Author Topic: Estimating spark length voltage  (Read 2288 times)

Offline oneKone

  • High Voltage Engineer
  • ****
  • Posts: 255
  • Karma: +5/-0
    • View Profile
Estimating spark length voltage
« on: September 06, 2017, 02:29:57 AM »
Hey,
A while ago (about 7 years) I read somewhere that a general rule of thumb for estimating a spark length is 1kv for 1mm. I've been blindly using this concept without actually looking into it. I've tried to find some answers but it seems my Google skills are not upto the task!

So basically the question is, is 1kv equal to 1mm or is this far from accurate....... I'm equating my 400mm spark length on my sstc is 400kv.

Cheers,
Chris
« Last Edit: September 06, 2017, 09:59:10 AM by Mads Barnkob »

Offline Mads Barnkob

  • Administrator
  • High Voltage Expert
  • *****
  • Posts: 1048
  • Karma: +16/-0
  • Denmark
    • View Profile
    • Kaizer Power Electronics
Re: Estimating spark length voktage
« Reply #1 on: September 06, 2017, 09:58:05 AM »
The old 10 kV/cm rule does not apply here, I seem to recall that it is for DC current between pointy objects, the attached short description goes into further detail on the required breakdown voltage for different spark gap geometries.

Tesla coils does however operate quite differently. We charge up a topload, secondary top capacitance, with as many electrons as possible, before the voltage is high enough to break down the dialectric strength of atmospheric air. This can differ with temperature, moisture and pressure.

The topload voltage will always be the greatest just before there is a spark formed, as this is when the charge is at its highest, once the spark starts to grow it represents a larger and larger load to the topload and as current goes up while discharging the energy, the voltage drops significantly.

This is just a bold statement, that for a Tesla coil we are more in the league of 3 kV/cm for long sparks. Terry Fritz once made some measurements on this: https://deanostoybox.com/hot-streamer/TeslaCoils/MyPapers/planant/waveant3.html

Hydron also posted a lot of topload/breakout point current measurements, these numbers can be used to calculate the topload voltage: https://highvoltageforum.net/index.php?topic=117.msg735;topicseen#new
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline Uspring

  • High Voltage Technician
  • ***
  • Posts: 105
  • Karma: +8/-0
    • View Profile
Re: Estimating spark length voltage
« Reply #2 on: September 06, 2017, 04:47:14 PM »
The differences between DC and AC arcs are mainly 2: An AC arc can end in midair and it usually lasts much longer. The AC arc can grow over many cycles by current flowing back and forth along it, keeping it hot. So once a small arc has broke out, it will establish a conductive channel to its tip from where the arc can grow further. The arc channel won't be a perfect conductor, so the voltage at its tip will gradually decrease as it gets longer. This will basically limit its length. In principle arc length and voltage don't even have to be linearly related. Probably higher frequency arcs are also longer for a given voltage, since charges are more often pushed back and forth, making it hotter and more conductive.

If you're into math, you might want to read https://www.pupman.com/listarchives/2012/Oct/msg00125.html

A back of the envelope calculation based on Hydrons data seems to indicate a voltage of about 300kV for an arc length somewhat above 2 m, i.e. 1.5kV/cm.

Offline oneKone

  • High Voltage Engineer
  • ****
  • Posts: 255
  • Karma: +5/-0
    • View Profile
Re: Estimating spark length voltage
« Reply #3 on: September 07, 2017, 01:40:46 AM »
Cheers for the replies and the links. Looking forward to understanding further

Offline AndreiRS

  • High Voltage Experimenter
  • **
  • Posts: 69
  • Karma: +0/-0
    • View Profile
Re: Estimating spark length voltage
« Reply #4 on: February 17, 2018, 12:12:40 AM »
I couldn't get an arc from a mot with 2kv output, at something like 0.3 maybe 0.4mm. It depends a lot on air humidity.

High Voltage Forum

Re: Estimating spark length voltage
« Reply #4 on: February 17, 2018, 12:12:40 AM »

 


