Re: diode protection

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

Original poster: "Daniel Barrett by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dbarrett1-at-austin.rr-dot-com>

    Hi!
    My setup is similar and in about the same stage as yours. I'm not sure
what type of diodes you are using, but let me share a few things that may
help. My exuberance and outpouring of funds has been running unclamped on
this PSU for a couple of weeks now ;)

    1) Go ahead, break down and put the reactor under oil. It's messy, and
doesn't sound like fun but It's worth the trouble. Home depot has these
great waterproof electrical junction boxes with no holes in them. My reactor
fit in a 8x8x4 inch model, about $20. If your reactor flashes over you have
just toasted a lot of magnet wire, diodes and time. So invest the time- You
will get good results.

    2) Use fast-recovery rectifiers for the de-queing diodes. 1N4007's will
not survive if used much above 60Hz. I have burned up about 400 of them
learning this. I'm having good luck with Gen Semi UF4007's from Mouser.
These are $.19 each, I use a string of 20. This is a 100v, 1amp, 75nS unit.

    3) you can use a series resitor, but it's not necessary if your
inductors are not flashing over and your caps are not exploding. It just
burns power and acts as an expensive slow-acting fuse. The silicon fries
faster than the resistor...

    I'm running a single MOT feeding a quadrupler feeding a 9H reactor for
20kV at 90mA. Streamers are about 4.5 feet at 1100VA input power as of last
night, power supply is running cool and no fryodes. No protection or
filtering of any kind. Just a lot of mineral oil all over the place ;)
    Hope this helps!
db


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, August 29, 2002 7:14 PM
Subject: diode protection


> Original poster: "Wells Campbell by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <wellscampbell-at-onebox-dot-com>
>
> hi list,
>
> I am working on a small MOT DC maggie, and am currently in the "advanced
> cobble up"stage. Mine is of the type recently discussed, a doubler /
> reactor setup, which I have been able to run at low power a few times.
> As with many on our list, progress has been mainly dependent on the slow
> trickle of funds I have allowed myself to put into the project. I am
> at the point now where the most recent run produced 1 foot streamers
> into open air, and I was able to sucessfully control power by varying
> the break rate on my ASRG, which pleased me greatly. The sound was cool
> too, somewhat like a whiny siren that changed up and down as I dialed
> my variac.
>
> Then my cap (party plates in oil in a bucket, very crude) popped. Time
> to get out the salt and foil and drink some beer!
>
> then my MOT reactors started to flash over (naturally, they aren't in
> oil or anything) and my PS started to eat diodes which (naturally) aren't
> protected or anything.
>
> Anyway, I'm satisfied enough with results so far to start putting together
> the final version, and I had a few questions.
>
> Does anyone have any advice on a diode protection filter arrangement?
> I like Greg Hunter's arrangement, I thought I would use those 10kv /
> .001 uFd ceramic caps at all electronics, one in parallel with each (MO)
> diode. Is this too much capacitance?
>
> Then I was thinking of using a pair of power resistors after the de-Q-ing
> diodes and before the reactors (one per HV leg) to attenuate spikes from
> the reactors, as well as those from any flashovers that may occur in
> the future. What would be a good value? 1k ohms? 100 ohms? Also should
> I use chokes too for an LCR  network, or should I not bother because
> the reactors serve this purpose? what about a safety gap? where would
> it go? seems like anywhere i put it it would power-arc.
> Any advice would be helpful before I pour tens and tens of dollars into
> components :>)
>
> My shematic is similar to the one on Greg's site, "speculative DC reactor
> setup". I will post pics and details soon, but feel I should make a little
> more progress first. My power switch is still an old power strip and
> a bamboo chopstick (i'm not gonna touch that thing!) :>)
>
> Also, a filter that instantaneously clamps outflow of funds as exuberance
> begins positive cycle would be helpful.
>
> Cheers,
>
> --
> Wells Campbell
> wellscampbell-at-onebox-dot-com
>
>
>
>
>