Re: Voltage Multiplier(4x) problems

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

Original poster: "Peter Terren" <pterren-at-iinet-dot-net.au> 

Nice set-up.  However, some potential problems to consider (before you blow
your diodes).
Firstly, if you don't have one side of your supply earthed (the one that
connects to the diode first then you will have all voltages above ground
potential.  Any spark to ground (or corona leakage) will have to return
through a path that is unintended such as across your transformer core to
the secondary (assuming it is grounded).  If it is not grounded then you
will get sparks to the primary.
Secondly, don't use the multiplier for sparks.  The peak current rating of
the diodes might only be 30 A or so. A spark will exceed this current and
your diodes will fail eventually.  To be safe, use a dropping resistor rated
for 10 kV to limit current to 10 A i.e. use at least 1000 ohms made up of 10
times 100 ohm 1 watt resistors. You can draw sparks off this or for brighter
sparks use the 10 kV to charge a larger capacitor string such as one rated
for Tesla coil type use or the rest of your 50 caps.
Are your 10KV capacitors meant to be operated under oil? Some of the non
ceramic ones are
A failing capacitor sounds like ssshhhhffffwwweeeeeee  BANG. Listen
carefully for this! Look for the flash, smell the burning  aaahhh....

Cheers
Peter (Tesla Downunder)


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, January 12, 2004 6:37 AM
Subject: Voltage Multiplier(4x) problems


 > Original poster: "Hydrogen18" <hydrogen18-at-hydrogen18-dot-com>
 > I just completed a 4 stage voltage multiplier made with 12 kilavolt 350 ma
 > diodes and 10 kilavolt 500 pf capacitors(dielectric). It works fine with a
 > 2500 VAC input from a mot other than a few problems. I get crackling
corona
 > everywhere and ionic force between clipleads but I was aiming for that.
 >
 > I will occasionally get arcs from the core to the primary. I'm guessing
the
 > 10 kilavolts somehow makes it way backwards and ends up somewhere on the
 > core then arcs to the primary because 120 volts looks alot like 0 when you
 > have a 10 kilavolt supply. It doesnt seem to effect anything negatively,
 > but I am concerned that the insulation may finally fail and the 120volts
 > will connect to the core. Am I right or wrong about why the core arcs to
 > the primary?
 >
 > I connected one of the 10 kilavolt capacitors(bought 50, used 8 for the
 > multiplier section) across the output of the multiplier to give me more
 > burst amperage(doubled the spark length). For some reason the leads will
 > arc over on it if I do not discharge it often enough. I'm guessing the
 > voltage builds up enough then finally arcs. What I dont understand is why
 > the heck the ones in the multiplier circuit dont also arc, it would seem
 > they should since they are exposed to 10 kilavolt stresses as well. Any
 > ideas? I am now using 20 kilavolt 500pf doorknobs without any problem.
 >
 > Another problem is trying to figure out whether the capacitors are failing
 > or not. I thought I heard one in the multiplier hissing, but it was near
 > where I had a clip lead clipped on, so I'm guessing it was corona "hiss".
 > What does a failing capacitor sound like and what are the visual
indictations?
 >
 > Thanks for any help you can provide.
 >
 >
 >
 >