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.

Hi Hugh, great website. Is there an optimum size of coil winding compared the the dimensions of a neo magnet? For example if I have a magnet that is 30mm in diameter and 10mm thick. I understand that the coil will be wound to have an inside diameter to match the outside diameter of the magnet. So in theory the magnet could just fit inside the coil. What I dont understand is should I make coils that are tall and thin or coils that are short in height but thicker in diameter. For example, say I need 100 turns ,should I make the coil 10 turns high and 10 turns/rows wide or only 5 turns high and 20 turns/rows wide, or 20 turns high and 5 turns/rows wide? Does it make any difference?

Should the coil be the same height as the magnet?

hi Marc,

to be honest there is no simple answer and no ‘right’ way but some will work better than others. The spacing of the magnets will be just as important as their shape in determining the optimum coils shape.

Often a coil thickness similar to magnet thickness gives optimal results. Total gap between magnet faces similar to total thickness of the two magnets is a good rough idea for optimising the use of magnets.

I like to space the neos widely since they are expensive but if you want to maximise the power from a given disk you should cram them together, and this is what I do with ferrites. Then the hole in the coil can be smaller and this works well.

I hope this helps

Hugh

ok sir thank you… for your kind reply

reply for question 3

Normal we used for star connected

stator coil space = (3.14Dm/no of coils )

Dm mean =(inner diameter of rotor + outer diameter of rotor )/2

And stator coil space multipied by factor .85 we will get space for each coil ..each coil are placed at angle of 15 degree ..

and magnet were placed at angle 45 degree in the rotor

average voltage)=4.4 ( Phimax) x f xTph where f is frequency and Tph is the total number of turns per phasex.936

( 100/1.73)=4.4 ( Phimax) x f xTph where f is frequency and Tph is the total number of turns per phasex.936

(Tph)total number of turns per phase=103.908

Tph=ZxS/3

103.098×3/24=Z

Z=12 turns

instead of 12 we made 18 turns

we made this with 18 turns for each coil but we could get the voltage as the air gap between the stator and rotor was more than 5mm as stator mould was a bit more out of shape ..may be the no of turns were less

so couldnt complete the project so we trying with different stator coil design

.

Let us now consider the design of 6 coil and 8 magnet

magnet dimension =43.5X60

thickness=5mm

Average voltage= 2xtotal flux x number of turns x revolutions per second

magnet area A sq.m=.002610

no of magnets=8 so..

Total magnet area A =.00261×8=.02088

flux density=N42=(Br) rem-anent flux density =.65

flux=.02088x,065=0.01357

Average voltage= 2xtotal flux x number of turns x revolutions per second

(60/2.72)=2x.01357 x Nx 400/60

N=121.91 approximate 122

for two coil per phase N will be 61

but in your calculation sir \

Question

B you have taken as .3 as flux density=N40=(Br) rem-anent flux density =.63 do we need to take it as .3 itself any reason for that

since i m using the single sided rotor not a dual rotor ..so the magnetic flux cutting the coil would be less so do we need increases the number of turn ?? if so mean.. by much ??

what is the air gap that we have to maintain between rotor and stator would

waiting for your timely reply

Thanking you

Mallikarjun(maddy)

hi Maddy,

I do not understand much of the above since it is mostly numbers and no clear explanation of where they come from nor where you are going with them. But I can expalin why the example in my book uses B = 0.3. This is because the example is the 1200 turbine which has only one magnets rotor (single sided). In my experience this has B=0.3 T.

And yes if you have taken B=0.6T then you will not have enough turns and you may have to double the number of turns to get the right speed. This will make the resistance four times higher.

Hugh

i want to know 6 pole single phase generators connection plz tell me about it with dia gram also

if you want single phase then the simplest scheme is to use 6 coils for the 6 poles. However the coils are not actually all in the same phase if you simply connect them in series. You will have to reverse every second coil. So the connections are:

Start of first to output wiring

finish of first to finish of second

start of second to start of third

finish of third to finish of fourth

…

finish of fifth to finish of sixth

start of sixth to output.

I am planning to design one alternator with 100mm X 12.5mm X 12.5mm

with 10 pole on a stator with rpm 900. What should be no. of coil, wire for coil, size of coil

for output of 50hz 230volt 4-5kva.

my magnets were N35.

Please let me know.

hi Rajeev

This type of alternator is unsuitable for producing 230V 50Hz. Also the 10 pole will produce 75 Hz at 900 rpm. I also doubt that you can get as much as 4 kW from this size alternator at this rpm. It’s much too small. sorry

Hugh

1 KW @ 220 Volts & 750 RPM with 10 N35 Magnets , Pls suggest what will be the best possible values of Number of Turns & coil dimensions.

you could try 400 turns and connect all four coils in series for each phase. It’s a rather stupid shape of magnet to start with though. YOu might get 1kW at 750 rpm 62 Hz or it might burn out. YOu’d need a large rotor to make room for thick enough wires.

