Coils wound in pairs using 2-in-hand 1.6mm diameter wire. Each coil has 37 turns in the one we did for the workshop.
Coils in each pair are roughly ‘in phase’ if one is flipped over as shown. (Actually there is still 30 degrees of electrical phase difference between them, so they are each 15 degrees off the total combined phase angle, which means about 3.5% loss of voltage.)
Pairs that are opposite to each other are ‘in phase’ if connected backwards as shown above. Then the phases are connected in star by linking all of the starts to a neutral (black wires).
This alternator uses 10 poles made from ferrite magnets. When magnets are fitted tightly together like this it makes sense to me to use smaller coils with smaller holes and benefit from the shorter turns in each coil. It’s fun to try something different anyway.
The same winding could work with 14 magnets. But I see no merit in doing this. Maybe somebody can? The inner turns would get more induction from smaller poles, but there would be more leakage flux.
Good Day Hugh,
what is the calculation behind 10magnets, 12 poles? how many coils if it is 6 magnets?
Vw
The calculation is a bit long winded but there is some discussion of the numbers here
There is no simple answer to “how many coils for six magnets” as this depends on the magnet shape in relation to the alternator as a whole but you could for example have 5 coils arranged in a 5-phase stator. doing a 3-phase output is harder.
thanks hugh, the magnets are ferrite and its 6″ x 4″ x 1″ in 17.2″ OD plate, outer dia gap will be 7″
Yeah i am following this thread, after this only, again thought of making use of those magnets.
copper wire thickness, is 14awg.
vw
Hi VW here is a picture of 9 coils on your 6 magnets. Connections are simple – just use 1,4 and 7 for one phase and so forth. No need to reverse any connections.
I’d suggest you get bigger disks (19 inch diameter) for this project.
Hi,
What will happen if i wind it this way but use a 12 pole as well (12 pole, 12 coil). Would it work even phasing is the same?
If you use 12 poles and 12 coils then this will be a single phase alternator. You will need to reverse the wires on every second coil. Finish of coil 1 is connected to finish of coil 2, start of coil 2 to start of coil 3 etc. It will work well but you will get some vibration/noise in the machine and there are other advantages to 3-phase.
Actual coils and poles were designed as a single phase, 1st coil connected to the 2nd, 3rd up to the 12th coil winded alternatively. Since pole modification is of my limitation right now, would winding the coils like of a 3 phase (preferably delta connection) produce more power output compared to the output of the original winding connected in series up to the 12th coil?
please send connection diagram of 12 magnets and 9 coils connected in 3 phase connection
hi
You can find a diagram at the end of this one
Hugh
http://www.6pie.com/images/flatcoil.jpg
Hi, are you having any problems when one magnet passes over both sides of same coil?
hi Lauri
That’s a good question, and in the past to be honest I would have thought that this would be a problem. When there is one magnet on both sides of the coil, it’s induction is indeed cancelled out. However this only happens during a certain part of the waveform when the voltage is low anyway. I would not say it happens when the voltage is anywhere near its peak, which is when the coil is conducting current.
That’s my explanation but whatever the reason I seem to get good results with these smaller coils.
The main advantages of smaller holes in the coils are that I can fit more coils with wider legs into the same space so more coil turns of wire, and at the same time the turns are shorter so the resistance is less. It’s a new way of thinking for me since I would have always said you should go for the maximum voltage by using a large hole in the coil but I am finding out that this way works well for alternators with magnets that are closely packed together, and the ferrite magnets are cheap enough to do that.
Hugh
respected sir
i am making axial flux generator of 16 pole AS i am refering ieee paper they have mentioned three phase stator winding
double layered full pitched ..
no of coil 48
turns per coil 7
thicknesss of the winding is 5mm
can u please help me .. i m getting confused as 16 pole and 48 coils so one pole would cover 3 coils
could u please make understand with drawing of three phase stator with pole and winding connection
sorry i had put some data misssing tht is..
outer diameter of rotor 200mm’
innner diameter of rotor 110mm
thickness of magnet is around 6mm
please help me out …
hi Mallikarjun,
the winding has overlapping coils, I would say and they are large. Full pitch coils means they span from the centre of one magnet to the centre of the next.
Distribute them evenly, and you will find that you have 3 phase groups that match the pattern of magnets at different angles. Connect the first coil to the fourth and the seventh etc. That is one phase. 2nd to 5th and 8th is the next.
You will need to reverse every other coil, so swap the wires around on coils 2,4,6,8, etc. Then connect all the coils in each phase in series and connect the phases in star or delta as you wish. I prefer star.
