Storing Cookies (See : http://ec.europa.eu/ipg/basics/legal/cookies/index_en.htm ) help us to bring you our services at overunity.com . If you use this website and our services you declare yourself okay with using cookies .More Infos here:
https://overunity.com/5553/privacy-policy/
If you do not agree with storing cookies, please LEAVE this website now. From the 25th of May 2018, every existing user has to accept the GDPR agreement at first login. If a user is unwilling to accept the GDPR, he should email us and request to erase his account. Many thanks for your understanding

User Menu

Custom Search
« previous next »
Pages: 1 ... 18 19 20 21 22 [23] 24 25 26 27 28 ... 34   Go Down

Author Topic: Shorting coil gives back more power  (Read 461309 times)

giantkiller

  • TPU-Elite
  • Hero Member
  • *******
  • Posts: 2791
    • http://www.planetary-engineering.com
Re: Shorting coil gives back more power
« Reply #330 on: March 16, 2011, 06:54:07 PM »
A higher complex attempt at simplicity

@yssuraxu_,
I see what you are saying about the low windings. I was looking at it from a high current draw and not the collapse specs you mentioned. Thanks.

I have a spool of Litz to put in the configuration.
Logged

popolibero

  • Jr. Member
  • **
  • Posts: 84
Re: Shorting coil gives back more power
« Reply #331 on: March 16, 2011, 07:24:33 PM »
Well, strongly disagree too. If you need to create a certain strength of magnetic field with a coil in this application to work with certain permanent magnets, you can get it with low volt high amps and low impedance coil, OR you can get the same with higher volts lower amps higher impedance coil. With the second you'll loose less through the diodes. This is simple electromagnetics.
A UF5408 is an even better diode.

Mario
Logged

yssuraxu_697

  • Full Member
  • ***
  • Posts: 122
Re: Shorting coil gives back more power
« Reply #332 on: March 16, 2011, 07:27:28 PM »
Quote from: Feynman on March 16, 2011, 06:36:41 PM
Can you explain this to me why this is bad in more detail.  1 ohm is pretty low resistance, so you are talking fractions of an ohm being necessary?

Yep. Fractions. You want your system to have have capability of almost instantly bulding up large current. Just think about shorting the lets say 5uF 220V cap. Screwdriver = proper mini-EMP. Couple of your average thin connection wires with alligators - little sparkie if any.

Currently I'm having huge success with pulse motor drive module following these principles. It already works starting at slightly below 0.1V input. That should speak for itself :) (using classical approach absolute minimum was 1V). At for example 16V it has superb mechanical output AND very little average current usage. How does this click with LV/HC windings? It is driven by mini-EMP bursts that last only a fraction of "normal" cycle and in additon to that most of the flyback gets recycled.
« Last Edit: March 16, 2011, 08:00:20 PM by yssuraxu_697 »
Logged

yssuraxu_697

  • Full Member
  • ***
  • Posts: 122
Re: Shorting coil gives back more power
« Reply #333 on: March 16, 2011, 07:37:23 PM »
Quote from: popolibero on March 16, 2011, 07:24:33 PM
If you need to create a certain strength of magnetic field with a coil in this application to work with certain permanent magnets,

Dynamic characteristics of HV/LC coil you propose are not acceptable for current application because coil is not usable at HF.
LV/HC coil topology I propose is perfectly adequate for HF. The strength is given in form of EMP.

Nothing personal :) Just the truth.

Edit: UF4007 is just an example and I found it to give most output when rectifying shorted coil output with diodes at hand @ ~200V. It is absolutely not suitable for LV/HC part of the circuit, unless you have very tiny setup and/or 1V drop is not a problem.
Logged

popolibero

  • Jr. Member
  • **
  • Posts: 84
Re: Shorting coil gives back more power
« Reply #334 on: March 16, 2011, 08:03:58 PM »
What I wrote is actually more for conventional trafo stuff. You're right that in this application we'd still want a low ohm/impedance coil, else we loose too much in the collapse. In this case taking advantage of higher volts thus less loss because of diode drops is still suitable. The only difference is that at higher voltage we have to increase the frequency (thus switch ON time) for same results. So we would end up with the same setup driven at say 100V instead of 12, and also a high voltage load, but the whole thing driven at a higher frequency. This would be more efficient than a 12V system.
Logged

gyulasun

  • Hero Member
  • *****
  • Posts: 4117
Re: Shorting coil gives back more power
« Reply #335 on: March 16, 2011, 10:06:42 PM »
Hi Mags,

