Page 1 of 1

Size & Shape of Coils

PostPosted: Wed May 19, 2010 4:47 pm
by pro-sound
Hi, newbie here, I've been toying around with stator sizes - I have made stators with specs given and it have worked. I understand that coils are wound up at a specific inner circumference and shape during my research, and all seem to have a similar size coils, which makes the stator core fairly huge.
I would like to know if there is any other way of winding the stator coils to make the inner circumference smaller, But without loosing voltage, current etc.
In otherwords, if I use 1mm enamel wire to wind up a coil with a Xmm inner circumference to get a the voltage & current that I require, will the same length of wire used in the first coil, wound to make another coil, but with a smaller inner circumference give me the same results.



Re: Size & Shape of Coils

PostPosted: Thu May 20, 2010 5:52 pm
by windgat
Hi Fabio. So you want a smaller stator? One way is to go for radial flux, where the magnets face outwards along the radius. Catch is this is not as easy to make, which is why mosy homemade option use the 'pancake' design. If you use stronger magets, you will make up for smaller coils.

Perhaps if you explain why you want a smaller stator, it would be easier to make some specific suggestions.

Re: Size & Shape of Coils

PostPosted: Sat Jun 12, 2010 12:28 am
by Boerseun459
Hi to everyone

I am the new kid on the block here and you will probably hear questions that are "old stuff", to most of you, by now.
So I have read the main page, about the stator, the rotors ect. I noticed that generally most of you stick to the concept of 12 magnets per rotor, 9 coils, 3 coils per phase. But I am an over-cautious fellow that hates to redo things and will therefor "overkill" most of the time. :lol: So I was thinking more in line of 16 magnets (50 x 25 x 12.5; N42 grade) per rotor and 12 coils; 4 coils per phase. I hope to achieve open circuit volts of 40 or higher. Can you please advise on the following:
1) the number of winds per coil and the thickness of the wire
2) the pros and cons if the coils are longer in length than the magnets (I was thinking of giving the coils a "tear drop" shape towards the centre hole of the stator)
3) if there is a rule when it comes to spacing between magnets on the same rotor

I appreciate any help I can get


Re: Size & Shape of Coils

PostPosted: Mon Jun 14, 2010 11:33 am
by windgat
Welcome! I use 1mm wire, and have seen over 20amps from a 3-phase stator. I have been tempted to use 1.2mm. Its mainly about how much can you fit in.
A teardrop sounds right - thats like a wedge shape, which is what I use. The more turns per coil, the higher the voltage at a given RPM. There is no point in having the up/down 'legs' of the coils longer than the magnets.

Spacing: Its crucial that the phases are 'in phase', in other words all the coils in one phase are passing over the same part of a magnet, of the same pole, at the same time. If you post a diagram of what you plan I can check if its ok. On the other hand, why not go with what others have found to work?

Re: Size & Shape of Coils

PostPosted: Tue Jun 15, 2010 2:09 pm
by Boerseun459
Hi Windgat

Thank you for the help so far,but I think my 3rd question was unclear; what I meant to ask was if there is a rule about the distance that the magnets must be apart from each other on the steel disk. From the photos it looks like the magnets are almost one magnet width apart at the closest point. With this in mind, I went and cut 16 "magnets" out of cardboard, 50 x 25, and arrange them in a circle. I ended up with a "rotor" that was 350mm in diameter. I gather that the stator must have the same diameter, so I went and drew a 350mm circle on cardboard and devided it into 12 wedges. I ended up with wedges that was 90mm wide at the top, 115mm long and 30mm at the bottom (I kept the "hole" for the rotor bolts in mind).

This typing is time consuming; have you ever used SKYPE? I have a webcam and a mic and would much rather give you a video call to explain things?

OK, so you said that the legs of the coils don`t need to be that long. So I was thinking of making the inside circumference of the coil smaller (see the modifications I made to one of your pics). That should leave plenty of space to try the 1.2mm wire?
If you look at my second photo, you will notice that only the "coils" marked with an A is 100% alligned with same poles facing upwards, but then all the sets of coils will get that chance as the rotors turn. Is that what you meant with "in phase"?