I hope this helps? Hugh
sir
i taught that in double layer the winding would be laid side by side first phase R and R’ would be connected 6 and 7 of R and R’
and other phase would be connected to Y and Y’ would be connected to 8 and 9 of Y and Y’
AS it is axial ..
then
6×48/48 =6
so R – 1+6=7
R’-2+6=8
so on for other phase ..
please help me if i am wrong sir
and the above i stated will be for 8 pole and
magnet would be of NdFeB magnets in trapezoidal shapes with curvatures
magnet dimension would be of
outer diameter-60mm
inner diameter -47.5mm
height – 39.5mm
thickness -5mm
so the
rotor diameter would be 220mm
rotor inner diameter would be of 140mm
the stator coil would be connected as i stated above … does it work …sir
Sorry Mallikarjun but I can’t follow all this. Please email me with a full description document of some sort.
hi this mallikarjun i m making a generator ,”axial flux permanent magnet generator ” of 230 watts using Ne-Feb magnet of 42 grade ,
i have designed a rotor of outer diameter 236mm and inner diameter 116 mm
magnets shape is trapezoidal of 60mm in height and 47.5mm x 39.5mm top and bottom in length ..
i m using 8 pole rotor single sided not dual rotor so..
i need design the stat-or using toroidal coil winding three phase star connected single layer ..
i dont how to calculate the number of coils need and and number of turns per coil and thickness of wire to be used
for toroidal coil … pls do help me out ..
hi Maddy,
I’d suggest you use 24 coils on a toroidal core. Watch out for high thrust loads on the bearings. Before I can suggest a number of turns I’d need to know 3 things:
Type of magnet (NdFeB grade what or ferrite?)
Operating voltage
operating speed (rpm)
YOu can use trial and error instead and just wind some test coils to collect data and work from that. It’s the safest way in the end. But I can do some calcs if you give me all of the necessary information.
Hugh
thank for ur reply .. we are using neodymium magnet or rare earth magnets of grade 42 … not ferrite
magnet to withstand maximum temperature is represented as “grade” in my case 42 grade withdstand upto 180 degree Celsius..
Operating voltage.. 100v
operating speed (rpm) ..400rpm
please let me know any more information need …
There is a section at the end of my recipe book that explains how to design alternators. The toroidal one is a bit different because the coil presents only one leg to your single magnet rotor, but the equations will work in an adapted format.
total flux = magnet area A sq.m x flux density B (Tesla)
turns n = turns per coils x coils in series/phase
revolutions per second = rpm/60
Average voltage (which is 100/2.72 for star connected AC)
= total flux x number of turns x revolutions per second
= A x B x n x rpm/60
n=60 x V /(A x B x rpm) = 6000/(2.72 x 0.02 x 0.7 x 400) = 400 turns total
If this has 8 coils/phase I would say 400/8 which is 50 turns per coil.
There’s a bit of guesswork in there because I don’t really know the flux density.
sir dont we use average E=4.44* total flux x number of turns x revolutions per second
please let me know if i m wrong
sir
for star connected we use 100/1.732 but not 100/2.732..
i think we made missed typed
total flux = magnet area A sq.m x flux density B
=2160 x 10^-6 x1.29=2.8mwb..
Average voltage (which is 100/ 1.732for star connected AC)
= 4.44 x total flux x number of turns x revolutions per second
= (4.44 x 2.8 x 10^-3x number of turns x 400)/60
= 696.6090 turns total
8 coils/phase =696.6090/8 which is 87 turns per coil.
so i can take 88 turn per coil …
so can i use this one sir..
please let know sir if i have made any mistake ..
hi this Maddy,……. can u please the coil winding connection for the stator …as it 24 coil .. 3 phase 8 pole machine .. that is 8 coil per phase .. as the inner and outer diameter are 236 and 116.. please can u shown the diagram how it can be connected ….
sir let we know the above calculation i have made that are correct or not .. as i’m student there is no noe to guide me .. please assist me..sir
Maddy
hi Maddy,
I quote from the bottom of page 55 as follows:
“(Average voltage is a little lower than the RMS value that we commonly use to measure AC voltages.)
So the output voltage from the thee-phase winding will peak at 2.72 times higher than the average voltage for one phase. (2.72 = 1.73 x 1.57). ”
We are looking at the peak voltage and not the average so that is where the 2.72 comes from.
I hope this helps.
Hugh
thank you sir.. for your kind reply
can i have some sort of pdf or copy of your book .. for reference purpose.. that would be very much helpful for us ..
thank you
maddy
My recipe book is available for only $5 on Kindle.
http://www.amazon.com/Wind-Turbine-Recipe-Book-ebook/dp/B003XVZADA/ref=sr_1_9?s=books&ie=UTF8&qid=1280727133&sr=1-9
Anybody can download it and if you don’t have a kindle you can also download a kindle reader for your computer from amazon too.
sir i do hav this edition
Hugh Piggott A Wind Turbine Recipe Book The Axial Flux Windmill Plans Jan 2009 Metric edition
i want to know more about 8 pole 6 coil diagram and
calculation part .. i want make this one
please help ..
sir
when u would be online .. that would more help full for us to chat with you and clear your doubts..
hi Maddy,
I am online most of the time I guess. I try to answer your questions. You can also email me. I don’t know what your doubts are this time. I am busy, so please ask simple, clear questions. If you tell me ‘I want to know more’ then I will not take time to answer. You have to tell me exactly what you do not understand.
Hugh
Hello !
How important is the weight of the Tail Vane and the angle of 20 deg at the hinge?
Regards,
Bipin
The weight and the angle of the tail will both be important in determining how the turbine furls. if they are too small and light then the output may be a relatively low, especially as the wind gets stronger. On the other hand if you increases them beyond a certain point you will burn the stator or cause some other problem.