* Recent Topics and Posts

post CM300 coil build questions
[Dual Resonant Solid State Tesla coils]
acobaugh
Today at 05:32:28 AM
post Re: Welcome new members, come say hello and tell a little about yourself :
[General chatting]
ElectroXa
July 20, 2019, 09:45:42 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
Bert911
July 19, 2019, 11:19:45 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
hightemp1
July 19, 2019, 03:36:44 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
DICKEYBIRD
July 19, 2019, 03:24:38 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
hightemp1
July 19, 2019, 02:23:29 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
DICKEYBIRD
July 19, 2019, 01:06:44 AM
post Re: Floppiclene! A Electronics Cleaning Relic of the Past.
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Justin
July 18, 2019, 10:29:32 PM
post Re: Floppiclene! A Electronics Cleaning Relic of the Past.
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Mads Barnkob
July 18, 2019, 08:52:35 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
hightemp1
July 18, 2019, 05:49:27 AM
post A new quick way to get into tune a DRSSTC
[Dual Resonant Solid State Tesla coils]
VNTC
July 18, 2019, 03:13:27 AM
post Re: Floppiclene! A Electronics Cleaning Relic of the Past.
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Twospoons
July 18, 2019, 12:06:53 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
hightemp1
July 17, 2019, 07:56:41 PM
post Floppiclene! A Electronics Cleaning Relic of the Past.
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Mads Barnkob
July 17, 2019, 11:25:22 AM
post Re: Next Gen DRSSTC
[Dual Resonant Solid State Tesla coils]
Netzpfuscher
July 16, 2019, 07:39:33 AM
post Re: What is the true in tuning guide?
[Dual Resonant Solid State Tesla coils]
VNTC
July 16, 2019, 05:11:21 AM
post Re: Next Gen DRSSTC
[Dual Resonant Solid State Tesla coils]
profdc9
July 16, 2019, 04:05:07 AM
post Re: DRSSTC in brust mode
[Dual Resonant Solid State Tesla coils]
SAMGO
July 16, 2019, 02:25:27 AM
post Re: Next Gen DRSSTC
[Dual Resonant Solid State Tesla coils]
Hydron
July 16, 2019, 01:54:30 AM
post Re: Next Gen DRSSTC
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
July 15, 2019, 02:51:26 PM
post Re: What is the true in tuning guide?
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
July 15, 2019, 02:48:02 PM
post Re: A problem solved with hand tools
[General chatting]
Mads Barnkob
July 15, 2019, 01:48:08 PM
post Re: Kaizer half bridge driver
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
July 15, 2019, 01:45:00 PM
post Re: A problem solved with hand tools
[General chatting]
Hydron
July 15, 2019, 11:21:29 AM
post What is the true in tuning guide?
[Dual Resonant Solid State Tesla coils]
VNTC
July 15, 2019, 10:01:21 AM
post A problem solved with hand tools
[General chatting]
klugesmith
July 15, 2019, 07:52:41 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General chatting]
klugesmith
July 15, 2019, 07:33:30 AM
post Re: tesla coil varnish is dumb
[Solid state Tesla coils]
Hydron
July 14, 2019, 10:49:03 PM
post Re: tesla coil varnish is dumb
[Solid state Tesla coils]
T3sl4co1l
July 14, 2019, 09:59:40 PM
post Re: tesla coil varnish is dumb
[Solid state Tesla coils]
Mads Barnkob
July 14, 2019, 08:20:52 PM
post Re: Next Gen DRSSTC
[Dual Resonant Solid State Tesla coils]
Netzpfuscher
July 14, 2019, 06:06:30 PM
post tesla coil varnish is dumb
[Solid state Tesla coils]
Fumeaux
July 14, 2019, 05:29:10 PM
post Led Closeups with Mobile phone and lens .
[Smart phones]
DashApple
July 14, 2019, 03:00:09 PM
post Re: Drsstc 3
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
July 14, 2019, 02:06:26 PM
post Re: DRSSTC in brust mode
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
July 14, 2019, 02:04:22 PM
post Re: Twin System Build
[Dual Resonant Solid State Tesla coils]
oneKone
July 14, 2019, 01:27:18 AM
post Re: DRSSTC in brust mode
[Dual Resonant Solid State Tesla coils]
johnf
July 14, 2019, 01:22:15 AM
post Re: Drsstc 3
[Dual Resonant Solid State Tesla coils]
oneKone
July 13, 2019, 03:48:54 PM
post DRSSTC in brust mode
[Dual Resonant Solid State Tesla coils]
SAMGO
July 13, 2019, 04:17:55 AM
post Re: Kaizer half bridge driver
[Dual Resonant Solid State Tesla coils]
donnersm
July 12, 2019, 08:54:54 PM
post Re: Kaizer half bridge driver
[Dual Resonant Solid State Tesla coils]
profdc9
July 12, 2019, 07:16:40 PM
post Re: Kaizer half bridge driver
[Dual Resonant Solid State Tesla coils]
profdc9
July 12, 2019, 06:33:00 PM
post Smooth corona or heavy spark, RF wave radiation frequency of Tesla coil drops ve
[Dual Resonant Solid State Tesla coils]
VNTC
July 12, 2019, 11:09:28 AM
post Re: Drsstc 3
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
July 12, 2019, 09:56:38 AM
post Re: Drsstc 3
[Dual Resonant Solid State Tesla coils]
oneKone
July 12, 2019, 01:23:58 AM
post Re: Completed my pulsed power generator
[Capacitor banks]
MRMILSTAR
July 11, 2019, 05:48:27 PM
post Re: Completed my pulsed power generator
[Capacitor banks]
Mads Barnkob
July 11, 2019, 02:58:13 PM
post Re: Kaizer half bridge driver
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
July 11, 2019, 02:45:24 PM
post Kaizer half bridge driver
[Dual Resonant Solid State Tesla coils]
donnersm
July 11, 2019, 06:59:01 AM
post Completed my pulsed power generator
[Capacitor banks]
MRMILSTAR
July 11, 2019, 05:43:31 AM

Sitemap 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30