Looks like I had a LOT of thoughts.
"taking the specifics of my 24 v"...
Sorry, those numbers do not make any sense to me.
Guessing they came from a sales brochure.
The voltage is capped by the battery.
As the RPM climbs, the amps increase.
The battery voltage, amps, and losses sort of control the RPM to some extent (which is why an unloaded windmill goes so much faster).
You understand shorting it to a stop. That is 0V output.
Using a 24V as a 12V is basically running it 'half shorted'.
"with new blades voltage remained low (about 15V) but sounded like a lot
of power going into the battery."
That is the sound of stall.
Uh... like the blades are not smoothly and efficiently interacting with the wind... the wind is whistling around them???
Might have a look at this guys experience, with special notice of comment #4 "SSSSSSSS".
He details some symptoms in the earlier posts he linked to.http://www.fieldlines.com/story/2009/11/30/194624/37
Side note: Overspeeding blades tend to make a "ZZZZZZZ" sound. LOL
After you have heard both a few times, it is fairly easy to tell the difference. Honest.
I have no idea how that GTI is designed.
Best guess is the wide input voltage range allows it to peak at 600W output.
When the input voltage is 55V, output is 600W, input is 660W...
Now the fun part. :twisted:
Your PMA numbers are a bit deceptive.
See my comment here:viewtopic.php?f=32&t=3124
Take that Presto Crap thing for example. It can only make 7A at 1400RPM.
(after 1400RPM the amps actually go DOWN which I did not notice before)
So their 1683W windmill has 0% chance of overloading your 600W inverter.
Yours, at 490RPM, with 0A of output, the open V is only 33.6V.
Pull 12A out at 490RPM, and the voltage will drop like a rock. So will the watts. So will the amps, after the voltage drops. Many seem to be self balancing.
I do not intend to imply your PMA is junk, but all iron core PMSa will exhibit the same characteristics to some extent.
Most of the no-name unapproved Chinese GTIs limit the input amps. Maybe yours is limited to 12A.
When it reaches 12A, it does not allow more amps in. This allows the PMA to run at a higher voltage.
Reasonable chance your PMA would need to operate at 12A and 55V (at the SAME TIME) to overload the inverter. Reasonable chance your PMA can't do that.
The problem will be if the grid goes down.
The inverter has no load. The windmill has no load. The windmill has no load so the blades spin a lot faster. The windmill's Vopen goes up fast, maybe exceeds 55V and smokes the inverter.
It would be much easier to make some kind of snubber circuit to hold the volts down.
A frequency switch is Rube Goldberg at a minimum, and a bad idea at the worst. Who cares how fast it is going???
Shut it down at 55V, which is about 800RPM? Which should happen at about 3X the cut in or 18MPH. Seems self defeating.
Need to control the voltage. I made a few for larger windmills of the 17' class. Overvoltage conditions triggered a relay to shut the windmill down until manually reset. Fairly simple. They work well.
Might google Roger Stafford or Dan Lenox.
If this is a no battery system, there are simpler ways to do it. I prefer not to publish them publicly.
Email me if you want a sketch.
10,000 ways to skin a cat.
Shawn and Chris,
Limiting the input voltage using batteries is going to be a very bad idea. Especially if the grid goes down.
If the grid goes down, the batteries can go to a very high voltage in seconds.
If the battery is 48V, the GTI will run them down to like 5V each.
If the battery is 24V, then the inverter input voltage will be clamped to the battery voltage possibly limiting the output to less than half what it could be.
Naturally, that is related to non battery based GTIs. Most are somewhat based on loose MPPT algorithms which will be comprimized doing silly things the designers did not intend.
Might have a look at Mertz's GTI endeavors. That Chinese thing he is using is intended for a 12V battery bank. The retailers obviously have no clue how to use it and distribute very faulty info.
But the inverter's design is pretty good.
Wish they'd get it UL Listed. I'd buy one (or more).
Blisters on all both my typing fingers...