need ideas - magnetic disruptor analog

[darkspeed]

I have a 20A 5000V DC moving through a coil, i need to place a device after the coil that will break the circuit / stop the flow in a very short period of time.

Thyratron?

Diodes in reverse?

Any good ideas?

I need something that works as a analog to my magnetic disruptor for comparison..

Thanks guys!

[Peterae]

Thats 100 Kw 

[darkspeed]

Thats why it needs to be a short pulse

5000v into 250ohm as a pulse

[BEP]

I have a 20A 5000V DC moving through a coil, i need to place a device after the coil that will break the circuit / stop the flow in a very short period of time.

Thyratron?

Diodes in reverse?

Any good ideas?

I need something that works as a analog to my magnetic disruptor for comparison..

Thanks guys!

Why 'after' the coil?

[Ken]

Ground it.


KABOOM!!

[darkspeed]

What i am doing works best with ringing the coil with hf while keeping a positive bias, so i need to quickly switch off  the negative side.

I have a mechanical break on the negative side, it is just not fast enough so i need to break the circuit as soon as the mechanical makes.

The mechanical is so long that it washes out all the good hf

[Ken]

Sounds to me like you might need a Sprytron.

[BEP]

Even a Sprytron is designed for fast 'ON' time with little control of the 'OFF' time. OFF time is highly dependent upon the source of energy being switched and the environment. OFF times can be around 100ms.

For fast off times use a self-quenching triggered spark gap. The ON time is limited to the time it takes to buildup the ionization channel for the main gap and then the quenching gap. You can build it yourself.



The problem with this, for your request, is it shorts itself out to have OFF times as fast as the ON time.
Note: This gap configuration also rectifies.

[Peterae]

And dont forget the safety equipment needed to operate the above devices, notice in his right hand he is holding a quick disconnect device  

[BEP]

And don't forget the safety equipment needed to operate the above devices, notice in his right hand he is holding a quick disconnect device 

Below is my discharge bank for the self-quenching spark gap trigger for my EMP. Sorry, the IGBTs cracked on my last firing.
This little one comes to 1.9F @ 800V. The spark gap for the EMP melted and needs a rebuild. It had 3/8" silicon-bronze gold-plated gaps.

More like a dead-man switch 

[Peterae]

And by any chance was this your last known address

It's quiet easy to see where the front door would have been, i presume the garden path once ended at it.


Sorry Ds didn't mean to derail your thread. :

[BEP]

Yes but I didn't wish to reveal my true age.

After that test I moved to Tunguska. Been a couple of places since.  

DS,

Can you post a sketch of your intent? I'll see if my spark gaps will do it for you.
Example:

What is your source of 5000V @ 20A?
What is the construction/design of your coil? (the stuff I mess with easily vaporizes most coils)

[darkspeed]

Its almost a basic tesla primary

15kv 11uf pulse capacitor positive > ultrafast diode bank > very low ohm coil > ( this is where the fast quench needs to go ) > rotary gap > 15kv 11uf pulse capacitor negative.

At the moment i have a solid compressed carbon tube pulse resistor just after the cap + to limit the amps - mostly not to pop the diodes

[darkspeed]

This may be the way to go as i have some large thyratron's on hand  -

http://translate.google.com/translate?js=y&prev=_t&hl=en&ie=UTF-8&layout=1&eotf=1&u=http%3A%2F%2Fwww.rapp-instruments.de%2Ftesla-coils%2Fthyratron%2Fthyratron.htm&sl=de&tl=en

http://www.rapp-instruments.de/tesla-coils/thyratron/thyratron.htm

[BEP]

DS,

note: a Thyratron is only slightly faster than a common SCR for turn-off. You can have faster off times by running the tube filament and/or plate/cathode voltages lower. (not common knowledge) Go too low and the turn-on time increases.

I've used many, including Hydrogen types. Any type can handle a huge amount of energy - they are more durable than any SS device I've used - but they are too slow on turn-off for my more advanced toys.

The self-quenching spark gap (the one which has a second gap to short the first) has shutdown time down to less than half the pulse width.

[darkspeed]

WW - do you have any photos of your gap you could post?

WW - I know they are slow but I was thinking of using the tube as a hold off until the end of the mechanical dwell - so it would fire as the mechanical was about to open.

[Ken]

Yes but I didn't wish to reveal my true age.

True age? Were you around when the earth was flat?

[BEP]

True age? Were you around when the earth was flat?

I don't recall the Earth ever being flat. When that hole was created my stomach was flat 

[BEP]

WW - do you have any photos of your gap you could post?

WW - I know they are slow but I was thinking of using the tube as a hold off until the end of the mechanical dwell - so it would fire as the mechanical was about to open.

No photos, yet. I'll do some digging. I ran three in sequential firing for rotation. One of them should be presentable.

Mechanical dwell? This was used for quenching, was it not?
If so, you won't need it with mine. Look at the schematic symbol I posted above.

TRG = Trigger for the primary gap. Apply a very high voltage here to start ionization at the cathode of the primary gap. This makes the gap more conductive for the main energy applied to SRC.
SRC = Source. Source of voltage to do the work. Genrally, I apply a lower voltage much higher current capacity here. This voltage is usually so low it would never arc across the gap without a trigger.
OUT = Output to the load
GND = Ground here but can also be the next SRC in a sequence or TRG to the next gap.

Note the second trigger near the GND terminal. This is what I have not seen by others. When the main gap does fire that same potential is applied to the GND trigger. This builds ionization at GND making the lower gap more conductive than the primary gap.

The primary gap is truly quenched. Not by air, magnets, steam, water, arc chutes or mechanical mechanisms. All are far too slow.

By adjusting triggers and gaps you can have your load switched off right at the peak. The results are interesting enough without encasing the thing in a vacuum or some special gas. Humidity and dust do nasty things to performance.

Just use fine thread for adjustments and well insulated adjusting knobs. My parts all came from Lowe's and Menard's. The gold plating was done at work. I have used Tungsten arc cutter tips before for gap points from a weld shop supplier.

[Paul-R]

If we can find someone in industry using 20a at 5kv, they will have a solution.

What about Cern? Do they have a need for such a switch?

[BEP]

If we can find someone in industry using 20a at 5kv, they will have a solution.

What about Cern? Do they have a need for such a switch?

You must be speaking of continuous. My EMP trigger boards (the driver for the main gaps) fire 30A @ 8kV.
Besides, CERN wants to bang particles. I doubt they are concerned about the 'off' time of a pulse. They probably read a scope backwards like most folks.

(Haven't found the main gaps yet but stumbled upon the trigger boards. You can fire my gap triggers with almost anything pulsing 2- 20kV. Complexity depends upon what amount of control you wish.  )

[Grumpy]

What i am doing works best with ringing the coil with hf while keeping a positive bias, so i need to quickly switch off  the negative side.

I have a mechanical break on the negative side, it is just not fast enough so i need to break the circuit as soon as the mechanical makes.

The mechanical is so long that it washes out all the good hf

Apply the bias from a separate circuit, perpendicular to the radial force, (This is verticle in the case of a flat horizontal coil.), then you can reduce the current to the minimum required to complete the circuit.  You can use an external coil powered by batteries or a separte DC supply.

I found that a delay line will quench as fast or faster than a magnetic gap, and is more consitent.  If you want to keep the high current pulse rather than a separate bias, try delay lines on each side or on the neg side.  The delays can be different lengths.  From Tesla's notes, the balanced system with caps on bith ends of the coil was the most powerful but hardest to tune.  With this approach, you'll have to switch each side at the same time.