Newsgroups: alt.engineering.electrical
Subject: Re: Washing machine 240, 50Hz - 240, 60 Hz?
References:   <[email protected]>  <[email protected]>  <[email protected]>      <[email protected]> 
[email protected] writes:

> On 11 Nov 2006 19:40:15 GMT Andrew Gabriel  wrote:
> | In article ,
> |        [email protected] writes:
> |> That would work for the constant current series lights.  But what about the
> |> Christmas light series strings?
> | 
> | They work the same way. There's a piece of wire wrapped around
> | the lead-in wires which has a layer of thin insulation, which
> | breaks down when mains voltage appears across the lamp.
> | 
> | The circuit is not constant current, so the loss of a lamp
> | increases the power of the remaining lamps, and reduces
> | their life. This can create a run-away effect as more die
> | and the remaining ones burn at higher power. There's normally
> | a fuse lamp in the set, which is a lamp which does not short
> | out when it dies. This is to prevent a few lamps running at
> | excessive power and igniting the Christmas tree, or the whole
> | set shorting out. In the UK, we do get typically a couple of
> | house fires a year caused by Christmas trees, and this maybe
> | when people have replaced the fuse lamp with a shorting lamp.
> 
> It's that increasing current I was wondering about.
> 
> But you guys have actual fuses in your plugs.  Why not set that fuse to
> a bit above the proper current?  Of course someone will end up replacing
> the fuse with one of the wrong value.

In Finland I have owned several cristmas lights that have not had 
any fuse in the plug, but another type of protection: one of the 
bulbs on the christmas light is special "fuse bulb" that does 
not have that piece of wire wrapped around the lead-in wires. 
That bulb is clearly marked and instructions say that this bulb 
should be only replaced with the exactly same type bulb.  
 
> This made me think of a scenerio I described to someone once.  The scenario
> is wiring up 60 light bulbs of our 120 volt variety in series and powering
> it from a 7200 volt MV source.  Then wait for one to burn out, or force one
> to somehow, or just have one already burned out with a small filament gap.
> Then stand back and watch it all explode.
> 
> -- 
> |---------------------------------------/----------------------------------|
> | Phil Howard KA9WGN (ka9wgn.ham.org)  /  Do not send to the address below |
> | first name lower case at ipal.net   /  [email protected] |
> |------------------------------------/-------------------------------------|

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
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