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LAN_403

Electra

Thu Nov 08 2012, 08:16PM

Registered Member #816 Joined: Sun Jun 03 2007, 07:29PM
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Posts: 156

In the second part of the example, I was trying to compare it to a situation where some kind of active switch was used, that basically switched off after the voltage dropped in my example from 1000v down to 800v = 200v difference.
But operating at 5x the frequency, so essentially narrower pulses at 5x the frequency.
Sorry I did not explain clearly enough what I was trying to show.

Ok

E = 1/2L x Isquared, and using E =18mJ

Rearranging for I gives, I = 0.548A (rounded)

If L =12mH

V = L di
-------
dt

T = L x I /V
Using the mean of the capacitor voltage 900V. rearranging and finding T = 7.3us is the time the switch needs to be closed for.

Not sure if Iâ€™ve gone about this the correct way. Or done something wrong as at 5Hz
0.2 / 7.3E-6
The duty cycle works out to be 27,397 : 1

GammaRay

Fri Nov 09 2012, 02:26AM

Registered Member #5323 Joined: Fri Jun 15 2012, 02:14PM
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Posts: 104

Here's the 12 mH inductor image.

Newton Brawn

Fri Nov 09 2012, 03:08AM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Hi GammaRay :

Looking your 12 mH inductor I have two concernings:
1- Insulation between the leads and core. Remember that the voltage between the coil leds (and the wire turns to ferrite core ) has to reach 1000V or more .. so, 4-5 mm of creepage is required.
2- The transfer of energy throgh the coil may be slow..depending of core cross section the core may enter in saturation...

Tell us the inner core ferrite diameter, number of wire turns.
and
What is the input capacitance ?
What is the lenght of your lightning rod ?

Thanks

Tony Matt

Fri Nov 09 2012, 04:01AM

Registered Member #3700 Joined: Sat Feb 19 2011, 12:59PM
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Posts: 107

Hi Gammaray !

Iam very interested in your project and I have some ideas to explain here in the Forum. However, before I'd like to see what you have done suscessefully.

Do you mind to post the complete circuit, including the input capacitor and the LED load ? And the data espec/ of all components ? (only the circuit that works with sucess.)

Your LED minimal current /voltage for minimum visible bright.

Thanks

GammaRay

Fri Nov 09 2012, 10:22PM

Registered Member #5323 Joined: Fri Jun 15 2012, 02:14PM
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Posts: 104

I don't post often, but when I do I am always impressed with the helpful knowledgeable replies. That is why I remain a member. Thanks to all.

I've been thinking about what I am actually trying to achieve, please allow me to reframe my original question:

I am operating on the assumption that there exists a frequency (possibly in the kHz range) at which the inductor L1 and low voltage capacitor C1 combo will achieve resonance and therefore provide the highest conversion efficiency and that if I modulate the HV input on/off at that resonant frequency that I'll get highest conversion efficiency.

Am I correct in this assumption???

Steve Conner

Sat Nov 10 2012, 02:27PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Not necessarily, because the stray capacitances in the circuit get discharged (and the energy in them potentially wasted) at each switching event. Might not sound like a big deal, but consider that one of these stray capacitances is the power source!

GammaRay

Sun Nov 11 2012, 08:21AM

Registered Member #5323 Joined: Fri Jun 15 2012, 02:14PM
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Posts: 104

Newton:

Yep, I have wondered if the inductor was arcing too. So I rolled up a paper (like an old fashioned ear-horn) and placed it between my ear and the inductor and I hear a tick, tick, tick coming from the inductor each time the spark arrestor fires.

I assume the inductor making an audible tick is a strong indication that it is arcing, yes??

Newton Brawn

Tue Nov 13 2012, 12:18AM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Hi Gammaray,

Im waiting from you some information in order to answer you questions:
1 - Tell us the inner core ferrite diameter, number of wire turns.
2- What is the input capacitance of your circuit?
3- What is the lenght of your lightning rod ?

Also there is another post asking for "Do you mind to post the complete circuit, including the input capacitor and the LED load ? And the data espec/ of all components ? (only the circuit that works with sucess.)"

Give information to get answers

Regards

Newton Brawn

Tue Nov 13 2012, 03:42AM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Gamma;
Regarding the tick tick sound from your coil, is because every current discharge through the coil produce a magnetic field around the coil turns. And the coil conductors inside a magnetic field are streesed by a force when the current pass through the conductor.
This phenom were discovered by Andre Marie Ampere ( 1775-1834 ) and lather confirmed by Oersted.
As the turns are loose and not "glued" the turns have small movement as small hammers acting in synchronism with the current discharge produce the tick tick ...

GammaRay

Tue Nov 13 2012, 06:16PM

Registered Member #5323 Joined: Fri Jun 15 2012, 02:14PM
Location:
Posts: 104

I hand modified the schematic to show the circuit. Here are the measurements from an inductor that fell on the floor and broke months ago. The 12 mH inductor inner core diameter is 0 .75 inch, the inner core height is 0.95 inch. The coil resistance is 0.90 ohm, rated at 1.5 amp. Don't know the # of turns without destroying one of the few good inductors I have left or the circuit input capacitance as my meter got fried. For the HV input, I'm using a wire about 3 feet in length with pointed end placed near an ion source, but I've also used much longer wire too. The spark gap S1 frequency can be adjusted by adjusting the value of C2.

1352830505 5323 FT145888 Buck Schematic 20

1352830506 5323 FT145888 Inductor Broken 20

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