I have to tell (I know you are aware of this  :) ) that generally it is not good to parallel rectifier diodes UNLESS you can select some out of several for nearly equal forward voltage drop at the load current. I agree with what you wrote on the paralleled LEDs.
If someone chooses a rectifier diode type that meets the current and voltage requirements for a task, then there is no problem if the diodes to be paralleled are unselected for a (nearly) uniform forward voltage drop, so paralleling them bring the benefit of less voltage drop. I agree the UF4007 type mentioned here sounds a better choice (a single UF4007 is rated 1000V at 1A and ultra fast) but studying its data sheet it has 1.7V drop at 1A current! ( http://www.fairchildsemi.com/ds/UF/UF4007.pdf )
So paralleling them is a must but maybe searching for another type is also good idea in this case, depending on the actual AC voltage-current amplitudes involved.
I have access to an old transistor curve tracer at work and tested some diodes placed in parallel that is why I wrote those mV values above to Romero. OF course the best way of reducing forward voltage drop is to use low barrier Shottky types, problem with them is they are not high voltage rated (normally under 80 - 100V). PC power supplies have them on their output side (5V, 12V rectifiers placed on heat sinks).
On the heat issue: yes, using paralleled diodes improves the dissipation burden of the individual diodes, remember also that when junction temp is increasing, forward voltage drop is reducing.

Re on MOSFETs used as diodes: see Figure 193 in PDF file Page 193 of this link for the simplest but practical full wave MOSFET rectifier:
http://www.ieeta.pt/~alex/docs/ApplicationNotes/Rectifier%20Applications%20Handbook.pdf

The drawback is you have to make a center tap on the coil and also two small extra coils for controlling (switching) the gates of the MOSFETs (dots show proper phasing of the voltages for the correct control). Basically the body diodes are shunted by the ON resistance of the MOSFET in the correct time so that the voltage drop can be estimated by Ohms Law. IF you use say a RDSon=50 milliOhm FET, then at 2A load current the voltage drop is Vd=2A*0.05 Ohm=0.1V instead of an Si diode's 0.7-0.8V or higher voltage drop.
Here is another good (4 page) paper on this:
http://elth.ucv.ro/fisiere/anale/2007/194.pdf

A full wave bridge can also be made by 4 MOSFETs, however their control circuits becomes a bit involved. I showed an article on such here:
http://www.overunity.com/index.php?topic=6116.msg141191#msg141191  and a direct link to that Electronic Design article is here:
http://electronicdesign.com/print/power/-greener-rectifier-loses-the-diodes-adds-power-mos.aspx 

Gyula


Quote from: Magluvin on March 16, 2011, 06:02:51 PM

I had seen a setup that mosfets were configured to act like diodes. It was very simple, ill see if I can find.

Maybe they could be controlled with timing.  A solid state commutator.

Thats interesting that diodes in parallel can lower the voltage drop of diodes. Never heard that till now. Im surprised that parallel works at all. If we had an led with a limit resistor, it would light when V is applied. But 2 leds paralleled with 1 resistor in series, only one would light. All due to the fact that each led is slightly off tolerance from the next. The one with the lower V drop will be the one that turns on and the other not.  Maybe it is due to the resistor and rectifier diodes are different.

How many volts are we looking at here going through the diodes? If it is high, the dif between .7 and 1 volt drops should make very little difference. But if they do work in parallel, I would have to say that amperage capabilities would help keep the diodes cool, and maybe it is heat that causes the loss. I have had some hot rectifiers before, and maybe I should go back and try increasing the amperage with parallel diodes to see if I was missing something.

Mags
Logged

Magluvin

  • Hero Member
  • *****
  • Posts: 5884
Re: Shorting coil gives back more power
« Reply #336 on: March 17, 2011, 01:47:55 AM »
Hey Guyla

Thanks for the response.  ;]

Here is another example.   I have another, looking for it.

http://mackys.livejournal.com/928372.html

Mags
Logged

Magluvin

  • Hero Member
  • *****
  • Posts: 5884
Re: Shorting coil gives back more power
« Reply #337 on: March 17, 2011, 01:50:11 AM »
This is from the link on that page.

Mags
Logged

Magluvin

  • Hero Member
  • *****
  • Posts: 5884
Re: Shorting coil gives back more power
« Reply #338 on: March 17, 2011, 01:58:48 AM »
One more. It uses a fet to replace the germanium diode in a crystal set. =]

Mags
Logged

yssuraxu_697

  • Full Member
  • ***
  • Posts: 122
Re: Shorting coil gives back more power
« Reply #339 on: March 17, 2011, 02:41:53 AM »
Would add a note about Tesla bifilar vs regular coils. While for drive coil one certainly wants low inductance and fast response and Tesla bifilars are in business, it is a bit mixed bag with shorting coil.

