[TCML] Nevada Lightning Laboratory on Wikipedia

[Greg Leyh]

Hi Stefan,

More on the Lorentz Force can be seen here: 
http://en.wikipedia.org/wiki/Lorentz_force

The NLL will require a primary switch array capable of switching 40kV at 
50kA.  The switch array will consist of hundreds of custom IGBT sections 
in a series-parallel arrangement. Our bench rig for developing and 
testing the high current IGBT sections consists of a water-cooled tank 
circuit, sintered metal resistors and a 3-phase cap charging supply. 
The tank circuit inductor, capacitor and resistor values reproduce the 
frequency, voltage, peak current and ringdown Q that each IGBT section 
will experience in the full-scale NLL system, at full power.

Each time the IGBT section fires, the Lorentz forces work to compress 
the conductors, and expand the diameter of the tank inductor.  This 
produces a notable sound from the conductors, very much like someone 
‘pinging’ the copper pipes with a metal wrench.  Since the operating 
resonant frequency is about 5200Hz, the Lorentz forces are probably 
exciting various mechanical resonances in the copper conductors.  Some 
sections of the circuit are plumbed with wide, thin copper sheet, which 
visibly move during each pulse as well.

I actually consider it a useful feature that the circuit provides a 
pleasant pinging sound when the IGBTs are firing.   GL


> Date: Wed, 5 Jan 2011 15:59:57 +0100
> From: "Teslalabor" <teslalabor at t-online.de>
> Subject: Re: [TCML] Nevada Lightning Laboratory on Wikipedia
> 
> Greg,
> 
>> >  The Lorentz forces produce a pleasing ping note from the copper 
>> > conductors.
> 
> This sounds amazing!!! Could you explain this a little bit more in detail?
> 
> Regards
> Stefan
> 
> 
> 
>