I am trying with 600 rpm to get 50Hz, but I want to know the dia of winding wire for 400 turn as advised by you

Hi Rajeev,

You need to look at the rotor diameter and figure out the coil spacings and hence the cross-sectional area available for wire and hence the wire size from there. It’s all documented clearly in my Recipe book so I suggest you have a read of that and then get back to me with any questions when you have done some reading.

Any one can help me with a single phase output AC when i use a 8 poles and 8 coils?

All result i’ve got is 2.++ V(AC) and current around 0.5 to 1A(AC). How can i increase the voltage and current up to 6V and 1A by using:

•Copper wire SWG 23

•200 turns per coils

•parmenent magnet type N48 (square shape)

•size: stator 6.5″. Gap between each magnet 1.3″..

Please anyone reply my question as soon as posible.

Thank you guys!!!

hi Safwan,

YOu get more voltage and current by turning the altenator faster. Check that you have the coils correctly wired. If you are using single phase then you connect the coils in series for more voltage. But you have to reverse the connections on every second coil as it produces the opposite voltage. So connect finish of 1 to finish of 2, start of 2 to start of 3 etc…

Hugh

you mean for first coil in clockwise and second coil in anti-clockwise and the connection finish of 1 to finish of 2 and start of 2 to start of 3(clockwise)?

If you make the connections that I suggest then the effect is to reverse the direction of the turns. If you reverse the turns (turn coil over for example) then you do not need to connect finish to finish etc. Just connect finish to start of next one if you are turning every second coil over.

Hi Sir, you know what? I’m very thanks to you about this discussion. with all clockwise direction I can produce more than 6V, now my output voltage arround 10-13V.

I use connection all in clockwise, finish of coil 1 to start of coil 2. finish of coil 2 to start of coil 3 and so on until at last coil of 8. Finish of coil 8, it was my output(-).

But sir, what is the different between both connection? All my research I do, every connection must be in clockwise and anti-clockwise (forward and reverse). And Sir, I use formula, I=V/R to get the current value, it is the right method to get the current?

Can you explain to me about this situation?

I really appreciate your help. very very very appreciate.

when making a single phase stator (which I don’t really recommend) with the same number of magnets as coils, you will have half of the coils under north poles while half are under south poles. So they will produce the opposite voltage and you have to reverse the sense of the coil, or its connections.

do you mean all in same direction of coil is wrong?

If all the coils are wound in the same direction, and you have equal magnets and coils like this, then you need to reverse the connections to every second coil, or the voltages will cancel out and a well made machine will produce little or no output.

thanks you sir for your time.. may have a nice day.. hehe

Dear Sir(Admin)

I am a student and interested in Low RPM PMG. Through Google I had been searching for some designs for 5kw PMG for river current and I got a link which led me to this discussion board and now I know what to do. Thanx for all.

But what is your idea to get constant frequency suppose at 50Hz when RPM of the turbine varies in a wide range from 50 to 200 RPM??

I will be glad to being answered by you.

Thank you sir.

Use an inverter if you need constant frequency. Rectify the output to DC and inverter again. You will also need a battery or a grid connection to stabilise the situation.

Dear Sir,

I appreciate that you are among rare people who works on axial flux generator.

I am going to design 500W generator for vertical axis wind turbine.

I have used 23 gauge wire.

12 coils (wedge shape) having 130 turns each, application battery charging 12v/3amp.

We are using N48 grade neo. magnets

I request you please suggest below things.

Shape of the magnets:

Starting Torque required for the generator:

Let me know if we need to change upper selection done yet:

Although we have given order to our library department to purchase your recipe book for reference, but we also need your expert advise.

Thanks

Hi Shahid,

This is backwards. it’s better to start with the 12V 3A specification (and you also need to know RPM), then choose magnets and finish with the design of coils, wire size and number of turns.

Personally I think you are wasting your time with vertical axis but the funny thing is that almost everyone does this, so I am not surprised.

Let me know the rpm (for cut-in, and also for full power at 40 watts electrical) and also the size of the coils if you have already wound them.

Starting torque will depend on the seals in the bearings. There is no torque in the magnets and coils until you start to produce a current.

I hope this helps.

Hugh

Dear Hugh,

Thanks for the suggestion but we are in a project and need to design vertical axis, and torque issue is cleared from your ans.

Coils are not an issue I can make it again easily,

Cut in speed is 3m/s and rpm is around 70rpm.

coils are WeDGED shaped type, 130turns, having wire dia. 0.574mm, wounded on 30mm top length and 10mm bottom length.

I want to know the design procedure for it.

Is your book is helpful for such design.

If not please suggest,

My recipe book describes the design process completely from page 54 onwards. you may need to use some trial and error to find the best size and number of magnets. But it will help if you use the 46 x 30 x 10 ones in the recipes, which are also widely available.

70rpm is very slow, but the power is also very low so the rotors should not be too large. Get back to me with any questions.

Have fun

Hugh

I will get back to you when completed.

