I am about ready to purchase a classic for my wind turbine but I would like some thoughts on my setup first. I have a whisper 200 1 kw wind turbine high voltage model (240 vac nominal, gets up to 300 vac) that is connected to a transformer with a nominal 12v secondary. From there it is rectified with a rectifier I built and fed into two l-16's in series. Control is done with diversion. Everyone talks about the voltage limit of the classic and I cant find anywhere what the minimum voltage is. I want to make sure the classic can work its magic, can it boost voltages down to say 8 volts? Right now the transformer is wye-delta so I could wire it for delta-delta to increase the output voltage a bit. The advantage of this setup is the voltage is so low that I dont need a clipper. I would charge control with diversion much like I am doing now except that I would probably get rid of the tristars and use the classic's aux options to control a SSR as the tristars make a racket. Any thoughts/concerns with this setup?
....Ive been reading some other threads and is it correct that the classic can only buck not boost? assumed it could boost hence my question about working with voltages below batt....
That is correct the Classic will need battery voltage or higher in order to charge.
Ok that certainly clears things up. I should "change gears" on the transformer to delta-wye then which should give me plenty of overhead but still have no possibility of exceeding 150v
Quote from: electrofelon on December 13, 2011, 01:25:51 PM
Ok that certainly clears things up. I should "change gears" on the transformer to delta-wye then which should give me plenty of overhead but still have no possibility of exceeding 150v
The problem with assuming your turbine will not go above some certain voltage is that people don't take high speed wind gusts into account.
We have talked with SEVERAL customers that did not think their turbine would go above a certain open circuit voltage and it ended up going very high.
If you have good wind, you are going to have high speed gusts. The only kind of turbines we have seen that have a chance of not going above a certain voltage are usually variable pitch machines. A "Clipper" will also ensure that the voltage doesn't exceed a voltage limit.
The reasons that these controllers don't boost is that for one, it makes the controller a bit more complicated (and expensive) and if you pick the right number of turns (or turns ratio in your case), 99% of the power will be above the battery voltage anyway.
At low wind speeds, which produce lower voltages, there just isn't much power down there and not worth trying to harvest.
That's my take on it anyway.
That being said, the Classic will take higher than 150V input (for a Classic 150) but it won't operate above 150V input. If you have a 48V battery, the Classic 150 can safely take up to 198 Volts input. BUT, I would not count on the turbine NOT going above that voltage because of gusts. What if you get a 100 MPH gust ?? What voltage will it put out ? A Clipper will help keep that voltage and the turbine's RPMs down to safe levels.
boB
PS... I have attached a picture of about one (1) minute free-running DC voltage output of a small(ish) turbine at my house. Notice how it looks kind of like random noise. The reason that the down-going voltage is slower than the rising voltage time is because the Classic input capacitors take time to discharge. Remember, the Classic MPPT mode is "OFF" in this sample capture. In reality, the highest voltage here is about 100 Volts and somewhere around 35 MPH maximum as I remember. The average wind speed for this one minute capture would be approximately the average of this voltage waveform but I haven't calculated it. As you can see, the wind varies a LOT.
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boB,
I am fairly certain that in my case the classic would be ok, but the turbine may not. The turbine makes .5 volts/rpm unloaded. I read that the max rpm is 1100 which is really screaming for a 10 footer but yeah I guess it could get up to whatever it would take for the blades to explode. Say it gets up to 2000 rpm, completely unloaded that would be 1000 volts. If I did "middle gear" on the transformer-delta-delta, that would divide the voltage by 12 which is 83 vac. Multiply that by 1.35 for rectification and i get 112vdc. I think i would damage the wind turbine either by damaging the insulation on the windings or the blades would fail before damaging the classic. Either way I certainly would not want it to get going that fast. When in wind mode, what situations would cause the classic to unload the wind turbine? What does the classic do when the batteries are charged?
The Classic quits putting current into the batteries when they are fully charged. Yes, this unloads the turbine. You really need the Clipper with this turbine. You will be able to do three stage charging with our Clipper. We have shipped a dozen Clippers now. More metalwork has been ordered, so it won't be long until the Clipper is in stock.
Quote from: electrofelon on December 13, 2011, 06:29:37 PM
boB,
I am fairly certain that in my case the classic would be ok, but the turbine may not. The turbine makes .5 volts/rpm unloaded. I read that the max rpm is 1100 which is really screaming for a 10 footer but yeah I guess it could get up to whatever it would take for the blades to explode. Say it gets up to 2000 rpm, completely unloaded that would be 1000 volts. If I did "middle gear" on the transformer-delta-delta, that would divide the voltage by 12 which is 83 vac. Multiply that by 1.35 for rectification and i get 112vdc. I think i would damage the wind turbine either by damaging the insulation on the windings or the blades would fail before damaging the classic. Either way I certainly would not want it to get going that fast. When in wind mode, what situations would cause the classic to unload the wind turbine? What does the classic do when the batteries are charged?
Transforming down the voltage can definitely help of course.
The Classic will unload the turbine when the batteries are full and the wind is blowing good and it will also tend to unload the turbine when it reaches current limit on its output side.
boB