In article ,
Vir Campestris writes:
On 02/12/2017 20:32, Andrew Gabriel wrote:
They aren't rewirable - the wire is part of the lampholder.
The wire is specially high temperature, and sometimes steal
rather than copper to cope with running continuously at high
temperature, and with very high temperature insulation.

What kind of lamp runs at nigh on 1000C to make copper care?

Copper can run up to 150C and form only protective Cu2O oxide layer
in air. At 200C and up, different copper oxides are formed which
slowly flake off, so they are not protective, but deteriorating.

Halogen lamps have to operate at a minimum bulb-wall temperature
of 250C for the halogen cycle to keep the bulb wall clean, and
normally run very much hotter than this. The lamp caps typically
run at about 350C, depending on ventilation, and they are designed
to cope with additional heating from poor lamp contacts. Copper
could be used with gas-tight connections and air-tight insulation,
but even PTFE is only good to around 260C, and glass fibre insulation
which can run hotter is not air tight. So you'll sometimes find
copper, but often something else is used instead for longer life.

--
Andrew Gabriel
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