Re: Size & Shape of Coils

PostPosted: Sun Jun 20, 2010 11:39 pm
by windgat
Thats looking good! And, yes, your design looks like it will be in phase. A few points:
- Typing is consuming, yes, but that means others can benefit, and I repeat myself less often
- The coils will be thicker than your yellow line.
So the center of the coil legs is what you design to be in phase.
Take this thickness into account, to ensure you can fit the coils in the available space
- Its also important how you connect the coils of course. Every third one, to give 4 coils per phase looks right.

Re: Size & Shape of Coils

PostPosted: Sat Jul 10, 2010 3:53 pm
by Boerseun459
Thanx Windgat for the input.
Since I understand very little about electricity my following question might sound strange to you.
Hypothetically speaking, I have two windturbines and they are identical as far as all the components, number of coils and magnets are concerned, except for the one`s coils consists of 50 turns of 1.0mm wire and the other`s coils consists of 50 turns of 1.2mm wire (The inside circumference obviously smaller to make everything fit).

My question is what difference in preformance can be expected if both turbines are exposed to the same km/h wind?

Re: Size & Shape of Coils

PostPosted: Sun Jul 11, 2010 8:19 pm
by windgat
The thicker wire will have slightly less resistance, so will produce more power when heavy current is involved. But probably only slightly more.

The larger wire means a less optimal shape of the coils, so probably slightly less power in lower winds.

The main difference is that the thicker wire will be able to handle more current. I have seen over 20amps coming from a 1.0mm wire stator, so this will only be a factor for high currents.

Re: Size & Shape of Coils

PostPosted: Mon Jul 12, 2010 9:44 pm
by easyas
Hi Windgat

Just a question on coil shape, I have built a vertical wind generator, 9 coils with just one 12 magnetic plate.
On design, I did not worry about the inner dimmension of the coil. I used 40mm top and 20mm bottom for the inside of the coils. Why I am only using one magnetic plate is that I am not sure that the magnetic that I bought are the correct.

The maganetic are not rare earth magnets but have a grade of N36, size 46x20x10 mm

The results so far: 7 volts @ 25.5 mAmps.

Question should I expect more, coils 85T of 1mm, weight of coil 118grams, +- 16.3 meters.

Re: Size & Shape of Coils

PostPosted: Tue Jul 13, 2010 8:16 am
by windgat
You give volts and amps - what load have you connected which is taking that current? And what RPM was it? At first glance it seems very low. There is a thread somewhere in this forum on building a simple magnet strength measurer - I wonder if those magnets are really N36? Or if that is the same grading that is used for rare earths.

Are you rectifying? And have you connected up all three phases? If so, how?

Re: Size & Shape of Coils

PostPosted: Tue Jul 13, 2010 8:27 pm
by easyas
The nine coils are star connected in a three phase configuration. The RPM will be checked tomorrow as I am
getting a bicycle computer to do the job. The magents, yes I wonder too, the place where I bought the magnets
said they were N36.
The results are low and dishartining. What my next step is to measure the RPM and then to test each leg of the
rotor, as I have access to the star point.

Once I have these results I will post them and we can chat.

Re: Size & Shape of Coils

PostPosted: Wed Jul 14, 2010 9:05 pm
by easyas
Hi Windgat

Here are the results from tonights test. The speed recorded was 45 Kmh and the radius of the speed pickup is 120mm.
Doing the maths I get 198 rpm. The OC voltage 8.5 volts and current drawn by a computer fan was 23.5 mAmps.

Remember the magnets are not rare earth and I have only one set of 12 magents on 9 coils.
The resistance of each phase is 1.2 ohms.
The results thus far is not good.
I have a drawing that I did, can I mail it to you for checking, in pdf format.

What else can I look at ?

Re: Size & Shape of Coils

PostPosted: Wed Jul 14, 2010 11:43 pm
by windgat
Try and reconfigure your bicycle computer to read 19.8 km/h at that speed. Will save you some maths!

