AC is really DC

[artv]

I think there is a mojor design flaw...............the only reason for AC is what??/   Current flows when you pass a conductive material through a mqgnetic fielld.Current flows in a contiuos direction in the coils of a set situation of magnetic fieldThen you alter it by reversing magnetic polaritys.Thus ccreating AC...Then change it back to DC.............This just does not make sense to me???                    wasting lots of energy chaning stuff

[bob g]

you have some choices to make, you either mechanically rectify the ac or do it with diodes

no other way to do it, however

that is not the only issue, all generators produce AC power, and you can design to make only positive pulses, but
after each pulse their will be a period where the collapsing field will go hard negative, in the process you end up with
some really harsh and crude AC power which is hard to work with, inefficient to transform (causes heating) and you still
have to rectifiy it to get DC

its just a fact of life, might as well accept it

as far as being inefficient?  there is nothing more efficient than the production of 3phase sinewave AC current, you can effectively
and efficiently transform it without making lots of heat, and you can rectify it efficiently without fear of blowing diodes.

very good alternators, that are quite large can be well up into the upper 90's in efficiency, even a properly applied automotive alternator
can reach 80% even after factoring in rectifier losses and excitation current.

perhaps you will be the one that rewrites the physical laws that dictate the production of power from a generator or alternator, but
you will have to excuse me if i withhold my money and bet against you.

bob g

[Flux]

No it doesn't make sense but you are stuck with it. The only machines that can generate dc directly are homopolar things based on Faraday's disc and these have never achieved any real commercial success.

Before the days of silicon diodes the ac was converted to dc by a mechanical switch, this is the commutator of a dc machine. The fact that the terminal volts is dc doesn't affect the fact that the emf in the coils is still ac. There is not a lot of difference in efficiency between a commutator and silicon diodes but above a few volts the diodes are much more convenient and are maintenance free and this is a big factor for wind power.

You have to give up this misconception that you are going to produce dc direct, it hasn't been done effectively yet and many of the world's best brains haven't had much luck. Carry on if you want but I doubt that you will crack it.

Flux

[artv]

Thanks bob g,Flux....I'm not trying to rewrite any laws of physics,and I figure these machines designed the way they are ,are close to 100% efficient because it costs nothing for the wind,after a given amount of electricity is produced this pays for the materials used to construct the generator."Some of the best brains"I believe two of them just responded to my  question.As for Dc that is what these machines produce ,alternated by magnet orientation,reversing the dc flow every 30 degrees of rotation, this is the Ac output(in the 12 mag - 9 coil design).This is where I think there could be room for improvement and I'll keep the questions coming....I have thousands of them...We need people like you guys to figure this out ....there's always a room for improvement until you hit 100% thats as far as it can go.I hope people with your know how continue to look for better ways ,not just accept the way it is as the best........artv.........100% just a dream.....but 98, 99 maybe

[bob g]

Art:

there is nothing wrong with questions, as far as i am concerned, however i would like to make a few points

the aircore axial alternator as outlined here is about as well refined as anyone is likely to make it, i have no idea
what its actual efficiency is, but i doubt it is anywhere near 90% and quite frankly is it really important?

btw, Flux has forgotten more "yesterday" than i have been able to amass into my hard head over the last 40 odd years.

if it were me i would accept without proof anything he says as if it were chiseled on the back side of the stone tablets that were
brought down from the mountain by moses.  i am not saying Flux is older than dirt, just that he has an enormous amount of
experience and knowledge for folks like you and me to draw from.

now having said all that, it is my opinion that if you want to make a serious contribution to the improvement of efficiency of one
of these alternators used in wind power, then work out a reliable MPPT or some sort of converter that would allow the rotor
to run at a fairly efficient speed and match the alternator to the load.  which also btw our friend Flux is a big supporter of iirc.

in my mind such a system would allow the alternator to run at a speed high enough, with voltage much higher than battery voltage
and then down convert to the battery at a voltage needed to charge properly. the end result would likely show very significant increases
in efficiency.

getting some increases in efficiency would be far easier with that sort of thing than it will be to try and build a better alternator to start with.

ymmv

bob g

[12AX7]

kinda like the way cheap stereo's hurts my ears,   the title here hurts my eyes.

Can't be talking about the group AC/DC.

ax7

[artv]

bob g I agree that Flux seems to be the most knowledgable person on this site....me personally know nothing when it comes to these turbines I just know what I read and interpret I'm sure I'm way off lots of times ......thats the reason for the questions.I'm not trying to change things just trying to understand how they work ,I don't even know what MPPT is, btw is, or iirc To be quite honest I'm almost 100% computer illiterate it takes me 20 minutes just to type this......luckily for you guys or the questions would be a mile long..........again thanks for the replies I appreciate it very much.....artv

[artv]

Ax7 is it not true that current flows in one direction in a coil then reverses when you reverse the polarity of the rotor mags.

[wpowokal]

artv you seem just the guy to improve on the following, imagine if you will a duel rotor design but on one rotor all north facing magnets and the other south, the stator consists of two rings of wire, one small placed inside the magnet's diameter the other a larger outside. Now the conductors radiate between these two, a DC machine? 

[12AX7]

artv

I'm sure the answer to your question is yes.
But it has little to do with the title of this thread.

Tell me,  isn't it true that  .0000000000001 hz is still AC?
A voltage that "swings" past true ZERO (from either the positive or negative region) into the opposite region is AC.

Any voltage that swings + or - but never crosses ZERO is a varying DC voltage.   
anyhow,  it's just the title of this thread that causes a ripple to run up and down my spine.  *L*

what ever, have fun

ax7

[rossw]

I think there is a mojor design flaw...............the only reason for AC is what??.............This just does not make sense to me???                    wasting lots of energy chaning stuff

One thing that nobody has mentioned here, but may not have been immediately obvious is the safety aspect.

At low voltages (12V, 24V) there's not much difference I guess, but at higher voltages (and it becomes really apparant once you get over about 60V) is that it's VERY easy to strike an arc - and in most modern switches with (fairly) small contact spacing, it's very HARD if not impossible to quench that arc.

AC, which passes through 0V 100 or 120 times a second (50Hz down here, 60Hz in many countries), arcs are virtually self-quenching.

An arc at 100V and as little as 5 orr 6 amps (it's trivial to get this sort of power from just a few PV modules) - makes a LOT of heat. Switches, breakers, fuses, junction boxes, screw terminals - anywhere you manage to get an arc started, will get VERY hot VERY quickly.

[Flux]

Yes this is a bit off topic ( if the subject was ever on topic in the first place) but indeed dc does present significant problems.Iin the old days when high voltage dc was common we had QMB switches for lighting and for higher power we had elaborate breakers with blow out coils and arc chutes. Anyone dealing with higher voltage dc systems nowadays will find such things near impossible to get and very costly ( they always were and we soon changed when dc became less common).

It is in fact quite possible to get serious arcs from fairly low powered high voltage panels. Arcs from high power high voltage dc sources can be a big issue.

Flux

[artv]

Wpowokal ...........would this work like kind of a step -up transformer??.......I appreciate your reply....artv