Thanks……………………

Hi Hugh,

Your wind power “Bug” has bitten me. I have 24 neo magnets 46 x 30 x 10 mm and 6kg of 1.6mm magnetic wire. I have made up two magnet plates of 6mm x 305mm, and fitted 12 magnets on each plate N..S..N..S placing. This info I got from ” Other Power” website. I then turned 9 x coils of 140 laps of 1.3mm magnetic wire, and did the castings. My problem is that I see good voltage, but very little amps. The machine is meant to give 48 volts. The blades are 3 x 1.5m alluminium. If disconnected from the batteries, I get up to 130 volts output. The coils are connected in3 x series/star configuration. As the wind speed increases, the battery (4 x 12volt 105 a/h) increses in voltage up to 62 volts and even higher, but very little amps. I have even replaced the amp meter. I first though the blades are stalling, but this does not seem to be the problem. I have a fairly good electrical back ground.

I would like to turn new coils for the machine with the 1.6mm wire on hand, that would give me as low as possible cut in speed, with good amps at higher speed.

Could you please assist me with this. What number of turns should I use per coil.

I will be ordering your metric book next week.

Regards

Hi

If you have volts but no amps this usually means a high resistance. Check each battery when on charge to see if they all go up to 15 volts? I suspect there is a resistance between the voltmeter and the batteries. Or the batteries are each and all high resistance themselves. Seek out where the voltage is going. That’s your high resistance.

turns per coil will depend on blade design. I make high speed blades but your aluminium ones may be rather slow. However this would be a voltage issue at first.

If you want to avoid frustration the best way is to read and follow my recipe book 🙂 140 turns should work for 48 volt output if you wired it up correctly.

Hugh

sir

For 750 rpm permanent magnet alternator 1 kilowatt (8 poles)

what should be the wire guage & connection & stator width length & slots

please send me details to my email address

mohdy246@gmail.com

yousuf India

hi Yousuf,

I’d need a bit more detail for this including the size of the magnets and the desired output voltage.

Hugh

very helpful

Hi sir .. Your blog is really helpful in constructing PMA.

i am trying to build up a permanent magnet alternator which can run in low rpm ..

I need your suggestions for 2 KW or more output setup for home use ..

I have 24 neodymium disk magnets N38 grade, having diameter of 30 mm and 5 mm thickness.

please suggest me the the setup of coils, wire guage, no of turns per coil, no of coils or any thing which may help ..

I have been thinking of dual flux permanent magnet alternator ..so that 12 magnets on each rotor disk and stator sandwhiched in between.

I have setup the basics now just stuck upp on the stator. confused relating the winding stuff ..

please suggest me proper solution ..

hi Syed,

To be honest it will be difficult to get 2kW from these magnets. You will need to run at quite high rpm. If you want 2kW at low rpm it would be better to use more, larger magnets. for example you could use the design for the 4200 mm diameter machine in my Recipe Book. It can produce 2kW at 300 rpm. But it needs to be well cooled by the wind to work like this.

If you need 220 volts for home use then you will need to use an inverter. The alternator will produce 3-phase power with variable frequency and normally you would charge a battery or connect to an existing grid using a grid-tie inverter.

Hugh

thanx for your reply sir.

is their any possibility .. like if I could use double magnets on each rotor .. i mean 24 magnets on each rotor (one magnet attached to another forming 12 pairs on each rotor) .. as neodymium magnets are magnetised through thickness .. so that if I attach two magnets together so their flux would increase ..

48 total magnets on two rotors ..

***from above

the desired output voltage is 220 volts for home use ..

Sir !! please guide me regarding the above query ..

hi Syed,

Even doubling the magnets will not reach the level you need. I’d say you need about 6 times that magnet volume to do what you describe. Also you need to study the question of supply voltage. You need to understand the need for storage in the system if you are not connecting this to the grid. So you will need to have a battery. Then you can produce 220 volts from that battery using an inverter.

I hope this helps. I’d need to know a bit more about what you are doing before I can help in any more detail. You want to run at low rpm but that is pretty vague and you do not say what is driving it.

Hugh

I’m looking to build a low RPM 12V DC generator. I would like to build one that has two revolving groups of magnets turning past a group of coils stationed between the two groups of magnets.

At moderate RPM’s I would like to see an amp or so. I would like to charge a battery bank and am not very interested in an AC generator because of the required step down rectifiers needed. I would rather create power that can be stored as is.

I can not seem to find clear answers on how many magnets, what size magnets, how many coils of which size wire, how many turns on each coil and how the coils should be wired together.

Your help would be greatly appreciated.

Thank You, John

hi John,

When magnet move past coils, they produce AC voltage in the coils. If the coils themselves rotate past magnets then it is possible to switch this to DC using a commutator but by far the simplest way to get DC is to use a rectifier. So I suggest you generate 3-phase AC and rectify it to DC with a bridge rectifier. This will not reduce the voltage by much and is much simpler and more reliable than a commutator.