O.C. voltage 8.5V, and the fan wants what - 12V? They you would get a very low current. You need to match the test load to the voltage, so for e.g. you need to put a 6V fan on and see what current is drawn. Of course a fan is very low power. Maybe rather get a flat battery (6V is your case) and see how much current goes into that.

You should be able to post an attachment here - look for 'upload attachment' below your message box.

Re: Size & Shape of Coils

PostPosted: Thu Jul 15, 2010 7:59 pm
by easyas
Thanks, I have a look to see if the bicycle computer can be configured.
I do not have a 6volt battry but a flat 12 volt recharageable from my security system.
I'll hook it up and see what comes out.

Windgat, magnets, do you have access to rare earth magnets?. If so what grade and cost.
My current stator is 6mm plywood, the magnets are slotted into the plywood and skinned
with chopstrand and resin, total thickness, 12mm.

I am going to attempt to attach a pdf file which will show you the layout of my pancake in total

Re: Size & Shape of Coils

PostPosted: Fri Jul 16, 2010 12:34 am
by windgat
Layout looks good.

For my last course I got a set of 24 20x50x8mm N40 magnets for R1200 with a bulk order.

Stator... magnets... plywood?? Please explain. The magnets are normally on the rotor, and on steel plates...

Re: Size & Shape of Coils

PostPosted: Tue Jul 20, 2010 9:27 pm
by easyas
Hi Windgat

Attached plywood side view of my magnets.
Will be off the web for a while due to my car having
huge mechanical problems, cylinder head.

Once I sort the finance out then I chat to you about a set of good magnets.
Your magnets are they rare earth ?
cheers for now.

Re: Size & Shape of Coils

PostPosted: Wed Jul 28, 2010 7:50 pm
by easyas
Hi Windgat

No comment on the side view of the plywood rotor?
My car is back on the road and now my design computer is down, suspect a motherboard.
It never rains bu poors.


Re: Size & Shape of Coils

PostPosted: Sat Jul 31, 2010 9:30 pm
by windgat
Hello Mr Pie.

Interesting magnet mounting idea... Will you have coils on both sides of the magnets? I can't see that from the diagram. Usually the magnets are mounted on steel plates, which have the effect of directing the magnet flux to create a string field through the coils.

Yes, I only use rare earth magnets.

Re: Size & Shape of Coils

PostPosted: Mon Aug 02, 2010 8:27 pm
by easyas
Hi Windgat

Where did you get Mr Pie from ?
The construction is the same as yours, where two rotor magnetic plates with one set of 9 coils.
I see you did use a plywood construction with a steel plate, which collapesd due to magnetic force.
I get hold of the 5mm steel plat and see if I can get better results.

Just maybe that is my problem. I need to use steel plates to house my magents.
As soon as my fanancial status improves, I'll be chatting to you for a set magets.
As suspected had to buy a new computer as the motherboard crashed.

will keep intouch, thanks for the input thus far.
much appreciated.

Re: Size & Shape of Coils

PostPosted: Tue Aug 03, 2010 7:49 am
by windgat
Yes, you will get much more voltage per RPM by adding steel backing plates to the magnets.

Mr Pie? Well if your first name is 'easy as', ...

Re: Size & Shape of Coils

PostPosted: Tue Sep 07, 2010 9:01 pm
by easyas
Hi Windgat
Where can I get 5mm plates cut to size? I have spoken to on firm here in the northern sub's and they want to charge R158.00 per plate.
I'm slowly recovering from my financial loss and looking to get my plates cut.


Re: Size & Shape of Coils

PostPosted: Sat Sep 11, 2010 8:51 am
by windgat
Hi Easyas. I use 6mm plates, and with the holes cut (still need to be tapped or drilled out to accurate size) I have some here I can let you have for R100 a plate if yo come and get them. In my design, you will also need two bearing rings, which I also have here (R45 each).

Re: Size & Shape of Coils

PostPosted: Tue Dec 28, 2010 9:41 pm
by easyas
Hi Windgat

Still around and working on my wind Gen. Did test on my three blade vawt today and seem pretty good.
I have changed my plans some what, I want to first build the mechanical drive systen then adapt the coils
that I have built and then buy and fit the magnets.

Will chat to you on the magnets at a much later stage.