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From: Rootes(at)aol.com
>This is just a guess, but it COULD serve as an energizing circuit for the
>generator, if the generator lacks a field winding relay. It could also act
>like the "warning lamp simulator" used on later alternator equipped models
of
>both Sunbeams and Humbers, along with other Brit stuff. When current was
being
>generated, the power heated a wire inside a flasher-like device, which in
turn
>broke the contact to the warning lamp, thus extinguishing it.
>Jon Arzt Rootes(at)aol.com
I think Jon is right, the bulb puts current into the dynamo windings, and
will also
put a small magnetic field into the dynamo, where the iron is magnetized,
and
sort of acts like a periodic "polarization procedure". The iron used in the
dynamo is not very permiable, so periodic use keeps the generator internals
properly magnitized. The bulp helps would help things along.
Also, a light bulb is not exactly a resistor, it is actually an RTD, or a
resistor
with a terrible positive temperature coeficient. This is relevent to the
discussion as when the buld is dim "cold" the resistance is very low, and
the current through it and into the dynamo is high. As the bulb heats up,
and glows, the resistance goes up, and the current is reduced
proportionally.
In this way, you get to visually see a discharge condition because the
battery (feeding the bulb) is at a higher potential than the dynamo output.
Also, the buld allows a brief high current to flow to the windings, that
current limits as the bulb glows.
Jarrid Gross
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