My Recipe book describes how to choose the magnets, wind and connect the coils and so forth. There is even a section on how to design the alternator near the end of the book, but you should not need it. If you have a specific cut-in rpm in mind for 12-volt battery charging them I can help you design a suitable alternator based on one of my standard designs or using magnets of your choice.

Have fun

Hugh

Hugh,

I have bookmarked your book page just in case. I certainly appreciate your incredibly quick and informative response. I honestly figured I’d be lucky to have an answer inside of one week.

I have built several where the coils spin within a field and commutators pick up the power. I have made a couple of cool machines and one pair of AWESOME commutators. These are small though and put out from .01 to .03 volts with RPMs so high that coils balloon out and commutators take a viscous beating.

I really like the design type that I mentioned previously where the coils are stationary between two magnet boards and the coils are hard-wired instead of using commutators.

Well I guess it’s time to build and rectify me some 3-phase!

Thanks again Sir,

John

p/s i need help,for 20kva alternator with 6 coil ,swg 17 1/2,7wires in hand, 0 to16 all round of 5 coil.how to connect is a little bit difficult?

hi

I need a bit more information. I think it will need to run at very high rpm to produce 20kVA!

But it’s important to know the size and number of magnets, the desired voltage, the number of phases, the RPM of operation, and whether it is on a wind turbine (well cooled by wind). You need to tell me all these things or at least most of them and I can begin to help you.

Best

Hugh

Hi Sir,

Am currently doing 3 phase brush less DC motors project,16 poles ,18 slots i want to know how to determine number of turns per slot the winding scheme is AaABbBCcCAaABbBCcC.

It might be a trivial question to ask but please help me out.

Thank you in advance

Regards,

Shruthi

hi

Sorry I can’t help as I have no experience of the type of machine you are designing.

Hugh

Hi Sir,

I found a formula after a lot of searching but i didnt understand how it is derived and is it a standard formula

here is it

Turns per phase = 17000 x (System voltage V +1.4) / ( Desired cut in speed RPM) / (Strength of flux in Tesla) / (total area of magnet face in square inches)

can anyone please explain it?

and total area of magnet face means the area of magnet it is facing the stator?

magnet dimensions:

2.5cm length,and 2.2cm height thickness 7mm

so area of magnet facing stator is 16(poles) X 2.5 X 2.2=88cm2=>13.6sqinches

is this right way?

hi Shruthi,

That formula is a guide for designing an alternator that will charge a battery (at “system voltage”) via a 3-phase rectifier. I am not sure how useful it can be for designing a motor. I have never designed a brushless motor so I cannot help you there.

Yes the total magnet area is the area of magnet surface facing the stator on one of the two rotors. So if you have 16 poles on one rotor then you are correct.

Hugh

Good Day Sir. I am now working to make a permanent magnet generator with a 8 inch diameter rotor and 9 inch diameter stator. The rotor will have 10 magnets with 1 inch diameter and 1/2 inch thick. While the stator will have six coils. Will this generator creates great output. I am worried because the gap between the magnets is 0.6 inch only. If the rotor with magnets rotates through the coils there will be two magnets in one coil. I saw a picture above that the output will be cancelled out if this happen. Is this true? Thank you.

hi angelo,

I don’t understand why you only want to have 6 coils. You are right that much of the magnetic flux will be wasted in cancellation and the length of the turns will be excessive and the number of coils only few. So I don’t think this is a great design, no.

Hugh

But will this design creates an output for a 50 watts per 12 hours?

Hello Hugh. Thanks for the response but if I will make the diameter big enough will that be great?

For example. 10 magnets with 6 coils and a diameter of 12 for rotor and 13 for the stator? Thanks i just need it very bad. Thanks a lot.

HI Angelo,

I don’t know what else I can tell you. 10 magnets is not a great idea. 8 magnets and 6 coils is a good combination, yes. It’s the classic ratio 4 to 3 which I almost always use. Go ahead and do it that way. I cannot promise you will get 50 watts without a whole load more information about what you are doing such as the type of magnet, the turns per coil, the system voltage, the rpm, and what you plan to use to drive it. Have fun.

Hugh

I just need a 50 output for that will that be enough? Or can i make it 8 magnets with 6 coils though?

Sir,

Please may I know the best type and shape of Magnet to use with a Triangular Coil or say Trapezoidal?

I am not building a Wind Turbine. No. My project is totally different. But I need an High Output Power to achieve my main aims.

I am having 2kg of 1.86mm thick Enameled Copper Wire.

Also, is the Trapezoidal shaped coils MOST effective or the Rule of Center Wideness of Coil to Size of Magnet the most important issue?

I mean if my coils are Circular in shape and are 70mm Outer Diameter and 50mm inner diameter, must I use just use 50mm diameter magnet?

Is Triangular or Trapezoidal coils the most efficient shape?

Can a Block magnet be used over a Trap. Coils?

