Plasma arc failure of mains filament bulbs

[N_Cook]

Occassionaly just at the point of failure of the filament, an arc will
strike between the inlet conductors and so try and draw thousands of amps
from the mains. So knocking out triacs , fuses etc. Are there ways of
reducing this chance? orientation of the bulb? make of bulb?

 

[Adrian Tuddenham]

N_Cook <diverse@tcp.co.uk> wrote:

Occassionaly just at the point of failure of the filament, an arc will
strike between the inlet conductors and so try and draw thousands of amps
from the mains. So knocking out triacs , fuses etc. Are there ways of
reducing this chance? orientation of the bulb? make of bulb?

Philips lamps used to have fuses built into the stem to prevent an
internal arc from blowing any external fuses. The problem was that they
cost a penny or two more, so none of the retailers in my area would
stock them.

Before buyig a bulb, it should be possible to see through the neck
whether it contains just plain wires or a pair of tubular glass fuses.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

 

[spamtrap1888]

On Jul 23, 2:20 am, "N_Cook" <dive...@tcp.co.uk> wrote:

Occassionaly just at the point of failure of the filament, an arc will
strike between the inlet conductors and so try and draw thousands of amps
from the mains. So knocking out triacs , fuses etc. Are there ways of
reducing this chance? orientation of the bulb? make of bulb?

Do you buy cheapie "no-name" bulbs?

Try a Philips bulb -- at least for the US they make incandescent bulbs
with "dumet" wire inside the glass rod portion.

http://www.usa.lighting.philips.com/pwc_li/us_en/connect/tools_literature/downloads/Lighting_A_Z_FINAL.pdf

 

[Jon Elson]

N_Cook wrote:

Occassionaly just at the point of failure of the filament, an arc will
strike between the inlet conductors and so try and draw thousands of amps
from the mains. So knocking out triacs , fuses etc. Are there ways of
reducing this chance? orientation of the bulb? make of bulb?
Tungsten arc is a common failure mechanism of these bulbs.

Projection and theatrical lights have much heavier filaments and
so the problem is a lot worse. There's not a whole lot that can
be done about it, and certainly bulb orientation won't have any
effect.

Fuses? This is exactly what fuses are FOR, to remove current to shorts!
Properly designed and sized triac dimmers should survive at least a few
of these incidents, but cheap dimmers are probably designed to only
survive the normal load current. A fuse fast enough to protect the dimmer
will probably cost MORE than the dimmer, but they are available.

Jon