Cyphy has popped up again...

http://www.northeastdronenews.com/start-cyphy-works-developing-high...

What sort of technology is involved in getting 1000W through a filament thinner than headphone cord?

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Hi voltage, good insulation. 500v. X 2Amp = 1000watt. It's nothing special. Now finding 500v esc /motors might b tricky!
I would have thought it would be more than just fitting the maths to suit the cable diameter.
Maybe something with ultra low resistance like superconducting wire.
Superconductors will be very difficult to achieve out in the open , The copper cable resistance increases as the cross section decreases and the the current capacity of the wire also decreases. By increasing the voltage you lower the current required for a load and more importantly lower the losses in the wire. That's why the power transmition wires out on the pylons are at 400kv or more. I still don't see the point of carrying the cable and reels up in copter

I am wondering too. Carrying high voltage dc over such long wires and then using regulator on the drone will not be very efficient. The regulator itself will dissipate a lot of heat/power.

The other option of using high voltage AC and then having a power supply on board is equally challenging. Too much weight.

Both approaches also have the hazard of handling hight voltage in proximity to people.

I wonder if CyPhy could be using something exotic like Tesla's single wire transmission.  Maybe they figured out how to make it work.  Something like this: 

http://viesh.ru/pre/development-of-resonance-methods-of-electric-po...

No they are not using any of that. They are supplying power over a 2 wire system. And they are definitely supplying High voltage and stepping it down in the quad. The questions are 

How High is the voltage?

AC or DC?

is their quad so light and efficient that they are managing with such thin wire and still keep the voltage with safe limits?

I am so interested in this because I am working on something like that that can go about 400ft with ground supply. Needs to stay there for longer periods.

I am having hard time finding something so thin and capable as microfilament.

secondly with heavier wire and powersupply weight, I need more power, that gives even more weight. Its a vicious cycle that only goes up. I have reached a configuration where my hover power is around 1600W despite using lot of carbon fibre for frame.

Thinking more about it, I think they are definitely sending high voltage through the line but I don't think they are using it directly to power the drive system. There is some step down involved. At 1200W such a power supply will not be light for sure. So still puzzled.

I saw this company at the AUVSI Show this may.   Hoverfly has a tethered drone they are selling for about $15,000.00  They are using a transformer on the ground that steps up the voltage, and then another step down on board the drone.   Their tethering system also sent commands to the drone from a joystick on the ground, through the cable and to the drone. 

http://www.hoverflytech.com/all-products-2/

Such a funny concept in the arena of warfare... one pair of scissors...

I wonder if something like this could be made to work:

http://www.digikey.ca/product-search/en?pv1120=1678&FV=fff40009...

110-220V input.  19V DC output, 12A, 1kg.  Could it be de-cased and add a cooling fan, how much could it put out?  At 240W, it's only 2A transmission on the 110V line.

Another idea, is you could use just an AC/AC transformer to step-down, and then a rectifier bridge to turn it to DC.  Something like this:

http://www.digikey.ca/product-detail/en/A41-175-36/595-1302-ND/953172

But I'm surprised it's a whopping 5lbs!  And only puts out 10A?  That doesn't look very viable.  Can you push these things beyond the ratings?  Or am I missing something here?  

Is it better to do the rectification at High Voltage, and then use a switching DC/DC regulator to step-down to your target DC voltage?

220v is still quite low to send over thin wires. Even if you take a 1200W quad, which is just about minimum power to carry a power supply and camera, the current at 220V comes out ot be about 6A. 6A wire will be quite thick. The kind of wires that are being used I wouldn't be surprised if they are sending more than 600V. 

But then the problem is it is very difficult to find supplies that take more than 220V AC or DC and output 12-24v dc.

I am not sure how difficult it will be to modify supplies that are rated at 220V AC to take higher voltages.

220V supplies are plenty and cheap 

http://www.aliexpress.com/item/1200W-24V-110V-input-Single-Output-S...

and after removing there housing and extra moutings they will be less than 2kgs.

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