Will the output efficiency be the same with if Trapezoidal Shaped magnets were used?

I am deeply curious sir.

hi Dare,

The best coil shape depends on many factors. If the magnets are widely spaced then I consider that it’s best to have a hole in the coil which is the same shape as the magnet face. But to be honest you can often get more copper into your coil by making the hole trapezoidal so it is smaller at the inner end. As the magnets get closer together it becomes attractive to use a triangular hole in the coil.

I like to study the way that the coil legs move through the magnetic flux. Of course the flux itself is not uniform nor does it have sharp changes in density. But if both legs of a coil are under (different) magnets at the same time then I consider that this will produce a good peak voltage.

A trapeziodal magnet is a good thing but only marginally so I don’t worry about that too much. You can get good results with rectangular and even with circular magnets. If you want to get the best out of your magnets then I would say use a large disk and space them widely. If you want to get the best out of your small disk then use many magnets and even trapezoidal ones and cram them in tightly. It depends on your goals.

Hugh

Thank you so much for your surprisingly timely reply.

“If you want to get the best out of your magnets then I would say use a large disk and space them widely. If you want to get the best out of your small disk then use many magnets and even trapezoidal ones and cram them in tightly. It depends on your goals”

By cramming, do you mean I should place my magnets on rotor as is was done here => http://xindaenergy.en.alibaba.com/product/1978948961-221458799/5kw_150rpm_axial_flux_permanent_magnetic_generator_PMG_for_vertical_wind_turbine.html ??

yes this is crammed in all right.

I do not like the stator inside the casing like this. It will not be well cooled. When it gets hot there is a danger it will detach from the shaft in the centre. It’s more reliable to support the stator at the outside and allow cooling air to flow over it.

Hugh

Alright. I do not intend to use that type of design. I plan to use Cardboard Sheet and Plywood for my Rotor and Stator respectively with Split Stator Method.

So this allows for pure ventilation and constant cooling.

Now may I know if I can use Block magnet over Trapezoidal or Wedge Coils?

If my Stator is 30cm wide, what type of coil shape is best to use over it?

Wish I can show you some pictures of what I have done so far before I contacted you.

How can I do that?

yikes I never heard of cardboard rotors before. But have fun!

Use the magnets you can get. Trapezoidal is too expensive for me, with very little gain. Block is fine for me.

Coil shape depends on how close the magnets are together. If they are quite close together then I use triangular shaped coil formers.

you can send me pictures by email of course.

hugh@scoraigwind.co.uk

Hugh

I today sent the pictures.

Do you mean it is best to use Block magnet over block coils?

Will it not be better to use Vortex connection instead on connecting the coils in phase?

Vortex connection means using Eleg eletrolytic Capacitors and Diodes to collect power from each Coils and later connecting the coils in Series or parallel Series or parallel using Diodes and caps again?

sorry I do not know about vortex connections but using capacitors and extra diodes is all going to increase your losses. I’d suggest you keep the circuit simple.

Hugh

Sir what is the use of using diamond shape coils in armature winding

The actual coil will develop a rounded shape as you wind it. You can start with a round, square, triangular, diamond shape or whatever but it will go more and more toward round as it builds up.

In my opinion it depends on the spacing of the magnets somewhat. If they are far apart then I like to make the hole the same shape and size as the magnet. If they are close together, then I prefer a triangular shape to start on. I have seen Otherpower make coils with a sort of diamond shaped hole. All of these will work. The goal is to get as many turns of wire, as thick as possible, interacting effectively with your magnets. I think a triangle works better for axial flux machines than a diamond but the difference is small.

Hello, i really like a lot of the projects you and your people put together and work on,amazing and i’ve been all over the net looking and shopping for a 5kw grid tie vertical wind turbine from China to Alaska and also had a look at many do it yourself projects.

For my first project i have 3 LG 36 pole stators & rotors or direct drive permanent alternators after looking all over the net for different ideas on what i’m gonna make i came to a final decision that i’m gonna make a (dual stator & rotors) vertical wind turbine with the same bracket or mounting method as (Marijanka Jelic) on youtube.

I believe the way he did it is pretty much the best rather you use it as a vertical or horizontal and i also know that turbine is only going to give me a maximum of so much power witch is much less than a 5 kw system and the reason why i’m writing today is because for my main project i decided that i would be happy with the (5kw Wind Razor vawt kit)i’m trying to get in contact with them to buy the complete diy kit but i haven’t been able to make contact with any sellers i know i will have to make my own coils and stator and buy the Neo magnets,i tried Windgenkits.com and Wind2Volts still no contact i don’t know if the kits a discontinued one way or another if i must make it from scratch i will.

I you have any contacts for me to reach them could you please send it to my Email.

I know they are somewhere down in the states,,,addresses,phone number,emails or anything that would help me reach them i’m in New Brunswick, Canada thank you so much.

Dan……………..

Hi

Thanks for the message.

