Project Journals > Chris Olson
180 volt 3.2 meter turbine
ChrisOlson:
This is the stator for a new turbine I'm going to experiment with - just got the stator done today:
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This new turbine is a 3.2 meter machine like the last one, with a geared generator. But I'm using a 12 pole 9 coil three phase neo generator on it. It will hit 180 open volts @ 450 rpm (blade speed), and it's design max power @ 400 rpm is 160 open/147 loaded @ .47 ohm internal resistance for 27 amps, or 3.9 kW power output @ 91.9% power efficiency at the generator.
It will require a lower gear ratio than my previous ferrite generator, which will improve the drivetrain efficiency by about .6%.
The purpose of this experiment is to see if I can build a CHP turbine. Run the Classic 150 controller right up against its voltage limit with the blades running at TSR 6.5 so the voltage clipper will be required to come on just to regulate the voltage during normal operation. Then dump the excess to three phase water heating with the clipper as part of normal operating parameters.
The reason I chose a neo gen for this one is because it's hard to get that sort of efficiency and voltage from a ferrite generator for a turbine this size. With the neo gen it's easy. I had to de-rate my ferrite 3.2 meter because it wouldn't furl running at too high of a rotor speed. With this one I won't need to over-speed it to get the voltage I want from it to be able to do this, and at 30 mph those 3.2 meter blades got 4.1 kW available at the shaft.
Rather than de-tuning it, I want to build one that can run balls out just to see how much you can really get from a 10.5 foot turbine. :)
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Chris
rossw:
Chris - serious question.
If you're building turbines that can run balls-out all day and not explode or catch fire, have you considered doing away with the furling tail and all its attendant complexity, cost and weight, and making downwind units?
For a modest increase in weight/complexity/cost, you could put a disc brake on it to stop it in the event of a major blow.
Just seems to me that with "tough as nails" turbine assemblies and control gear, and something to *DO* with all the power, the tail is just unnecessary clutter and one more thing to fail?
Wolvenar:
My last long term wind genny I had in the air was a small 6 footer zubbly style motor conversion that had no furling, and ran out full speed. It did end up failing in a spectacular fashion, but it took many unbelievable winds in stride. If I remember right we were topping 120 mph gusts in a massive storm to take it out. The genny was an approx 600 watt in strong winds, it was made from a motor that was originally a 1/2hp motor rewound.
When outside you used to hear that thing in high winds making sounds that would scare just about anyone, but it took it in stride.
With some integration of a 1:1transmission and a heavier shaft, the genny would have survived the blade coming apart, and it would likely still be out there today. The transmission loss would have been negligible as far as losses I would think given I would rather it still been alive making some power.
ChrisOlson:
--- Quote from: rossw on February 12, 2012, 06:04:23 pm ---If you're building turbines that can run balls-out all day and not explode or catch fire, have you considered doing away with the furling tail and all its attendant complexity, cost and weight, and making downwind units?
--- End quote ---
I have considered eliminating it as a furling tail and just place the turbine inline with the yaw as an upwind unit.
I think I'm to the point where I'm reasonably comfortable with controlling the turbine with electronics. Using a very robust generator with gearing provides greatly enhanced control over rotor speed even in very high winds. After I test and tune this one, if it works as expected, it will not need a furling tail and still be able to bring the turbine under control and stop it at 70 mph wind speed, with just the generator, with no damage to it.
When you can use PWM to drive your clipper, using a grossly oversized three-phase clipper load, you can bring a speeding turbine under control very gently with the PWM. And at the same time, match shaft power to the clipper load using the PWM at virtually any speed.
Once I achieve that, you'd better believe that furling tail will be gone and replaced with an emergency parking brake for wind speeds over 70 mph.
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Chris
ChrisOlson:
--- Quote from: Wolvenar on February 12, 2012, 06:43:21 pm ---With some integration of a 1:1transmission and a heavier shaft, the genny would have survived the blade coming apart, and it would likely still be out there today. The transmission loss would have been negligible as far as losses I would think given I would rather it still been alive making some power.
--- End quote ---
Wolv,
The transmissions I build are 95.5% efficient at cut-in and 94.8% efficient at 3.3 kW input power. What that equates to, basically, is 8 watts loss at cut-in speed, mostly due to viscous drag from oil on the chain. At 3.3 kW input it equates to 172 watts loss in the drivetrain, and about half of that is due to the extra set of bearings you have to run when you have two shafts as opposed to one.
On a smaller rotor where you would only have say 1 kW input power, then the efficiency is right at 95%, meaning you'll lose 50 watts in the drive.
There is no "free lunch" with gearing - you have to trade torque for speed to make gains in gen efficiency to get it to work out to a positive net gain. And I think the smaller the rotor, the harder it is to justify using gearing on it.
On these very high voltage turbines I'm building now, it's a hands-down no-brainer to use gearing. There is no way to build generators that put out 180 volts at only .47 ohm resistance @ 400 rpm without gearing, and still get the coils to fit in the stator.
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Chris
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