Re: RE: Bleeder Resistors

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: DRIEBEN@xxxxxxxxxxxxxxx 

Hi all,

In a way, I agree with both sides of this argument ;^)
If you are using a single unit commercial pulse capa-
citor in a typical AC powered Tesla coil (except for
an equa-drive configuration), then the primary coil
and secondary winding of the power transformer will
quickly bleed off the residual charge of the capacitor
after the power is shut down.
With multiple seriesed capacitors, like MMCs,  each
individual capacitor in the string can indeed hold some
residual charge and I would agree that each of the indi-
vidual caps need to have their own bleeder resistor in this
configuration. However, Gary also brings up a good point that
I had not originally considered with the "worst case scenario"
-like the transformer's secondary winding fails open
circuit or the primary tap happens to come loose while
the coil is powered up. Of course, the latter primary
tap scenario would be almost impossible in my big coil
setup as I have the tap clamped and bolted into the tap
position on the primary coil. Also, I would say that the
chances of my 15 kVA pole pig's high voltage winding
failing open circuit during coil operation are rather
slim. However, just in case the "impossible" does happen,
bleeder resistors are the best insurance policy. I suppose
it's a matter of how much of a risk factor that you're
willing to accept. Every coiler accepts a certain degree
of risk by the mere fact that they decide to build and
operate  Tesla coils, which are inherently dangerous, in
the first place. "I" personally don't use bleeders on my
coil setup and like Dr. R, I've never gotten a nasty sur-
prise from the primary capacitor after shutting down the
power to the coil in my AC powered system. Now with a DC
or equa-drive system, that's a very differnet story indeed
and the risk of a dangerous shock would be VERY HIGH if
the primary circuit components are handled after power-down
without employing definite measures to insure that the
capacitor(s) is/are fully discharged first!

David Rieben

----- Original Message -----
From: Tesla list <tesla@xxxxxxxxxx>
Date: Monday, January 2, 2006 6:13 pm
Subject: RE: Bleeder Resistors

> Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>
>
> With spark gap coils, with the coil off and the gap being an open
> circuit, the tank cap, primary coil, and NST secondary form a
> loop, and
> any charge in the cap is discharged essentially immediately
> through the
> primary and NST.  But I disagree with the good Dr about a bleeder
> beingunnecessary.  They're unnecessary the same way seat belts are
> unnecessary.  Should the primary tap connection or NST secondary
> connection come loose, the discharge path is lost.  In my early
> coilingdays I once tried to determine the best primary tap point
> by dragging
> the tap connection across the primary turns, while it was operating.
> The arcing between the tap wire and the primary was fierce and I
> abandoned that idea immediately.  But I quit with the tap
> disconnected.When I shut off the power and attempted to make the
> tap connection, I
> got a very stiff ZAP, and I was lucky that the cap didn't carry a
> largercharge.
>
> In short, "stuff" happens, and having a backup discharge path
> (bleeder)in place is cheap insurance.  You won't be able to find a
> singleoff-the-shelf resistor at a reasonable price capable of the
> job, but one
> can easily build a series array that will withstand the voltage.  The
> resistance value is not critical; probably anything between 50-100
Meg
> is OK.  I made an array of 39 2Meg 1/4W resistors, 'cause that's
> what I
> had available.  See photo about half way down on my RSG page:
> http://www.laushaus.com/tesla/sync_gap.htm
>
> Regards, Gary Lau
> MA, USA
>
>
> Original poster: Just Justin <rocketfuel@xxxxxxxxxxxxx>
>
> Can someone explain to me why this is not necessary?
>
> I don't see why the tank cap seems to always be 'empty' (haven't
> actually
> measured voltage for fear of zapping another meter) after a run.
> If the
> car was raised to almost-breakdown in the spark gap, shouldn't it
stay
> charged some of the times?
>
> Justin
>
>
>  > Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
>  >
>  >
>  >
>  >
>  > Bleeder resistor is not necessary unless you are running DC on
> thiscap.
>  >
>  > Dr. Resonance