The Axial Flux in this very descriptive http://www.windstuffnow.com/turbine%20kit.pdf has 12 magnet pairs for 6 pole changes per turn, It puts out 3 phase current from 3 coil sets of 3 each (9 coils) It has problem that some consider a solution, namely to minimum startup wind speed, it doesn't use cores in the coils to better close the magnetic circuits... The result is that the maximum achievable magnetic flux is limited by the width of the air gap... No professional made motor or generator allows itself such a 'fo pa'! We recently started this group http://tech.groups.yahoo.com/group/Performance_Axial_Flux/ to develop functional improved Axial Flux Motors and Alternators! We know that cogging as produced by only 3 phases closing magnetic circuits over the paramagnetic cores of only 3 phases is an enemy to low wind speed wind generator startup... So we use more phases and even more cores, look at the design on the groups homepage 9 Phases 18 coils 36 cores, its cogging should be minimal! We are getting higher voltages per winding because of larger delta Flux, and we have the option to rectify the phases in series or in parallel to adapt to a wide range of required output voltages! We are still looking for people that can help making a spreadsheet that allows even beginners to select configurations and windings depending on magnets used RPM and air-gaps etc... Greetings Tobias Gogolin founding member of Performance_Axial_Flux On Wed, May 21, 2008 at 1:06 PM, Detrick Merz wrote: > The [permanent magnet axial flux] alternators displayed at > otherpower.com (and a few other places) are intended to satisfy a few > requirements: > > - easy/inexpensive to build/acquire > - high output at low rpm > - self-starting output > > They seem to primarily be directly coupled to things that turn at low > speed... wind turbines, slow-speed diesel engines, (exercise) > bicycles. Automotive alternators tend to fall short in the second and > third category. They like to turn at high RPM (~10k or so), and they > require their field windings to be excited before they produce output. > > Sure, you could build some type of gear/pulley assembly to mate your > driver's RPM (windmill blades, slow diesel, pedal power) to your > automotive alternator's design RPM, but then you have losses in the > drive train. These folks would rather have something that's dead > simple, works, and is easily repaired if problems arise. To solve the > inefficiencies created by an arguably poorly engineered design, they > throw extra magnetic flux into the mix. It's an easy solution, and > seems to work well enough. Then they use some rectifiers and > off-the-shelf inverters to clean up the output... not much different > than how most portable generators produce (somewhat) clean AC these > days. I suspect there's quite a bit of satisfaction in having "built" > the thing with your own hands from scratch, too. The automotive > alternator would be too easy from that angle :) > > Being hand wound, these things are also fairly easily adjusted for > other voltage outputs... 24v and 48v designs seem popular too, for > feeding the larger inverters, and reducing line losses. There's also > a bit of safety factor with them... tie all of the outputs together > and the things pretty well lock up... helps to provide some additional > safety factor if you're performing maintenance on a wind turbine, or > if you need to have the thing shut down in high wind. I don't believe > you easily get those benefits with an automotive alternator. > > On Wed, May 21, 2008 at 3:42 PM, Herbert Graf > wrote: > > On Wed, 2008-05-21 at 13:30 -0600, Cedric Chang wrote: > >> Sorry if this has been asked. Are these alternators more effective > >> than an automobile alternator ? > >> cc > > > > I was wondering the same thing. > > > > The typical automotive alternator pumps out around 50amps at 12V, pretty > > close to the 500W mentioned. > > > > Heavier models can pump out 100amps or more. > > > > Obviously they are not optimized for size/weight, and they also drop off > > in output quite a bit at lower speeds. > > > > TTYL > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- Tobias Gogolin Tel. Movistar (646) 124 32 82 Tel. Telcel (646) 160 58 99 skype: moontogo messenger: usertogo@hotmail.com You develop an open source motor controller at http://groups.yahoo.com/group/GoBox and an open source electric motor/alternator at http://groups.yahoo.com/group/Performance_Axial_Flux -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist