RE: Bleeder Resistors

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

I hope your wife hasn't recently taken out a substantial life insurance
policy on you...

1) Let's do the math.  Assuming you have a 15/60 NST, peak voltage is
about 21kV.  21kV across 1KOhm will draw 21 Amps.  But you have only a
.06A transformer.  Nope, no good.  I suggest something between 50 and
100 MegOhms.  A 50Meg bleeder will draw 0.42mA peak.

2) A dead short will discharge any cap to zero in a matter of
microseconds.  All you need to do is ensure that you've made proper
contact with both terminals, and you're done.  I figure that I have two
discharge mechanisms in place - the normal path through the NST
secondary and primary coil, and my bleeder resistor.  The chances of
either one failing is small but not zero.  But the chances of BOTH
mechanisms failing are so remote that I don't use a hot stick.

3) Industrial equipment often had safety lockout switches that turn
power off during servicing.  This prevents accidental turn on by others
without the key.  But for our purposes, just pulling the plug out of the
wall is probably the best thing.  It's clear when the plug is lying on
the floor, but not so clear which position a lockout switch is in.

4) I suppose you could, although the hazard of a cap charged to 120-160V
pales in comparison to the tank cap hazard.  Also, PFC caps are normally
permanently wired in parallel with the NST primary, which would
immediately discharge the cap when power is off.  But then I'm the guy
that disconnected his primary tap and got zapped...

Regards, Gary Lau
MA, USA

> Original poster: otmaskin5@xxxxxxx
>
> My wife said don't worry, I don't need bleeder resistors.  But having
> read all your advice on this topic, now I'm a little suspicious of
> her motives.  Thanks for your help.  I do have a couple of other
questions...
>
> 1.  I have two wire wound power resistors (50W, 1KOhms) not being
> used.  Would one or both of these make a suitable bleeder resistor
> for my .03uF 35,000v Maxwell cap?
>
> 2. I'm hearing, even with bleeder resistors, hot sticking to
> discharge the cap is still adviseable.  I have been holding a stiff
> wire (taped to a length of PVC) accross the Maxwell's 2 terminals for
> 5 or 6 seconds.  Is that sufficient discharge procedure?
>
> 3. One of the responses also recommended "locking it out."  Can
> someone explain what this means?
>
> 4. I also have PFC caps on my coil.  I assume these also need to be
> discharged?  Same procedure as with tank caps, right?  Would you use
> bleeder resistors on PFC (motor run) caps?
>
> Thx, Dennis Hopkinton, MA
>