If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #1889
Joined: Mon Dec 29 2008, 07:36AM
Location:
Posts: 55
One bank of capacitors works really well with a power supply that charges with 10 Amps and is left on constantly charging the capacitors, not only between firing but also between coils.
I'm using 6 coils and the bank will power them all, this is the reason behind needing a 5kJ power source so that at the end of the chain I won't out of power. With the power supply replenishing a little bit of the energy I will be able to maintain a fairly decent output over 6 coils. Having seperate capacitor banks is very wasteful and I'm trying to achieve high efficiency.
Slotting comprimises the intergity of the barrel. Why would you ever go through all that trouble when you could get as guitardude said, a polycarbonate tube.
Edit: Using osmium oxiode epoxy could be very useful. the reason why other heatsinks don't work is because they have poor surface area contact. if the coil is dipped in os oxide epoxy then left to harden in a mold it will work quiet well but just slapping a heat sink on won't do anything
I'm taking the pictures to give you guys a better idea around 7 or 8 pm EST today because i'm currently out of the house.
Registered Member #968
Joined: Fri Aug 24 2007, 04:54PM
Location: Norman, Oklahoma
Posts: 104
blackgrunge wrote ...
@El_Roberto
Standard 3 inch nails with the heads removed but I'm in the process of getting a Mu Metal projectile made. I looked at the v-switch and it not even close to what I'm using. The v-switch quenches and I have no reason to quench using an SCR because I have a quenching diode for that rated for 4000 amp pulses and has a 800v reverse voltage breakdown rating.
The capacitor doesn't detonate because it pulse through the SCR immediately shutting it off. It basically shorts out the SCR and by the time it is done discharging the SCR is off so it doesn't become negatively charged. I think you may be thinking that the capacitor is negatively charged but its not. It is charge normally and pulsed through the SCR in the opposite polarity as the current is flowing through it. If you copy and paste the link mentioned earlier it might help you understand it a little better. Warning though, using electrolytic capacitors may cause detonation if they aren't able to turn the SCR off. That is why a ceramic capacitor is used instead.
Sorry I wasn't around because of the holidays to elaborate on the v-switch after my initial post. It is not negatively charged, usually it is charged to approx. the same voltage as the main bank. If you time things right with a V-switch you can actually achieve higher peak current just before quenching.
edit: Did you mean you are using a ceramic capacitor or those building V-switches(like EV) are?
Registered Member #1889
Joined: Mon Dec 29 2008, 07:36AM
Location:
Posts: 55
I'm using an electrolyic but its charged to 330v so i'm positive it will turn the SCR off. What I was saying is if it doesn't because you didn't charge it to a high enough voltage, the line voltage of the firing SCR will cause it to detonate
Registered Member #968
Joined: Fri Aug 24 2007, 04:54PM
Location: Norman, Oklahoma
Posts: 104
blackgrunge wrote ...
I'm using an electrolyic but its charged to 330v so i'm positive it will turn the SCR off. What I was saying is if it doesn't because you didn't charge it to a high enough voltage, the line voltage of the firing SCR will cause it to detonate
Gotcha. Capacitance is also important... too much and you lose efficiency, too little and you fail to turn the SCR off. This is hard to deal with I have found. Several parameters like coil resistance, inductance, and SCR shutoff time may remain close enough to "constant" to ignore after initial setup. However, the voltage of the main capacitor bank when you decide to quench depends on both initial charge, as well as how long you wish the firing pulse to be, and so you get stuck with a small amount of wiggle room before swapping caps Caps rated to something like 450v 47uF are slightly expensive to keep replacing.
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
A 10 amp charging supply is too powerful. With such charge rates, you will exceed the dv/dt of the SCR. I have exceeded it with less then 5A input. exceeding the dv/dt of the SCR does not damage it, but it will cause the SCR to trigger with no gate charge. Worse yet, you could exceed the di/dt from this false triggering, which destroy's the SCR. I am speaking out of experience here ( i destroyed 3 3/4in stud SCR's with a surge rating of 6kA for 10ms, the dv/dt and di/dt where high on these too). Your method will be putting lots of stress on the SCR, so you should employ the gate drive recommended for pulse power (Current spikes at 4A/us to 10 times the gate voltage, stays long enough to open, falls down to rated gate voltage, and stays on for the pulse duration).
Did any of your capacitors come with cosmetic defects? a couple of mine came with dents.
Registered Member #968
Joined: Fri Aug 24 2007, 04:54PM
Location: Norman, Oklahoma
Posts: 104
How are you protecting the charging circuit that is on during firing?
Edit: It seems at 10A input(this is before voltage multiplication?) you aren't accomplishing much in terms of charging between/during each stage firing considering you are peaking at over 2kA per coil(guessing)?
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
Keep in mind that it is constant current, rather then 1 pulse of current. Even if 10A is before voltage multiplication, it is still too much current to be safe (assuming your using a bank voltage of 400v. 800v and above would probably be fine).
Registered Member #968
Joined: Fri Aug 24 2007, 04:54PM
Location: Norman, Oklahoma
Posts: 104
rp181 wrote ...
Keep in mind that it is constant current, rather then 1 pulse of current. Even if 10A is before voltage multiplication, it is still too much current to be safe (assuming your using a bank voltage of 400v. 800v and above would probably be fine).
Oh I wasn't trying to say if it was safe or not, I was just wondering how much charging was really being accomplished between stages.
Edit: Also, this will make efficiency very difficult to calculate.
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
By safe i meant the ratings of the SCR's. If it works, i think keeping the charging supply on will help in the later stages. With keeping the charging on, how are you going to measure input energy accurately to get efficiency measurements? EDIT: Doh, beaten to it.
Registered Member #1889
Joined: Mon Dec 29 2008, 07:36AM
Location:
Posts: 55
your obviously don't grasp what is going on a 10A charging input doesn't do anything except charge the capacitors it has nothing to do with the gate....
dv/dt is a calculus function lol. it mean the derivative of voltage with respect to time so it means nothing when related by the SCR. And the SCRs are only ever on for fractions of a second then they are shut off lol.
The voltage multiplier has an output of 330v @10A max. limited by capacitors in series with the AC side of the line. @10 amps my capacitor bank can be charged in around 15 seconds so the energy being dumped into capacitors is substantial. Guitardude as far as measuring the energy input I'm still working on those fine details...
Dealing with a voltage multiplier that has a 10 Amp output isn't unsafe at all. As the capacitors charge the resistance builds up until the voltage makes it up to 330v, then the output goes to to only a few milliamps to replenish the capacitors leakage voltage.
Excuse me if I come off a bit blunt but rp181, charging doesn't work the way your talking about it. The capacitors limit the current. The 10 amps is only the maximum output of voltage multiplier. The charging circuit doesn't need to be protected. Like I said the capacitors on the line side of the AC input limit it so that it the wall socket won't start dumping insane amounts of current into the coils. The voltage multiplier is in parallel with the capacitors so its polarity is exactly the same. The resistance of the fully charge capacitors that are in the voltage multiplier when its on are far greater than the resistance of the coils so its not like the pulse of the main capacitor bank is going back through the charging circuit. I've fired with the voltage multiplier on about 35 times and it doesn't become damaged. What your saying is not realistic.
And yes I already know that a voltage multiplier sends a constant current, I have a college level education in electronics and magnetodynamics. I wouldn't just randomly start leaving things on if i didn't know what the effects were going to be.
I know the capacitors won't being replenished very much by the multiplier during firing. The reason that it is left on is to begin charging as soon as the last coil shuts off. (optical triggering).
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.