Lightweight air core transformer?

Thread Starter

Robert Clark

Joined Aug 6, 2016
35
It turns out the higher frequencies attending practical operation of 'air core' power transformer topologies entail greater radiation and proximity/skin effect losses -- While the latter may be mitigated via 'special' winding technique (e.g. windings fashioned of 'litz wire', etc.) and the former via 'tuned' shielding -- said measures tend to compare unfavorably with ferrite (or Fe powder) core units as regards mass 'conservation' --- Then too are the more stringent resonant capacitor requirements (and, hence, overall driver weight)...
For all that, was there a practical method for power rectification (as opposed to 'detection') at frequencies > 10MHz -- very lightweight DC EHT PSUs would be a 'snap':)
FWIW I strongly urge you to investigate ferrite transformers --- For instance, many LOPTs salvaged from large (CRT) TVs may be operated to 500W well-neigh continuously (in open air):)
Best regards and again good luck!:cool:
HP:)
I have looked at small-sized ferrite transformers available commercially. The best I could find in power(watts) to weight(grams) ratio were in the range of 1 to 3, i.e., to get 10 watts you needed 30 grams weight for the transformer. See for example the ones here:

http://www.ultravolt.com/uv_docs/HPCDS.pdf

But you need this ratio to go in the other direction or at least be above 1 to 1. The reason is due to the lifters limited thrust to power ratio, i.e., how much they can lift for the power input. It's in the range of 1 gram-force per watt. So for instance if you had a lifter running on 10 watts it could lift only 10 grams. But the transformer giving you the high voltage needed would weigh at best 30 grams, so the lifter couldn't raise it.

Bob Clark
 

Thread Starter

Robert Clark

Joined Aug 6, 2016
35
It occurs to me that in that list I linked with the transformers they are giving the power ratings before the transformer would burn out. But that may be due to overheating, not to the electronics burning out. Even if it is the electronic components, diodes, transistors, rectifiers, etc., we could use higher power versions of those. Since the electronics are a relatively small part of the weight this wouldn't increase the weight much but we could then increase the power rating, getting a better power to weight ratio.

If the power rating they cite is referring to burn out due to overheating then there are a couple of things we could do. First since this is for an aircraft application we could use the airflow while in flight to cool the components. We might even be able to remove a heat sink to reduce the weight of the transformer.

Also this is for a proof of principle application right now anyway, so even if we could get a few minutes operation before the transformer burned out that would still be useful.

Bob Clark
 
I have looked at small-sized ferrite transformers available commercially. The best I could find in power(watts) to weight(grams) ratio were in the range of 1 to 3, i.e., to get 10 watts you needed 30 grams weight for the transformer. See for example the ones here:

http://www.ultravolt.com/uv_docs/HPCDS.pdf

But you need this ratio to go in the other direction or at least be above 1 to 1. The reason is due to the lifters limited thrust to power ratio, i.e., how much they can lift for the power input. It's in the range of 1 gram-force per watt. So for instance if you had a lifter running on 10 watts it could lift only 10 grams. But the transformer giving you the high voltage needed would weigh at best 30 grams, so the lifter couldn't raise it.

Bob Clark
What will be the power source for your lifter? Won't a battery be a significant contributor to overall HV supply weight?

Here's an example of an "air" core transformer good for some fairly high voltage. It could be described as a compact tesla coil. The secondary is resonant around 100 kHz so litz is not needed, nor is radiation loss a problem at that frequency. I found it as a surplus item but I've been told that it's used in Glassman high voltage supplies. I'm not sure what it weighs; feels like 100 to 200 grams.

P1000991.png
 

shortbus

Joined Sep 30, 2009
9,065
But you need this ratio to go in the other direction or at least be above 1 to 1. The reason is due to the lifters limited thrust to power ratio, i.e., how much they can lift for the power input.
Have you ever seen one of these that are self powered? Of the many videos I've seen they are all tethered to the power supply on the ground by a wire. Don't think that they have the lifting capabilities to be self powered.
 
I have looked at small-sized ferrite transformers available commercially. The best I could find in power(watts) to weight(grams) ratio were in the range of 1 to 3, i.e., to get 10 watts you needed 30 grams weight for the transformer. See for example the ones here:

http://www.ultravolt.com/uv_docs/HPCDS.pdf

But you need this ratio to go in the other direction or at least be above 1 to 1. The reason is due to the lifters limited thrust to power ratio, i.e., how much they can lift for the power input. It's in the range of 1 gram-force per watt. So for instance if you had a lifter running on 10 watts it could lift only 10 grams. But the transformer giving you the high voltage needed would weigh at best 30 grams, so the lifter couldn't raise it.

Bob Clark
@Robert Clark Yesterday you posted (the relevant part of) the above to your other thread where I showed you an example of a commonly available device capable of > 2W Per Gm HERE :)

And that, kids, it is why it's desirable to confine each topic to a single thread:D

Best regards
HP:)
 
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What will be the power source for your lifter? Won't a battery be a significant contributor to overall HV supply weight?
Indeed, as previously stated, I feel such will be his principal difficulty...

Here's an example of an "air" core transformer good for some fairly high voltage.
FWIW The device imaged in post #65 is a Pie-Wound air core transformer typically employed in ye olde "RF HVPSUs" -- Unfortunately they tend to fail at power levels much greater than 30W and/or operating EMFs > Ca. 25 kV:( --- Tho I'll grant that they're not without their 'old world charm' you'll find them less than useful in applications more demanding than low-power demonstration:( (Typically 25KVP @ 1mA intermittent) Beware, also, The Scourge of The Pie-Wound' Inductor!;) -- CIP Said device is prey of copious self-resonances over it's (ostensible) operating range...