I have no knowledge of any 5kw Wind Razor vawt kit nor do I wish to hear about it as it will just be another depressing ripoff. I don’t know why people keep thinking I am keen on vertical axis projects. It’s driving me nuts.

I do NOT recommend that you build Vertical Axis.You are wasting your time. Please go and do it somewhere else if you must 🙂Hugh

Hi dear admin

Sir I need your help. I am going to make wind turbine generator I have a ABB Motor that is 15Hp 3 phase 380v 50hz 1400 RPM And Total Statot slots is 48 . I want to covert in 12kw 3phase 380v 50hz frequency. Am want to use N52 50×25×12mm Rare Earth Magnet so original winding I will remove and I want to rewind again for 8 pole stator that is 8 coils per phase 8+8+8=24 and 12 Magnets on the rotor . Witch wire gauge i have to use for rewinding of stator. Ist I will use single turm method then how much volts I get on 500 RPM then I will make coils .but sir I am confused in winding pitch. Should I used slot number 1 to 4 7 to 10 plzz sir tell me this is correct or rong.tell me online witch wire gauge shoud i used for 12kw 3phase 380v 50hz frequency 500 RPM. I will w8 for your reply.

Hi dear admin

Sir I need your help. I am going to make wind turbine generator I have a ABB Motor that is 15Hp 3 phase 380v 50hz 1400 RPM And Total Statot slots is 48 . I want to covert in 12kw 3phase 380v 50hz frequency. I want to use N52 50×25×12mm Rare Earth Magnet. so original winding I will remove from stator and i will rewind again for 8 pole stator. that will be 8 coils per phase 8+8+8=24 Total coils will be 24. And 12 Magnets i will use on the rotor . Witch wire gauge i have to use for 12kw 3phase 380v 50hz frequency. And sir that orignaly rewinding is 4 pole.so I want to make 8 pole stator and 12 pole rotor. I will use single turn method then how much volts I get on 500 RPM then I will make coils .but sir I am confused in winding pitch. Should I used slot number 1-4 7-10 plzz sir tell me this is correct or rong.Plzz tell me witch wire gauge shoud i use. And how many wire shoud be inhand to make a coils. for 12kw 3phase 380v 50hz frequency 400 to 500 RPM. I will w8 for your reply.

hi Umair,

I do not have experience of converting induction motors to PM alternators. I know that this is often done in Holland. Maybe try asking Adriaan Kragten?

8 poles will give you 50 Hz at 750 rpm. There is no slip so it is exactly that speed. But I will say that you cannot get 12 kW at 750 rpm from a motor that is designed to work at 1400 rpm. You can put 8 poles into it but the flux change will be less and so the coils will need more turns of thinner wire and so you will not be able to get the same power output. It’s a rule of electrical machines that to obtain the same power at lower speed they need to be bigger and heavier. If you go to 12 poles and down to 500 rpm then the power output is lower still.

Did you know that you can use an electric motor as a generator simply by adding capacitors to it? Maybe get a big 8-pole motor and add capacitors instead of magnets?

have fun

Hugh

Hi Admin,

i like your information and comment on this website. I have been planning to make 1 phase axial flux generator with data as per below :

1. Output 220 Volt AC …. 50/60Hz

2. With 6 poles coreless using 1 mm diameter wire (or may be more than 1mm).

3. RPM is 5.000 until 10.000 RPM ( yes, five thousand until ten thousand RPM)

4. Magnet using neodymium from PC Hardisk with thickness is 5 mm (dual pole each surface).

Is it possible to produce 220 volt? if possible, how many turn wire each pole? how many magnet i need?

note : i didn’t have any difficult to get 5.000 ~ 10.000 RPM. my understanding much RPM will produce much electricity, so i want to make 1 phase axial flux generator using this speed….the important things is i need 220volt output using 6 poles…please give me suggestion sir.

hi Bambang,

It’s not hard to make 220 volts using plenty of turns per coil. If you want me to calculate a voltage or specify a number of turns then you would need to

tell me everything in detailincluding the size of the magnets and the whole layout of the alternator. If you want 50 Hz then you can do this with 2 poles at 3000 rpm but you cannot go faster and produce 50 Hz. For 60 Hz the 2-pole speed is 3600 rpm.Bear in mind that speed alone will not make power. You do need to have some torque behind it, and so there needs to be a power source driving this.

have fun

Hugh

Hi Hug, thank you for your fast reply i am very appreciated. i am trying to give you more detail of my plan here :

1. Magnet size = 45mm x 17mm x 4mm (thickness) with dual pole every surface…( my plan will use 8 Pcs, give me suggestion if possible less than 8 Pcs).

2. Alternator : only one plate rotor for magnet with diameter plate is 18 Cm and one plate for coil (stator) with same diameter … so, only one plate surface usage for each plate.

3. For speed (RPM), i can adjust from 500 ~ 10.000 RPM constantly, and i have special unit for controlling speed. so i think doesn’t matter about speeed ….even with or without load the speed still can adjust constantly (please correction if i am wrong).

