AXIAL FLUX OR PMA

[Yianie123.]

i am new at wind turbine so any advice will be greatly appreciated.  I have seen a lot of internet sites selling PMA made from alternators and there supposed to be the best.  And now I see a lot of talk for axial flux wind turbine that people make.  Can anyone tell me which is better and for what reasons?/

[artv]

You can stop looking ......This is the best site you'll find ..........whether you want to"do it yourself "...or let" somebody else do it".............this is the place to be........artv

[willib]

An axial flux can be tailored to suit your needs.

Whether it is for wind or water you have more options with a axial flux machine.
You can choose its voltage ,12V to 48 Volts or higher.

If you are building one for water power you can build it directly for the output of your water turbine.

If it is for wind , you have a harder choice to make. Because of the unpredictability of the wind.

But you still have the choice to make it whatever voltage suits your needs.

[wpowokal]

I have both and believe both have their own virtues, sites selling PMA's are possibly flogging tape drive motors which are generally unsatisfactory.

As Willib said the axial flux is very much a roll you own option.

Three phase motor conversions also have flexibility, you can choose 2,4,8 pole motors which will suit different voltages and blade diameter, for my money they are more robust if you use an industrial motor, good bearing and shaft size, are fully enclosed and somewhat self limiting in output.

With either option you build your blades to suit the alternator and your wind conditions, it somewhat depends on your conditions and skills.

allan 

[tecker]

You can pick a motor that fit's your needs so there's really not a reason to shy away from a pma . For the most part thought you begin with a very robust machine from the start when making an air core . Large magnetic field thick wire just a good load handler . These guys that hammered out the Axle did all the F)(*&)(*ups and have prepared a manual for battery chargers . The Air cores really haven't addressed on grid living . And that's not an issue . :They love being in the sticks as I do and off grid .  The UL approved devices will have their day in the form of an inverter/ interface that is universal in design to use What's extra or on hand . So make some of both and enjoy the ride.

[TomW]

Yianne;

Fixed your title spelling of "Axial" so it will show up in searches later.

Tom

[frepdx]

i am new at wind turbine so any advice will be greatly appreciated.  I have seen a lot of internet sites selling PMA made from alternators and there supposed to be the best.  And now I see a lot of talk for axial flux wind turbine that people make.  Can anyone tell me which is better and for what reasons?/

Not many people have the capability to fabricate electrical steel cores. So if you enjoy fabricating and want to make your own alternator, an air core is the way to go. There are several 'cookbooks' for axial flux air core designs that are efficient, robust and tailored for wind power generation.

[Ungrounded Lightning Rod]

i am new at wind turbine so any advice will be greatly appreciated.  I have seen a lot of internet sites selling PMA made from alternators and there supposed to be the best.  And now I see a lot of talk for axial flux wind turbine that people make.  Can anyone tell me which is better and for what reasons?/

By "made from alternators" I assume you mean made from automotive alternators.  Right?

Automotive alternator conversions for wind have issues with high RPM requirements and bearing life.  We tend to avoid them here for those reasons.

Typically we build permanent magnet alternators of either coreless axial flux from-scratch designs or radial flux induction motor conversions.  Both can be easily built for the RPM, torque, and power output requirements for wind machines of a range of sizes appropriate for home or small business use.

The coreless designs have the upside that they're easy to build, don't require much special tooling, and don't have critical tolerances.  For wind they have the particular advantage that they have no "cogging", so when the wind rises from a calm they don't tend to hold a mill stopped until the wind speed is above that which would drive the mill, if it were spinning, to cutin, missing out on some power (which is particularly precious during relatively calm periods).  Their main downside is that they have difficulty losing heat, so automatic furling to avoid overheating and burnout is necessary and its adjustment is important.

Motor conversions are heavier and require more tooling.  They tend to cog if the magnet layout is not done properly, but keeping the cogging down to a level where the break-free wind speed is below the cutin wind speed isn't too difficult.  They're strong and cool very well, so it's a lot harder to burn them out.

For small machines some of us use generators-of-opportunity.  Typically this means a permanent-magnet DC motor (such a tape-drive or other servo motor) or stripping the electronics off a permanent-magnet electronically-controlled AC motor (such as those found in washing machines (i.e. F&P) or furnaces (i.e. GE)).

[Rover]

I've never built or used and Axial flux , mine (and all the atempts) are either ECM conversions, treadmill motors or other convertible iron core type motors. Someday I may build an Axial flux, but I'd have to move first.

For me, the cheapest way to get in (this is a hobby) was using   some motor cast away, and it taught me a whole bunch .. 1) I live in crappy wind area (just my house) 2) There is no guarantee from a conversion or re-tasked cast away.. they all be different. 3)Typically, a good axial flux will out perform a conversoin , re-tasked  cast away, and be much cheaper than commercial unit of the same wattage (from reading here.. no personal experience.. but if you compare watt to watt....hmmm).

If I had decent or better wind, I'd spend the time /efforrt for an axial. Why? based on everything I've read on here, when you get into to bigger units (blade diameter) it is a whole bunch cheaper.

A lot depends on your situation, mechanical, electrical and so forth skills

[97fishmt]

An ac permanent magnet servo motor works well for me!
Very cheep (if you can get a good deal) 3phase so you can brake
and sealed from the elements.  A done deal.

[scoraigwind]

Axial flux alternators with air core coils are not jsut easier to build, they have no magnetic drag so they start more easily.  Another big advantage is that the output current is not limited like it is with motor conversions and car alternators.  So you can brake them in high winds and you can get high power without overspeed.

PMA means permanent magnet alternator, which can be of any type (axial, radial, ferrite, neo, etc).  But the ones with coils mounted in laminated cores of steel (old motors and car alternators) have a limited maximum current and if you push them harder they just run faster and faster instead of producing more power.  This is nice in the respect that they do not burn out but it means you can't brake them and the blades tend to overspeed in stronger winds.

Yes axial flux alternators do have issues with burning out if pushed too hard and you do have to ge the furling right, but it's a great comfort that you can stop them any time and it's nice to see them start up freely in the lightest of winds.  Plus it is nice to be able to build them from scratch in any size you like.