Author Topic: test coil  (Read 5953 times)

0 Members and 1 Guest are viewing this topic.

Jason Wilkinson

  • Full Member
  • ***
  • Posts: 181
  • Country: bb
test coil
« on: April 26, 2010, 09:36:49 AM »
Hi to all , the new board is quite  challenge to navigate around >:(
i've read the advice about doing a test coil first but am not sure how to go about this,as 2 methods come to mind. 1) make coil to fit into available space in stator or 2)make coil to determine number of windings fot cutin. I assume the second method require both rotor disc completed and assembled  with the required air gap. As i see it one would have to guess at a number of windings far from required  and then keep reducing  eg make coil 50 turns, place in air gap spin, measure,eh eh too many , reduce to 45 and repeat , ending up with a length of wire 5 wraps long.  That's how i'm thinking . Please put me right
 Thanks    Jason

ghurd

  • Super Hero Member Plus
  • *******
  • Posts: 8059
Re: test coil
« Reply #1 on: April 26, 2010, 10:41:44 AM »
Sounds right to me.
I thought a test coil was only to determine the number of turns required.
Will need the 2nd rotor on and adjusted to something realistic.

The test coil is only to get voltage for calculations, so can use small gauge wire.
G-

(PS- I moved it to something more appropriate.  Took me a while to figure the new board out too)
www.ghurd.info<<<-----Information on my Controller

ChrisOlson

  • SuperHero Member
  • ******
  • Posts: 3642
  • Country: us
Re: test coil
« Reply #2 on: April 26, 2010, 11:07:35 AM »
As i see it one would have to guess at a number of windings far from required  and then keep reducing  eg make coil 50 turns, place in air gap spin, measure,eh eh too many , reduce to 45 and repeat , ending up with a length of wire 5 wraps long.  That's how i'm thinking . Please put me right

You do the test coil to determine the proper number of turns for cut-in.  You have to have the mag rotors assembled with the correct air gap, stick the coil in there and spin it at the rpm that the rotor is supposed to cut in at.  You can guess on the number of turns and go from there.  The voltage you get from the test coil is proportional to the number of turns in it - for example, if you wind 50 turns and get 5 volts, if you reduce it to 30 turns you'll get 3 volts, or if you increase it to 60 turns you'll get 6 volts.  So you only need to do one test.

Once you find out what the test coil makes you multiply that voltage times the number of coils in one phase, then if it's star configuration you multiply that by 1.732.  This will be the open AC voltage of the generator in star.  Then you multiply that by 1.4 to get the DC voltage that you'll get out of the rectifiers.

So here's an example with a 12 pole 9 coil 24 volt:
To get full charging system voltage you'll need 20 AC volts at cut-in = 28 / 1.4
The voltage per phase, in star, would be 11.55 = 20 / 1.732
The voltage per coil would be 3.85 = 11.55 / 3

Then, whatever number of turns you come up with, I usually throw in one more turn to compensate for voltage drop across the rectifier.  That should get you right in the ballpark.

It's important to note that full charging voltage on a 12 volt is 14 volts, 24 is 28 volts, and 48 is 56 volts.  If you wind for full charging voltage and you hammer the batteries down to 12, 24 or 48 respectively, the turbine will run in stall at cut-in trying to bring the batteries back up.  It's not as big of a deal with 12 volt as it is for 48.  So if you're building a 48 you might want to use the low end (48-50 volts) as the cut-in DC voltage so you don't end up with turbines like I got that are overwound and stall badly unless the batteries are fully charged.
--
Chris

Jason Wilkinson

  • Full Member
  • ***
  • Posts: 181
  • Country: bb
Re: test coil
« Reply #3 on: April 27, 2010, 11:55:39 AM »
Thanks guys,i was more thinking about the physical dimension of the coil
 Jason

awk

  • Newbie
  • *
  • Posts: 36
Re: test coil
« Reply #4 on: July 21, 2010, 12:34:35 PM »
hi
i have 1.18inch dia 5mm neo magnets.
i want to make a dual rotor system 12 mag on each plates.9 coil on stator.
what gauge of wire and how many turns do i use to get charging voltage in 10mph wind speed.

jimovonz

  • Sr. Member
  • ****
  • Posts: 339
Re: test coil
« Reply #5 on: July 21, 2010, 04:16:50 PM »
Awk, you just posted this exact same question in a new story when this thread already explains the procedure for finding your answer. To make it absolutely clear - you need to complete your magnetic assembly and make a single test coil (roughly the same dimensions as the finished coils using any gauge you please) Then you can calculate the number of turns required to achieve your desired cutin and estimate what size wire you can fit in (use the largest that will fit). It is all covered here many times over. If you are sincere in your intention to make a wind turbine then I would suggest that you have a lot more reading to do...