4. Coil as per my plan will use 6 coil ( located on plate : every 60 degree distance each coil).

5. Wire diameter minimum 1mm, please give me suggestion for better wire diameter size.

would you please calculate for me how many turn each coil?

If any additional detail information out of these, please let me know. Thank you very much

hi

Just to be clear, are these bard drive magnets with two poles on each face of each piece? So with 8 pieces you will have 16 poles?

I wonder why you have chosen to use 6 coils? If you want single phase then the number of coils should be the same as the number of magnet poles?

I need to get all this sorted out before I can help

Hugh

Yes correct, i have HDD magnet 8 pcs with dual pole each surface, total 16 poles each surface..if total magnet equal to total coil for single phase, meaning i only need 3 pcs magnet for 6 coils right? with magnet distance each other is 120 degree.

But in my imagine, if magnet distance 120 degree each other, meaning the distance of each pole (between N & S) will not same because 1 magnet having 2 poles…it will create problem or not? (Because as per usually single phase sketch having same distance each pole (N & S distance is same each other) following magnet distance because using mono pole magnet each surface)…please give me suggestion if better using mono pole magnet i will buy new one.

The reason why i chosen 6 coils because that is maximum availability number of coil i use following outer diameter 18 mm. (possibility outer diameter stator plate can i use is only 18 mm)..if possible using less than 6 coils is better.

Please help how many turn each coil if i use 1mm diameter wire? if 1mm is too small, please give me suggestion better diameter wire size and how many turn each coil.

Is it require double layer wire each coil or only single layer?

-Bambang-

hi Bambang,

I suggest you consider why you want to get 50 Hz out of this thing. Because yes that does severely limit the size it canbe with your hard drive magnets. And yes you would find it much easier to build a good alternator with 6 individual pole pieces about 30×30 mm.

Hugh

sorry i have some correction here, i mean 6 coils… not 6 poles …. how many turn each coil and how much maximum watt can produce with 220 volt output?

Hi Hugh,

Thank you for your suggestion, i will back to you when i find the magnet size depend on availability here. my i know your email address? my email address is : lupuzmillenia@gmail.com … hope we can keep in touch through email also.

How about magnet thickness? any suggestion minimum thickness?

-Bambang-

I have found new size magnet available here, they are : neodymium magnet diameter 25mm x 2mm (thickness)…. my plan i want to produce electricity like home electric (220 volt with 50/60 Hz), would you please calculate how many turn each coil? ( i still want to use 6 coil).

hello dear

i want to make a 3 phases PMG using 16 poles of microwave magnets and 12 coils of 1.6mm copper wire .

can u help me to chose better design and get max power ??

waiting your reply

thank you.

i have a question , in permanent magnet motor 3 phase star 48 slots 20 pole how can get 20 poles in 16 coils per phase r phase coils are not connected sequencialy please help me

selvanathan /india

sorry I don’t know.

Hugh

we supply 8poles ring magnet for Hitachi Co.,Ltd ,anyone want to know?

hello dear,

1) i have wound 48 turns of 1.68mm dia copper wire in one coil.

2) magnets are neodymium 50 x 25 x 12.7mm thk. N35.

3) coil is trapazoidal with id of coil matching the shape of magnets.

4) thickness of coil is 11mm.

5) i have fixed up one magnet on one mildsteel disc and another magnet on another disc.

6) the magnets are mounted with correct polarity.

7) thus there are two magnets and the coil travels between them.

8) i am turning the magnets on a lathe at 180 rpm.

9) i am getting ONLY 0.5 open circuit volts and 0.05 A.

10) could you please diagnose, what is going wrong.

11) i wanted to confirm – so i am testing only one coil with two magnets.

hi again, the corrigendum –

a) the coil is fixed on the ‘lathe tool post’and the two mild steel discs are turning together.

kindly send the reply.

hi

I don’t think there is a problem here. If you get 0.5 volts from one magnet per disk then you might get 6V from 12 magnets per disk. This is one coil. Using 3 coils in series per phase and connecting the phases in star then you would get 31 volts. If the voltage is AC then your DC will be 40% or so higher at about 43V dc for your 160 rpm.

I don’t actually think it will get that high. The waveform with a single pair of magnets is very strange and is probably fooling the meter. But if you want to learn then you need to fill the rotor with magnets.

Hugh

sir is the computation for VAWT and HAWT for the axial generator the same?

Hi Wil,

Yes you can use the same alternator for vertical axis but you will need to know the performance of the vertical axis rotor to decide how many turns of wire per coil to achieve the desired voltage at the desired rpm. I have no interest in VAWTs because they are inferior in pretty much every way to HAWt turbines, so I cannot be bothered to attempt to work this out for you but you need to know the swept area and the power coefficient and the diameter and the tip speed ratio at which it works best.

cheers

Hugh

is this formula correct for the tip speed ratio

TSR=4π /n

where n is the number of blade.

i see this formula in the internet

thank you 🙂

hi Wil,

In order to do this stuff meaningfully you need to understand what tip speed ratio actually is. It is the ratio between the speed of the wind and the free windspeed around. For a specific machine in operation you can calculate the speed of the blade tips from the diameter and the rpm. I don’t see them in your equation. Or for designing a blade there are other equations.

