Capacitor blasts and automatic impedance matching

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Real name: Ian Krase

Capacitor blasts and automatic impedance matching

Post by ian_krase » Thu Sep 06, 2018 2:38 am

I am sort of curious whether there's any practical circuit that automatically does some form of impedance matching on capacitor discharges -- can crushers, spot welders, flashlamp flashers, etc.

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Richard Hull
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Real name: Richard Hull

Re: Capacitor blasts and automatic impedance matching

Post by Richard Hull » Thu Sep 06, 2018 5:14 am

Complex question with no computational answer without a detailed experimental effort. What is the impedance of the load?....The source?

Capacitors have tricky ESRs and inductances based on the construction and the "blasting" as you say over a giving period of time.

If you are blowing something up, Water Arc explosions, wire explosions, destructive testing, etc. You must realize the time frame of the destruction and opening of the circuit is critical. All current prior to rapid destruction will travel only on the surface of any conductor between the capacitor bank and the item being "blasted" This is why not so thick sheet metal of large area and near zero distance between the capacitor and that to be "blasted" is a must. (Big round 000 copper conductors are a waste of copper) This typically is all you can do and impedance matching is somewhat impossible and senseless as there will be no oscillation in the circuit. As there is, ideally, no inductance in a well done destructive, "blasting" circuit, You are banking on a huge di/dt and no oscillations.

Slower discharges where reversals and damped waves are the order of the event would have to be observed with scopes and high speed current xfrmers.

It is all about the di/dt warranting the effective use of amp turns if you are launching something magnetically

In the case of magnetic propulsive discharges, Rail guns, ring launchers, Inductance is a big issue and one will struggle to observe on a scope and HF current CT that the device being projected leaves the rail or iron launch laminations before the first zero crossing or the reversal of the mag field might retard the device. You really do not want a high Q circuit with magnetic launchers. All the energy needs to be dumped in that first rise of impulse current. With amateur ring tossers, the inductance is typically huge.

Many have studied this in some detail in the past and in the present. Papers and reports abound, but for amateur work, a good scope and high frequency capable CT will tell the tale on how much energy you are delivering on target.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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