Best regards
HP
 
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Have you ever seen one of these that are self powered? Of the many videos I've seen they are all tethered to the power supply on the ground by a wire. Don't think that they have the lifting capabilities to be self powered.
That's why he requires a 'decent' Power:Mass ratio --- While I believe a small (i.e. ≤ 5 kg), self-contained ion propelled 'drone' might be implemented via electronic PSUs -- larger (manned [personed?:rolleyes:]) designs may (quite counterintuitively) prove more 'amenable' to VDG generator techniques -- That said, Tesla Coils may be worth another look as applied to large-scale designs:cool:

Very best regards
HP:)
 
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Thread Starter

Robert Clark

Joined Aug 6, 2016
35
Have you ever seen one of these that are self powered? Of the many videos I've seen they are all tethered to the power supply on the ground by a wire. Don't think that they have the lifting capabilities to be self powered.
You are correct; that is the key reason why they have not been a practical means of propulsion. The power supplies needed to provide the voltage at tens of thousands of volts are too heavy for the lifters to raise. Do a google image search on "lifters", "power supply", "high voltage". You'll see the lifters are very light weight devices at a few grams, but the power supplies are large and heavy in the range of kilograms.

But actually the batteries needed to supply the power at light weight already exist. It's that last step to convert to the high voltage needed that is the problem.

Bob Clark
 

Thread Starter

Robert Clark

Joined Aug 6, 2016
35
What will be the power source for your lifter? Won't a battery be a significant contributor to overall HV supply weight?
Here's an example of an "air" core transformer good for some fairly high voltage. It could be described as a compact tesla coil. The secondary is resonant around 100 kHz so litz is not needed, nor is radiation loss a problem at that frequency. I found it as a surplus item but I've been told that it's used in Glassman high voltage supplies. I'm not sure what it weighs; feels like 100 to 200 grams.
View attachment 110546
Thanks for that. Interestingly the high power batteries needed already exist. These are used for RC aircraft and drones to provide the high power to drive the propellers and rotors, but at the light weight needed for the aircraft. They are also used for batteries to provide the cranking power to start a car when your car battery is dead, but can yet fit in your shirt pocket.

See for example the batteries for RC aircraft here:

http://www.venompower.com/collections/lipo-airplane-heli-batteries

They get multiple times higher power(watts) to weight(grams) ratios than the 1 to 1 needed for the lifters.

Bob Clark
 
Note: Inasmuch as there seems to be some difficulty with the other thread? - And for 'convenience sake' this is a copy of my latest reply to said location:

Thanks for that. The primary winding is necessary for the transformer operation. So by changing it out, are you referring to decreasing the number of windings on the primary to increase the multiplication factor of the voltage?

Bob Clark
---EMPHASIS ADDED---

Correct -- In practice the original primary/Aux windings (on the lower form leg) are removed and replaced with (typically) 10 to 20 turns each side of a 'center tap point'.

For your information/edification here's an example of a typical 'high power' driver circuit -- NOTE: post continued below image...
MazRoyOsc.png

A few points:

1) -- Please don't be discouraged by the 45V input requirement of the above modeled circuit -- such is readily 'worked around':)
2) -- Output may be either polarity with respect to ground or 'floating'.
3) -- R5 represents the load and was chosen (in the above) to illustrate 600W operation -- much greater power is available with minuscule 'EMF load-down' - Howbeit such operation would rapidly prove thermally abusive to the LOPT:eek:
4) Although the electrical quantities stated in the safety warning (at the bottom of the schematic) apply to a 'dual/complementary implementation' of same -- please be advised that this circuit is very, very hazardous!
5) Please be advised that the circuit leaves much room for improvement/tailoring to specific applications:):):)

In case you're interested, HERE'S A LINK to Aleph(0) and my treatment of this and related circuits/techniques -- in context...

Please don't hesitate to make any further inquires!:)

Have fun and take care!

Best regards
HP:cool:
 

Thread Starter

Robert Clark

Joined Aug 6, 2016
35
That's why he requires a 'decent' Power:Mass ratio --- While I believe a small (i.e. ≤ 5 kg), self-contained ion propelled 'drone' might be implemented via electronic PSUs -- larger (manned [personed?:rolleyes:]) designs may (quite counterintuitively) prove more 'amenable' to VDG generator techniques -- That said, Tesla Coils may be worth another look as applied to large-scale designs:cool:
Very best regards
HP:)
Yes. I wondered about using such electrostatic voltage generators such as the Van der Graaf which can provide hundreds of thousands of volts for the lifters. They usually do these at low current though. I would have to see what is the power output to see if it would work for the lifters.


Bob Clark
 
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Yes. I wondered about using such electrostatic voltage generators such as the Van der Graaf which can provided hundreds of thousands of volts for the lifters. They usually do these at low current though. I would have to see what is the power output to see if it would work for the lifters.


Bob Clark
--EMPHASIS ADDED--

You will please forgive some idle musing... The discovery of fullerenes (Spec CNTs) is a real 'game changer' as regards availability of materials exhibiting ultra-high tensile strength to mass ratios - Moreover, as I understand it, said allotropes' electrical properties (e.g. electrical conductivity, dielectric strength and dielectric constant) may be 'varied' from those of a 'metallic' conductor to nearly that of PTFE via 'doping' - sans compromise of structural properties!

Readly "totable", very high power VDGGs may not be as 'far out' as they sound!:)

Very best regards!
HP
 
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