Electric Powered - High Performance Design

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Tony Williams

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May 10, 2020
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113
NASA has a design with electric motors in the wing tips. They don't need to find stupid investors.
I believe the NASA design is:

1) High wing (so the prop blades don’t hit the ground)

2) Low power per motor

3) A dozen motors
 

Christian Moreton

Active Member
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May 21, 2020
Messages
36
The lithium cells have instant power. There’s no advantage with capacitors.
Capacitors are not “energy storage”.
It's true, Capacitors are not for power storage, they are for cleaning the power up. With electric rotor systems you have a lot of power adjustments and breaking, and the 3 phase power is changing frequency up and down, and this all causes a huge amount of RF noise and interference that mucks up the rest of your electrical, systems. So the way we absorb those spikes is to place a lot of capacitance as close to the motors as possible, before they can find lengths of power cabling to resonate in. In radio they are called common mode currents, will seem like bad ground problems when you rev up.
 
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Tony Williams

Well-Known Member
Joined
May 10, 2020
Messages
113
It's true, Capacitors are not for power storage, they are for cleaning the power up. With electric rotor systems you have a lot of power adjustments and breaking, and the 3 phase power is changing frequency up and down, and this all causes a huge amount of RF noise and interference that mucks up the rest of your electrical, systems. So the way we absorb those spikes is to place a lot of capacitance as close to the motors as possible, before they can find lengths of power cabling to resonate in. In radio they are called common mode currents, will seem like bad ground problems when you rev up.
The inverter is only part of the noise issues with an inductive motor. There’s enough power in there to wipe out bearings and shafts.
 

Tony Williams

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May 10, 2020
Messages
113
This airframe is 2600 pounds with the turbine power plant and prop. Maybe about 2000-2200 without a motor?

By the way, it hauls the bacon with 750-1000 hp.

0A0D375F-529D-4663-8CA9-6B04D838CDEA.jpeg
 

Tony Williams

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May 10, 2020
Messages
113
Much like gasoline or Jet-A, there is a lot of stored of energy that can burn amazingly well when things go bad. It’s super important to protect the airframe during a fire, especially with the fire in a wing.

This picture is cylindrical 18650 cells (18mm diameter x 65.0mm) that caught on fire.

1715A274-6402-48E2-8A5E-780EAAF2E1DD.jpeg
 

Tony Williams

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May 10, 2020
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113
And don't forget to include a venting assembly so that each group of cels can vent hot gas and pressure to the outside of the aircraft to avoid a catastrophic explosion or structural damage if the casing inflates due to high internal pressure.

Yes, that is outlined on the post linked below, with both overpressure and venting to atmosphere for pressure differential while climbing and descending. I suspect that the venting needs to go through an air filter, since air would be going in and out of the battery cells.

The overpressure can just be something simple on the bottom of the wing, like a sticker over the vent. Or a thin layer of paint over the sticker. Hopefully, water will come out that overpressure line.

The process should be:

1) Cell overheats / expands / explodes
2) Fuseable link disconnects it from other cells automatically
3) An overtemp or overpressure indication in any cell sheet:
a. Sets off the fire bell
b. Illuminates the Master Warning
c. Arms the squib
d. Illuminates bottle discharge button. Because there could be dozens of individual battery containers, we only want to flood ONE of them... there needs to be a way to automatically only select the module that is overtemp or overpressure. Also, needs to be an automatic disconnect of high voltage electrically.

 
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Christian Moreton

Active Member
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May 21, 2020
Messages
36
Check out this. Not sure if it's a lot of marketing BS or not but it's interesting to see development in motors with enough robustness and redundancy to potentially be certified for passengers. If lots of smaller manufactures like this can share the load of the many (100's of) millions it will take to develop electric for general aviation, we will get there.

 

Tony Williams

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May 10, 2020
Messages
113
Now you have another problem. You've added lateral loads to those spars, loads that try to twist the spar caps, requiring thicker webs, and that try to spread the spars apart so that much thicker skins are needed to take that tension.

Weight is always the enemy. Always.
Fire is a bigger enemy. Unlike a kerosine or oil fire, lithium batteries (and magnesium metal) can and will burn without oxygen. Those cells need to be in small enough arrangements so that a fire can be contained. The heat cannot get into the spar(s).

I don’t want the weight of making the battery cell containers into a structural member. Perhaps thin stainless steel, or some futuristic lightweight fire resistant material that I’m not aware of should be the cell container.

Air, or a gas like nitrogen, is a great heat insulator for its light weight. The cell container mounting should be coincidental to the ribs, aiding the spars in supporting the cell containers.

49026653-8B33-4E8F-958D-21BF1F5085C6.jpeg
 

Tony Williams

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Joined
May 10, 2020
Messages
113
Check out this. Not sure if it's a lot of marketing BS or not but it's interesting to see development in motors with enough robustness and redundancy to potentially be certified for passengers. If lots of smaller manufactures like this can share the load of the many (100's of) millions it will take to develop electric for general aviation, we will get there.

Two motors are fine, except...

1) It needs a way to reduce propeller speed

2) What if a motor seizes? Answer, with this design, they both freeze apparently
 
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