If you look from one side - when shorting there must be rapid current buildup - low inductance helps with that.
If you look from other side - when unshorting there must be large backspike - high inductance helps with that.

So it is very complex problem with multiple variables. I guess some smart dude must do a dynamic über-coil that morphes between low and high inductances inside on shorting cycle :P

For example in the military they get kicks out of charging up big inductance and then get EMP by shorting individual turns step by step.
http://en.wikipedia.org/wiki/File:Flux_compression_generator_2.png
Hmmm......
Logged

Goat

  • Hero Member
  • *****
  • Posts: 640
Re: Shorting coil gives back more power
« Reply #340 on: March 17, 2011, 06:21:56 AM »
Quote from: yssuraxu_697 on March 17, 2011, 02:41:53 AM
Would add a note about Tesla bifilar vs regular coils. While for drive coil one certainly wants low inductance and fast response and Tesla bifilars are in business, it is a bit mixed bag with shorting coil.

If you look from one side - when shorting there must be rapid current buildup - low inductance helps with that.
If you look from other side - when unshorting there must be large backspike - high inductance helps with that.

So it is very complex problem with multiple variables. I guess some smart dude must do a dynamic über-coil that morphes between low and high inductances inside on shorting cycle :P

For example in the military they get kicks out of charging up big inductance and then get EMP by shorting individual turns step by step.
http://en.wikipedia.org/wiki/File:Flux_compression_generator_2.png
Hmmm......

@ yssuraxu_697

Thank you for your input on the Tesla bifilar vs regular coils and the Flux compression generator.

I have been thinking on various Tesla variations of his "Pancake bifilar coils" and the variations of such coils as opposed to normal solenoid coils and also any other coils like stepped or others, I can't help to think that we have barely started to explore in a scientific way what every coil once charged and shorted in the appropriate manner might return to load and source, is there really any extra energy in the right circuit?

As far as the Flux compression generator I can't help to think that there must be energy coming from the high explosive coming into the picture.  The only way to know for sure would be to exclude the high explosive and arrange a mechanical or electronic method to short the coil windings in succession as the high explosive would do.

Could we use diodes or other transistor devices, FET/Zener or other in between coil windings to start a shorting the coil windings in an avalanche?

If you look at shorting a coil such as the secondary of Tesla's patent 609, 250 (see below) for instance, how could one operate the charge/discharge while driving it into a load and feeding back to the source instead of  a single discharge into a spark, can we convert it back to the source with energy to spare?

Hope this makes sense...if not please ignore this post, just thinking ;P

Edit:  I also just thought of something that might be of interest as far as shorting coils.  What about Edward Leedskalnin's Permanent Magnet Holder (PMH), isn't that the same principle of the charge/(short) hold/discharge cycle as what we're discussing here?

Regards,
Paul

« Last Edit: March 17, 2011, 07:05:03 AM by Goat »
Logged

MasterPlaster

  • Hero Member
  • *****
  • Posts: 530
Re: Shorting coil gives back more power
« Reply #341 on: March 17, 2011, 10:45:12 AM »
Quote from: yssuraxu_697 on March 17, 2011, 02:41:53 AM
For example in the military they get kicks out of charging up big inductance and then get EMP by shorting individual turns step by step.
http://en.wikipedia.org/wiki/File:Flux_compression_generator_2.png
Hmmm......

Thank you.

More details here:
http://www.fas.org/sgp/othergov/doe/lanl/pubs/00326620.pdf
Logged

yssuraxu_697

  • Full Member
  • ***
  • Posts: 122
Re: Shorting coil gives back more power
« Reply #342 on: March 17, 2011, 12:26:01 PM »
Hehe, looks like you catch the drift ;)
And as always, DO NOT TRY THIS AT HOME ;)
Logged

MasterPlaster

  • Hero Member
  • *****
  • Posts: 530
Re: Shorting coil gives back more power
« Reply #343 on: March 17, 2011, 01:40:18 PM »
In relation to the above, how about this?

Logged

MasterPlaster

  • Hero Member
  • *****
  • Posts: 530
Re: Shorting coil gives back more power
« Reply #344 on: March 17, 2011, 02:26:16 PM »
And even this one:

Logged
Pages: 1 ... 18 19 20 21 22 [23] 24 25 26 27 28 ... 34   Go Up
« previous next »