using ceramic mags

[Bruce S]

All;

I'm putting this question in the R & O area since I am asking for opinons.

This will be my first real question in the wind forum before I start getting serious about building a wind gen of anyy kind

First of all, since I do live in the city I do not and by current city law cannot rely on a good 17' wind generator.

I will more than likely put up a Lawn 'mill so the city doesn't come knocking on my door "again".

My main question here could also be for others who are just starting to get into building and need hands-on time.

Also, with due respect to how strong the Neo(s) are I can understand why it would be good to go this route.

However, there still seems to be a lot of good uses for the Ceramics, Jerry is currently working with them and since I have upwards of 150 of them, I was wondering if the people that have seen and built Alternators using both Neos and Ceramics would think that it would be a valid point for hands-on experience of using the Ceramics. the ones I have measure 49mmX23mmX11mm.

I know that using Neos would be the best route going if I needed to make something that I needed to depend on for years to come and needed one that would put out 100s of watts once properly thought out, i.e. wire , number of coils, number of turns in those coils for a given wind range and so on.

I'm not looking to put AmerenUE out of biz, but to get into the 10 watt size, something I can get away with, and make use of the Mags on hand.

I do plan on using repurposed wire ( i.e. degaussing coils) so even if I don't make 1 watt in a 20kph wind it's the building and numbers crunching that is the exercise, alomg with taking what others deem of little worth and making it useful.

Before it's asked , yes I've read the FAQs the old forum and can almost do the math on one sheet of paper.

Thoughts?

Bruce S

 

[Jerry]

Hi Bruce S.

I'm planing on a 4ft. Would that be acceptable with your city fathers?

I'm hoping that the high turns count, high magnet count, large diameter (12" disc), iron powder in the coil center will extract a small amount of power at 5 mph? Maybe 5 watts or so?

                            JK TAS Jerry

[scoraigwind]

I have used both and on the whole my impression is that ceramic magnets will last a lot longer than neo magnets in the real world.  Neos seem to suffer all sorts of unexpected corrosion problems whereas ceramic magnets are more or less indestructible.

Ferrite/ceramic magnets are very weak compared to neos but they are cheap and you do not have the stalling problems with ceramics.  The efficiency of the alternator is lower but it is also larger and more capable of dissipating waste heat.  And a less efficient alternator is often better matched to the blades for speed and power.

ON the downside you would need a pretty big ceramic magnet alternator to get a decent short circuit brake.

As for lawn windmills, whatever turns you on - but I recommend you get into solar water heating instead and get some more useful result.

[Flux]

I think Hugh has summed it up pretty well. This corrosion issue with neo is something that bothers me but may not be an issue in more modest climates.

For small machines ceramics work well enough but you need a lot of them and the alternator relatively will be very large. It will probably not be possible to burn it out if you build it sensibly, the power density is too low.

I don't think it is worth trying tiny awkward shape ceramics from scrap equipment but the size you have will work for a small machine. If you have at least 24 of them then you may manage a small mill with 12 poles. You should be able to use a stator about 1/2" thick and you will be using many more turns than for neo so the resistance will be relatively high so it will need to run faster in high winds even if you keep the same cut in speed.

Probably up to about 6ft ceramics are reasonably practical beyond that size you need to consider iron cores if you don't want to end up with a monster.

I have done very little with ceramics, for larger sizes I managed better performance from wound field machines before neo became available. I did build one or two ceramic machines based on cut large speaker rings and they worked well enough for use on boats.

The one I built with magnets slightly smaller than yours had 16 poles with a 5ft prop. It also worked ok but I used a series parallel change over on that one. It is still operating in a different form with 3ft pvc blades charging an electric fence as far as I know.

Flux

[hvirtane]

There are quite many examples on this board, how to build an axial flux generator using microwave magnets.

A very good book by Alfred Forbes, 'Homebuilt Dynamo' shows another kind of design and all the calculations, what you can do with ceramic magnets.  

Forbes' design is in principle similar as the one in the following picture.

With that kind of design dissipating the heat shouldn't be a big problem.

- Hannu

[zeusmorg]

 Since you are building out of materials on hand, i see no reason not to proceed. You probably realize that the available flux will keep the output of a ceramic magnet machine much lower than one built with neos.

 What I would do, with those size magnets is if I were building an axial flux alternator would be stack them in a configuration of 4, 2 deep and 2 long. This will increase your flux somewhat. Keeping your air gap as low as possible will also increase the efficiency. You may also consider building a multiple stator machine.

