THOR episode II (was Re: My Licentiate degree)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Marco Denicolai by way of Terry Fritz <twftesla-at-qwest-dot-net>" <marco.denicolai-at-tellabs-dot-com>

Hello all,


Thanks very much for your interest in the Thor project.

Tesla list wrote:
> 
> Original poster: "Loudner, Godfrey by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <gloudner-at-SINTE.EDU>
> 
> Hi Marco
> 
> Congratulations! I am wondering if you get to keep Thor, or will other
> people continue the research using your Thor?

Thor is propriety of the High Voltage Institute (which payed for its
components): I couldn't even arrange a decent place for it in my
backyard :)
Outside of the degree work (which is concluded) and of future degrees,
there is still much work to be done to increase the reliability and
usability of Thor. I have still to fill a "Thor folder" with all
schematics, PCB layouts, etc, and a "Thor user manual" with instructions
on how to operate the CCPS properly. These two items are intended to be
available to the Thor user (i.e. not necessarely me), not for my
personal joy at home.

About the reliability, my CCPS is as much robust as it can be, resisting
to spikes, transients, noise, EM interference. The only thing it still
doesn't like are power injections (not only transients) on its output
terminals, i.e. the toroid arcing to the primary.

One mounth ago I had a toroid streamer curving down and hitting the RSG
stationary electrodes -> some HV diode bridge sections had to be
replaced. I enclosed the RSG assembly in a grounded shield assembly.
Then, last week, I was having again 3 m long streamers when one of those
hit the primary. This time one driver board was seriously damaged: I am
still repairing it.

Just to tell you about the effect chain:
as the CCPS output is a floating supply (a rectified transformer
secondary), the streamer probably induced a fat transient from the
transformer secondary back to its primary. The primary is actually fed
with a rectified 3-phase 230 VAC (no isolation!).
On one driver, I had the rectified 560 VDC arcing to the 230 VAC phase,
vaporizing big sections of PCB copper and roasting even their backplane
connections. Every single semiconductor on the board (i.e. all IC's, all
diodes, all regulators, all IGBT's, etc) have been damaged, including
several 1/4 W resistors. A real disaster...

I have a safety gap between the CCPS and the coil: probably it helped a
little bit, but not enough. Also all 230 VAC safety fuses got triggered,
but they are so slow... 

The problems with protecting the CCPS from these sort of things are:

- fuses, even FF fuses (I got them) are still too slow. Guess if you
need HV fuses or HV relays...
- voltage triggered switches (e.g. SCR) must satisty two opposite
requirements: be VERY fast in getting triggered and avoiding to get
triggered from harmless transients (which are really abundant, as you
know)

That's why I prefer to prevent the arcing instead of preparing myself to
it. More on this on my next email.

Regards

-- 
_____________________________________________________________

 Marco Denicolai           Senior Design Engineer 
 Tellabs Oy                tel: +358 9 4131 2769
 DSL Products              mobile: +358 50 353 9468
 Sinikalliontie 7          fax: +358 9 4131 2410
 02630 Espoo  FINLAND      email: marco.denicolai-at-tellabs-dot-com
_____________________________________________________________