Path: utzoo!attcan!uunet!ncrlnk!ncrcae!ece-csc!ncsuvx!gatech!rutgers!iuvax!silver!commgrp
From: commgrp@silver.bacs.indiana.edu
Newsgroups: sci.electronics
Subject: History-- series streetlamps
Message-ID: <7200013@silver>
Date: 29 Sep 88 19:56:00 GMT
Organization: Indiana University CSCI, Bloomington
Lines: 22
Nf-ID: #N:silver:7200013:000:737
Nf-From: silver.bacs.indiana.edu!commgrp    Sep 29 14:56:00 1988



History-- series streetlamps


Old-style incandescent streetlamps were wired in series.  I always 
wondered how such a system could work. I finally learned the method 
which kept the lights on when a bulb burned out:

One hundred 120-v bulbs were wired in series and connected to a 12,000 
volt line.  Above each lamp socket was a pair of spring-loaded 
contacts separated by a piece of waxed paper.  If one bulb burns out, 
the voltage goes up, the paper arcs through and burns away, forming a 
short circuit.  The remaining bulbs get 1% more voltage.  This 
ingenious method saved wire, transformers and switches.  The 
maintenance crew had to be diligent and not let too many bulbs burn 
out!

--

Frank
reid@gold.bacs.indiana.edu