All of this stuff is clearly explained in my recipe book page 58 and in my more general book Windpower Workshop. You can buy these books or you can take the time to read and understand the theory online. But I am sorry the equation you have above is not going to help you arrive at the tip speed ratio.

best wishes,

Hugh

Hi, my name is Atonye

i’m about to make a 120vac alternator of

20 inches outer diameter

3 phase with 9 coils and 12 neodynium magnets.

Coil thickness=0.8mm

number of turns in each coil with small holes=870 turns

magnet size in inches=2 x 2.5 x .625

connection type=star.

Rpm=1000

I’m hoping to squeeze out about 1,200watts from it.

I’m i on the right path or is there a better and more effective way of doing it?

hi Atonye,

I wonder why you want three phase AC? Mostly we use these alternators to make DC for batteries or for grid tied inverters. You have too many turns per coil. YOu will make 120Vdc at 25 rpm. So you will make thousands of volts at 1000 rpm. If you want to find out how to design an alternator to work at a particular voltage and a particular speed then please start by reading the pages about the subject in my Recipe book and then ask me some questions if there is anything that you can’t understand.

Have fun!

Hugh

What’s the best way to produce a powerful 120vac for home use?

hi

first you need a power source. I would choose hydro power as my first choice if I could find a suitable site. Or use solar or wind power. Charge a battery. Or if you are on the grid you can use a grid tied inverter. It’s not a great idea to produce Ac directly because the amount you produce will not match the amount you want to use at any given instant. So the supply will be unstable.

I hope this helps

Hugh

Hi, assuming i want to do a single phase of 120vac 1200watts can you give me the specs like number of coils, number of turns in each coil, number of magnets, rpm?

hi Atonye,

If you want to get 120V AC single phase direct off the alternator then yes it is possible. But the actual voltage will depend on the load. The open circuit voltage is one thing but when the load comes on the voltage will fall. Another thing you need to consider is the frequency. If you want to have 50 or 60 Hz then you need to use the right number of magnet poles. For example you can make 50 Hz with 2 poles at 3000 rpm, 4 poles at 1500, 6 poles at 1000 rpm etc.

Tell me the speed and the frequency and the number of poles and the power and everything and maybe I can help.

For single phase the number of coils should be the same as the number of magnets.

It’s possible to design an alternator that will give you this output but unless you have a constant load, the voltage will be always changing with the load. The only situation where I can see this working is where you have a hydro turbine or suchlike providing constant input power and then you run a load that is constant or you have a diversion load controller that regulate the voltage but using the excess power that you do not choose to use.

Really hardly anyone does this nowadays. It is much more convenient to use a battery and an inverter if you do not have grid power. The inverter can give you a lot more power than the average produced by the turbine and give it to you when you need it.

I hope this helps.

Hugh

This is what i have in mind to make.

Single phase

9 coils(0.8sq.mm)

rpm=500 to 1000

12 poles from 12 magnets(2×2.5×0.65 inches)

frequency=50hz

power=1200watts

i would be spinning it with a motor with speed of my choice 0 to1000rpm.

Take a look and help me correct any errors in specifications. Thank you for your time.

Should i can make 12 coils since there 12 magnets?

yes you will need to have the same number of coils as magnets if you want single phase output. If the coils do not meet the magnets at the same time you will get different phases.

Also you have to understand about frequency. If you use 12 poles and you want 50Hz then you will have to run at 500rpm. You do not have a choice of speed.

Thanks for quick respond. How many turns of coil would you recommend in each of the 12 coils

Hi Atonye,

It has been a few years since I built a single phase machine and there are also a lot of details about your situation that are unclear to me but I suggest you try 30 turns per coil and connect them in series.

Do not forget that every second coil must be “backwards” because it faces the opposite magnet. so you must connect finish of coil 1 to finish to coil 2 and start of coil 2 to start of coil 3 and so on… If the voltage is too high you can increase the air gap to reduce it.

Have fun and let us know how it works.

Hugh

Thanks for the assistance. I’ll try it out to see how it goes and i’ll let you know the result

Hi

Bear in mind that the alternator will need a fair bit of cooling air blowing over it if you wish to convert 1200 watts. I design for wind turbines that have good cooling but I have no idea what your application is for this.

Hugh

Hi, my alternator is to run a few homes appliances like tv, dvd, fan and ligtings but if i don’t like the way it functions i will just add the diodes and use the dc for powering a universal motor or other dc machines.

I just realised neodyniums are too expensive i’m thinking of trying magnets from tv speakers. They are like cylindrical irons and i wonder if they would perform well if i get 12 of them. How do you think i can use them?