The synchronous impedance will be all the things, that bundled up together will work to stymie our attempts to get the output we want, from the thing we have got to use for the purpose.
If we use an axial flux, with big magnets, then essentially it is just a resistance game to find your upper limit.... ie how much power can the stator shed in the form of heat to stop it deteriorating.
The next problem we encounter is the inductive reactance, which is a linear function. It is simply the impedance that the inductive characteristics of the stator winding presents to current flow, and is dependent on the stator inductance and frequency. If we know the inductance, and the frequency we are interested in, we know the impedance it will present to the current flow.
The next one is not commonly discussed in windmill forums like these. Possibly because we deal mostly with axial flux designs, which by their construction push this problem to the bottom of the heap..... it's this pesky reactance we speak of when we talk of iron core machines.
With all endeavors in generating electricity from rotating machines, we need flux linkage........ this means we need to get our operating flux to penetrate the coils in order to generate an EMF..... simple enough. we wave a magnet past a wire and get EMF. Thats cool, but we also know that if current flows through a wire (the general idea here), it will exhibit a magnetic field of it's own making. It will be in opposition to the magnetizing force we used in the first place.
This sets up a problem. We need all the flux from the magnetizing field (magnets) to penetrate the coils for us to get the maximum benefit, but we have opposing fields trying to stop us. The net result is that we cause some of the incoming flux, to NOT link the coils, and find some other more amenable flux path, which does not benefit our generator..... ie we lose some of our flux to some other flux path.
This problem was caused by current flow in the stator coils, so the more current we cause to flow in the coils, the more interference with the magnetizing field we cause.... we can see where this leads, in the extreme, the current flowing in the stator presents enough megnetomotive force (MMF) in opposition to the magnetizing MMF, that we get a stalemate at some point. We see this point when we short a mill, to stop it, only to find it runs away instead.... amp turns.. not watts. It runs away because we are no longer linking all the flux through all the turns. Use less flux, need less torque..... mill runs away...........
With axial flux, the magnets are very strong, and the air gap very big, and no core to focus the field, so it is much harder for the back MMF to influence the magnetizing field... so we see these alternators as resistance limited (how much heat can you get rid of). The inductive reactance is of little consequence as the inductance of the air coils is very small, and so the frequencies needed to cause significant impedance are not practical considerations, and the armature reactance is similarly muted.
With iron cored things, we get more problems from the inductive reactance and the armature reactance.
Because we are using iron, we can use less magnet, and use small airgaps. Smaller magnetizing force channeled better through iron core stators, allow for better performance with less magnet.
Nothing is for nothing, and so we find that the inductance of the stator coils will be bigger, so the effects of inductive reactance will be more pronounced, and can indeed control things at high enough frequencies.... and the armature reactance becomes a capitol problem.
With less magnetizing force, and tight air gap, and a core to focus the back MMF against the magnetizing MMF, we are set for a true showdown.
It comes down to Ampere Turns.. You can use more turns at less amps, or more amps at less turns. It will produce the same magnetizing MMF, and current limiting will set in.
This overrides the resistance limit of the stator in some cases, and salient pole machines with long fingers and ferrite magnets, can run short circuit all day without over heating. The AWP can too.
BUT
If your going to generate such high power, you must be going to put it somewhere. The battery bank would be huge. I'm guessing grid feed??
If so, perhaps just use a big three phase induction motor, and drive the grid direct. (see breezy site for ideas). Your already building the gear box, maybe this could solve the generator problem simply too.
We have a 35 foot induction generator here, and it works particularly well, and has done so for over 25 years. Direct connect to the grid. No pitch control so big direct brakes are necessary. We dont use a motorbrake (like breezy), but brake the prop directly. It does have tip flaps.... I love em.
..................oztules
Must go will edit later perhaps
