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Forty

Wed Mar 28 2012, 07:19PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

use this to simulate a coil

I'd pick a fixed inner diameter and length (the size of something you might wrap the wire around), a magnet wire size that you have, and then adjust the outer diameter slider and record the R and L values for each number of layers. Then take that table of values to here:

and then you can play around with the voltage and capacitance values to see what the pulse will look like. Increasing R (more turns or thinner wire), Increasing L (more turns or larger diameter), or Increasing C will make the pulse longer and affect the peak current. And Increasing V will just affect the peak current.

The number of turns from the first sim, along with the peak current from the second, and times the permeability of free space will roughly give you the magnetic field strength with no core.

The_Happy_Duck

Thu May 10 2012, 02:13PM

Registered Member #4089 Joined: Fri Sept 09 2011, 04:40PM
Location:
Posts: 19

Hello,
Sorry for bumping an old thread but I have not had chance to start this project due to exams.

I am still a little confused on the calculations,
I am also not sure how current works with capacitors.

Just out of curiosity I am going to list a few assortments of capacitors; I hope you can tell me which set would be the most effective to use in an EMP, creating the largest radius possible. I also hope you could tell me how your worked it out. (I am comparing these by cost, not a good measure I know)

3000 Capacitors; 1000pF 1KV
35 Capacitors; 330uf 0.160KV
10 Capacitors; 150uF 0.5KV

(Please note I am not going to start building anything until I know what I am doing, especially with these quantities.)
Thank you for all the help.

Forty

Thu May 10 2012, 07:22PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

the banks would hold
1.5J
147.84J
187.5J

Could probably make a coilgun with the 3rd one, but i doubt any of them would be suited for an emp pulse.

something like a defibrillator capacitor, a bunch of microwave oven capacitors, or any other high energy discharge/pulse capacitor would be better suited for the fast pulse you need for an emp. Playing around with any of those would be extremely dangerous though, so I wouldn't recommend that you do it without a lot more experience.

The_Happy_Duck

Fri May 11 2012, 09:38AM

Registered Member #4089 Joined: Fri Sept 09 2011, 04:40PM
Location:
Posts: 19

I actually meant by '3000 capacitors' that each one had 1000pF and 1KV, was this taken into account? I was comparing tiny ones to larger ones. I am guessing you were using the equation; 0.5*C*V^2?

Edit; I did the calculation and got the same answer, never mind

Can you take a look at this for me?;
http://www.sourcingmap.com/300uf-15kv-30kw-threaded-ceramic-door-knob-high-voltage-capacitor-p-200473.html?currency=GBP&utm_source=google&utm_medium=froogle&utm_campaign=ukfroogle
My calculations say that this would output 33,750J, I don't think that can be correct.
What am I getting wrong here?

Also could you give me some indication of what a good energy output would be?

Mattski

Fri May 11 2012, 02:42PM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

wrote ...
Can you take a look at this for me?;

My calculations say that this would output 33,750J, I don't think that can be correct.
What am I getting wrong here?

Your calculation is fine, the problem is that the specs are wrong. No way is that capacitor 300uF, it's probably 300pF. So instead of 34 thousand joules it's 34 thousandths of a joule.

The_Happy_Duck

Fri May 11 2012, 06:38PM

Registered Member #4089 Joined: Fri Sept 09 2011, 04:40PM
Location:
Posts: 19

Mattski wrote ...

wrote ...
Can you take a look at this for me?;

My calculations say that this would output 33,750J, I don't think that can be correct.
What am I getting wrong here?

Your calculation is fine, the problem is that the specs are wrong. No way is that capacitor 300uF, it's probably 300pF. So instead of 34 thousand joules it's 34 thousandths of a joule.

Ah, ok thank you.
Another thing, I thought one joule was a tiny amount of energy?
I thought it was not used in electric bills because it is so small so instead they used kWh's?

Harry

Fri May 11 2012, 07:19PM

Registered Member #4081 Joined: Wed Aug 31 2011, 06:40PM
Location: UK
Posts: 139

Correct, 1 joule is nothing. A kWh is 3.6 million joules, for perspective.
But it is the rate of energy transfer that is important with EMP's, and in general, capacitor experiments. A 1000J could be used in 1 second in a heater at 1000W, but in a 100 microsecond capacitor experiment it will reach (1000j/0.0001) 10 000 000W or 10 million watts, realistically this figure is lower because of resistance and inductance in circuits.

The_Happy_Duck

Fri May 11 2012, 08:19PM

Registered Member #4089 Joined: Fri Sept 09 2011, 04:40PM
Location:
Posts: 19

Harry wrote ...

Correct, 1 joule is nothing. A kWh is 3.6 million joules, for perspective.
But it is the rate of energy transfer that is important with EMP's, and in general, capacitor experiments. A 1000J could be used in 1 second in a heater at 1000W, but in a 100 microsecond capacitor experiment it will reach (1000j/0.0001) 10 000 000W or 10 million watts, realistically this figure is lower because of resistance and inductance in circuits.

I am guessing that discharge time varies with capacitance?

The_Happy_Duck

Sat May 12 2012, 02:40PM

Registered Member #4089 Joined: Fri Sept 09 2011, 04:40PM
Location:
Posts: 19

Another question regarding these capacitors,
Would something like this be suitable;

I am thinking it would not make a very good EMP due to the capacitance but I am not sure, all of these capacitors with over 1 Farad seem to hold a good yield. I am still searching for those big blue capacitors which everyone with washer launchers seem to own.

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