Generators for hybrid systems

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akwrencher

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I have seen many threads about hybrids, and have yet to see any real discussion about the generator part. Are there any lightweight generator heads available today off the shelf? All the gen sets I am aware of are pretty heavy with the exception of very small portable high rpm "inverter" series generators. I have no info at hand, but figured someone should pose the question, since total power plant weight is always a critical issue.

*I'm not really for or against hybrids, I think the idea is neat for certain aplications but fail to see how it could be made light enough to be truly useful. Anyone care to enlighten me/us? (No pun intended, but I'll take it...)
 

pictsidhe

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I've been pondering a motorgen for my 103. Minimising the power loss while it isn't doing much is a major design consideration. I'd like to replace the existing weedy generator with a 10hp motorgen. Extra weight would then be small and I'd get a bigger flywheel, which makes TV easier to deal with. But iron losses would be fairly high with a conventional brushless motor. A toothless motor is going to be looked at. That would also have the benefit of an easy to make stator. Stack laminations, true in a lathe, etch the burrs off in FeCl.
I really ought to look into the Prius motorgen, I suspect it is one of the better ones.
Look at the RC brushless motors for high power to weight at a reasonable cost.
 

karoliina.t.salminen

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Oct 7, 2008
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I think best working example you can see is the Pipistrel's hypstair project. I think it has Siemens electric motor both as generator and drive motor (two motors because it is series hybrid). The motor is mounted directly to the Rotax drive shaft with the reduction gear removed. The generator's control electronics are likely from Siemens as well. There are many ways to do series hybrid, but from off the shelf components, this is the best one that already works. Search keyword hypstair from Youtube to see it in action.

Another way you could do it, would pay salvaged Tesla, and use one motor as generator and the another as drive motor. You need custom ESCs for it because Tesla's own does not have suitable software on it for other than Tesla car use. Someone had made Lotus to EV conversion with Tesla model S parts, and that would be another good example. It would be good idea to also use some battery pack as buffer between the generator and motor that would allow higher power output on takeoff run. Tesla-like 700 hp on takeoff would be rather awesome and even taking half of that would be very good takeoff power for small GA plane. The hybrid allows using a small fraction of takeoff power as cruise power so the difference for takeoff power and economy cruise can be massive. Of course discharging the pack rapidly to get the 700 or even 350 hp out without damaging the cells, requires quite large pack with enough cells wired parallel and that unfortunately weights some xxx kg.
 

karoliina.t.salminen

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And if you think of the portable generators out there, here is where you would go wrong. There is no practical way to use these in airplane because the power to weight ratio is too poor and the power output is too poor. Only way to successfully do a hybrid is to use a brushless motor as generator (BLDC or AC) and mount it to shaft of some engine such as in Pipistrel's case the 135 hp upcoming Rotax model with the reduction gear removal modification. Another fairly doable way IMO would be to buy a motorcycle engine to turn the motor. Such as Hayabusa engine or perhaps Kawasaki ZX10R engine, but the latter may be the less reliable option. You could remove all other gears than the highest gear from gearbox or lock it to the highest gear. The electric motor needs nothing else itself than being turned at high rpm (motorcycle engine is better than other types because it can reach more reasonable rpm for the motor (eg 7000-8000 rpm continuous) to produce electricity. Some efficiency gets lost in the energy conversion twice. But it is reasonable/acceptable loss taking account the benefits.
 
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