Hi Elvis
On (22 Jul 96) Elvis Hargrove wrote to Alec Cameron...
-> was done with high powered versions, great howling monsters running
-> at about 20volts, 20 000 amps. Brown Boveri *I think* made these.
 EH> Great googly wooglies, Alec!  That's some huge rectifier!  What
 EH> frequency did it run?  Didn't the rectifier contacts take a beating?
50 cycles, three or six phase. I *imagine* that the contacts were carbon and
that the synchronising was such that overlap, put most of the sparking on the
transformer primary circuit, the LV side contacts moving at zero current.
B Boveri also supply the railroad 1500v dc steel tank pumped rectifiers in 
he
same city. We were required to work inside these at major overhauls, "in
stockinged feet" in order to minimise dirt ingress.
 EH> We have similar instruments in use in the oil patch and along the miles
 EH> and miles of natural gas transmission pipelines.  Also lots of
 EH> sacrificial anode power supplies run off the power mains with stepdown
 EH> transformers and silicon rectifiers now.
Here we would run rectifier controlled contactors to close "bonds" between 
he
rail track and the structure to be protected. The orientation and location,
was chosen so that the structure would then be forced to a negative potential
to soil. Of course this caused the rails to corrode! but that was acceptable.
 EH> Lord, Alec.  You aint as old as I thought. The ones I'm talking about
 EH> were in the late 30's and early 40's cars.  NO transistors of course and
 EH> the 6 volt tubes drew about 7 amps of heater current, plus whatever the
 EH> vibrator and B+ system required. (Normally about 250 Vdc @ 3-500 ma.)
Here, auto radios were a novelty until about 1946. The synch and asynch
vibrators, were standard then.
 EH> The other thing is too gross to consider!  I'd just as soon never have
 EH> KNOWN about it!  
Well, that's how med science progresses and without those gross
experiments lotsa us would have fallen off our perches years ago.
Cheers.....ALEC
... ........BUNDANOON, on a dirt track leading to the Info Superhighway
--- PPoint 1.92
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