mine was 6" dia. The other benefit of added poles is voltage at lower RPM. I am not sure a non magnetic rotor would be of any benefit, but it might have some relative to cogging, but not to electrical output.

Jeff

Offline Bezalel

  • Full Member
  • ****
  • Posts: 376
  • - Skype:Bezalel2000
Re: Anybody guess what this is going to be???
« Reply #61 on: July 13, 2013, 04:18:14 PM »
Hi Chuck
 
Great to hear the green LEDs worked out nice and bright.  :whoohoo:
 
Are you aiming for some filament lumins loomens lemings light bulbs to load up the alternator when you beef it up some more?
 
The circuit with 18 Green LEDs sounds like you calculated that out to be just right for using the alternator windings as your LED current limiter.
 
If you don't mind me stealing your thunder Chuck, I'll explain (for those interested) how you would have arrived at that magic number 18.
 
A typical forward Bias voltage for green LEDs is about 2.2V - the internal impedance of the alternator was measured at 22 ohm (IIRC) therefore out of the 4V measured at the alternator output (unloaded), 1.8V (=4v-2.2v) must be across the internal impedance of the windings when LED load is applied.
1.8V over 22 ohm will pass 80mA.
That should give about 9mA through each of the 9 conducting LEDs during each half wave of the AC cycle (close to the typical 10mA required)
 
Setting the circuit up this way there is no need for the usual current limiting resistor.  Neat trick Chuck  :praise2: 
 
I'm looking forward to seeing your next mods   :ThumbsUp: :ThumbsUp:
 
Cheers
 
Bez
 
 
 
Queensland - wet one day, humid the next

Offline cfellows

  • Full Member
  • ****
  • Posts: 1700
Re: Anybody guess what this is going to be???
« Reply #62 on: July 15, 2013, 05:27:44 AM »
Thanks, Bez.  Actually I started with 6 LED's, the went to 12, and finally 18, all that I had.  I suspect it would have driven more.  However, I'm also hoping to run the engine at about 600 or 700 RPM, not the 1500 that my cordless drill provided.

I started work on a steel core stator.  I'm using a 1 1/8" long piece of 4" OD, 3.5" ID steel pipe as the outer ring. 





The coils are wound on HDPE plastic spools that started out 1" x 7/8" x 1/2" thick.  The center part of the spool is 3/8" diameter with a 1/4" hole through the center and winding space is about 1/4" x 1/4" or a little less since the windings don't go all the way out.  There are a total of about 260 turns of #28 copper wire per coil which is about 25% more than my other stator.







I profiled the inner radius of the coil form using a fly cutter on my mill/drill to cut the concave curve with the coil form held vertically on the outside edge of the vice jaws.  I formed the outer radius by mounting the coil form on the end of a 1/4" diameter expanding mandrel, then clamping the mandrel in the round tool bit hole on one of my boring bars and swinging the outside of the coil form at the proper diameter in my lathe.  Each coil form will have a 1/4" diameter x .4" long steel  rod with a very thin, 5/16" diameter flat head on the inner end and a 6-32 threaded hole in the other end.  Recessed, 6-32 socket head cap screws from the outside will screw into the outer end of the rod and secure the coil forms to the stator ring.

Don't have any idea how much cogging will be an issure or what kind of power I will get out of this thing or if my engine will even turn it.  It's all a learning experience at this point.

Chuck
So many projects, so little time...

Offline Don1966

  • Full Member
  • *****
  • Posts: 5993
  • Morgan City, LA (Along the Gulf Coast)
Re: Anybody guess what this is going to be???
« Reply #63 on: July 15, 2013, 05:45:48 AM »
Chuck why are you using a steel stator? You should have no cogging because there are no steel pole pieces. The steel stator is only good if the pole pieces are steel to help distribute the magnetic lines of force. Sorry bud but this will not help much. The steel ring will increase eddy current losses.
Your orginal design should product more output then you have. Did you pass a compass inside the stator to check that the poles were north and south on every other poles. Just use a battery to power the stator with to do this. Do it just to double check they are correct.

Don
« Last Edit: July 15, 2013, 06:04:09 AM by Don1966 »

Offline cfellows

  • Full Member
  • ****
  • Posts: 1700
Re: Anybody guess what this is going to be???
« Reply #64 on: July 15, 2013, 03:39:38 PM »
Chuck why are you using a steel stator? You should have no cogging because there are no steel pole pieces. The steel stator is only good if the pole pieces are steel to help distribute the magnetic lines of force. Sorry bud but this will not help much. The steel ring will increase eddy current losses.
Your orginal design should product more output then you have. Did you pass a compass inside the stator to check that the poles were north and south on every other poles. Just use a battery to power the stator with to do this. Do it just to double check they are correct.

Don

There will be a 1/4" diameter steel core in the coil that holds the coil to the steel ring.
So many projects, so little time...

Offline Bezalel

  • Full Member
  • ****
  • Posts: 376
  • - Skype:Bezalel2000
Re: Anybody guess what this is going to be???
« Reply #65 on: July 16, 2013, 01:07:17 PM »
Thanks, Bez.  Actually I started with 6 LED's, the went to 12, and finally 18, all that I had.  I suspect it would have driven more.  However, I'm also hoping to run the engine at about 600 or 700 RPM, not the 1500 that my cordless drill provided.


Probably a good thing you didn't start with less than 6 LEDs -  the estimated 80mA is shared between the 3 forward biased diodes, 26 mA is pushing towards the limits. They tend to fritz out between 20-30mA.
 
Bez
Queensland - wet one day, humid the next