 One trick that was used in the days before neos was to add ceramic magnets to an excited field coil, the magnets provide the necessary excitation for startup thereby eliminating the need for a battery powered field coil. Doing this would also be possible. Then the field coil current was "matched" to the available wind.

 I suppose my decision to use the ceramics would be based on what else I had to purchase to build the machine. There are just some designs that make no sense from a financial standpoint, so I ask myself is this design worth it over what I would have to spend to build a better design?

 As fas as mixing neos with ceramics, once again it would depend on what was on hand. I could envision increasing the flux density of ceramic magnets with neos, for instance.  

[electrondady1]

if you live in the city bruce,

 please consider a vertical axis mill.

the rotor dia. can be whatever you want .

and you could make up for a reduced flux density with a high pole count.

[Norm]

Hiker seems to have pretty good luck using

ceramic magnets in conversion motors....

[Bruce S]

All;

   Want to say thanks for the great input.

I'll try and answer them in one post so as to keep the lines easier to follow.

Jerry , I'm thinking that since I can get away with a 24" blades at first since they come with the HF lawn ornament; then sneak upto a 48" set. I'll of course have them painted pretty so the "city fathers" do get ticked.

Your recent posts are some of the reasons I went back to these. The L.O. is a multiblade that looks pretty, but since I'm not moving water, the new blades will total 3. It's the tower I'm after.

Hugh: I have to say your book as become the defacto when speaking about windmillsse things in the neighbor-hood circles and I'm waiting for Santa to order/bring me the Dan(s) book as well :-)

Solar heat: doing that already; starting with the original designs for Mother Earth and Builditsolar, I have learned and built some nice small units that even when it's only 16F outside , if the sun is shining we have heat going into our basement, which is the last place left untouched. I can with personal tests and a couple cheapo meter  that came with temp probes, the bubble wrap with the bubbles towards the window glass works better than flat side on the glass.

My biggest problem was the most recent power outage the city had and my ablity to turn on lights and make coffee while everyone else couldn't :-)

Got bit by the bug since then.

Flux: Many thanks too. I will keep your idea of wound field in mind, I believe that the electric weed trimmers use this type of motor, I have a few, and while digging into an older AC powered lawn mower it seems that it is in reality a DC unit using nothing more than a recitifier.

St.Louis' climate is sometimes called the land of the 5th season, don't like it, wait 30mins and it'll change. Yesterday it never got higher than 30F today 55F with freezing rain this evening, so the corrosion will play a factor.

I know by trying different math inputs the mill will need to be a fast one to say the least, so I'm not going to try for the low speed winds that prevail here, but will try and set it up for speeds in the 10+mph area.

Hvirtane:

Interesting too, I will find the book and give it a very close read. The multi-lam setup may be just a little more than I want to try on this first attempt. Purchasing stuff is like everyone else's the more re-purposed stuff the better :-)

I have been keeping the degussing coils  from the back of large monitors and old TVs the wire seems to range from 20 ga to 18 ga. I'm still reading on the multiple windings in hand. Easy enough to read and do once I get to the point of winding and design.

zeusmorg:

I am going down the path of stacking. I would use HD mags along with the ceramics, but more than likely on the next go around.

electrondaddy1:

VAWTs to me can be beautiful. Our Botanical Gardens has 5 of them, they are non power units but are so pretty, I think I could get a city waiver, but they look nothing like anything currectly here. I did one time put up a pic of one.

One of the designs I am looking very closly at is Windtstuff Eds little 50watter , I know that even if I build this unit, the output of say 5 watts could be possible and easier to hide :-)

So YES I will keep VAWTs in mind. My daughter built -Eds trainer and it still works, no matter the amount of wind it takes it still just works.

Which ever unit I build first will be multi-phase. I hope to be able to have it wires so I can try different connections for testing, "D" "Y" & "J" along with wave winding.

Norm;

I did look at those, spent lots of time reading and doing the numbers, but I think I'm going blood & guts on this one for a full build.

Thanks Again;

more reading to do then will begin posting my decissions and builds.

Cheers

Bruce S

 

[Norm]

You should have got my E-Mail by now about the

34 inch one I hooked to the RT stepper and right

away when you start building these you realize

for a small mill you a small dual rotor (no cogging) alternator is what is needed for low winds....the cogging part is the biggest issue

that I have but I just can't pass up using the

little steppers they are such neat little power

houses ....in my opinion  just getting past that

infernal cogging....however it is a challenge

and I truly enjoy it .....schemes of centrifugal

clutch (not as difficult as you might imagine)

yo yo's have them ( a reverse clutch?)