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G8MNY > TECH 30.04.15 10:21l 72 Lines 3117 Bytes #999 (0) @ WW
BID : 28863_GB7CIP
Read: GUEST
Subj: A ton per cell battery
Path: IW8PGT<IW7BFZ<I3XTY<I0OJJ<GB7CIP
Sent: 150430/0612Z @:GB7CIP.#32.GBR.EURO #:28863 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (New Nov 08)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
When I was an telephone engineering apprentice in the 60's I had to work on the
Croydon telephone exchange battery. These were some of the biggest in the UK,
weighing in at about 1 ton per cell!
There was no backup generator on site, as the site was next to Croydon's main
water well & any diesel oil spillage could be dangerous. (in 1952 there was
water contamination!) So the batteries had to do at last 24 hours & handle a
peak load of 1100 Amps (50V) for the 4 very busy 10,000 line Strowger telephone
exchanges, so the total battery capacity was over 20000 AH (10000/battery).
The 2x 25 cell 50V battery sets (25 was unusual & gave a good 50-54V) came to
100 tons, plus 2x 1000 Amp charging rectifier bays (silicon diodes!), this lot
was on the ground floor for obvious reason. From memory the cells were
something like this..
< ---- 1m ---- >
Acid __Cell Plates__ Lead
Level-³±±ÝºÅºÅºÅºÅºÞ±±³^ lined
Woodenٱݺ³º³º³º³ºÞ± | cell Each cell was about 1m x 1m & 1.5m tall
sides -±Ýº³º³º³º³ºÞ± | case open top construction type, made from
±Ýº³º³º³º³ºÞ± | wood outer shell lined with lead. My
±Ýº³º³º³º³ºÞ± 1.5m job for 1 day (done once per week) was
±Ýº³º³º³º³ºÞ± | to top up all the cells (50 gal cell?)
±Ýº³º³º³º³ºÞ± | with tap water from a hose, (Croydon's
±ÛÜÜÜÜÜÜÜÜÜÛ± | hard tap water was OK for this).
±±±±±±±±±±±±± |
± PLINTH ± v
As well as topping up, 1 cell was de-scaled per week too, This was done by
removing the glass splash guards on top & inserting a board between each plate
to dislodge any whisker growths between plates. (dust coats, gloves & eye
shields was essential).
POWER SYSTEM
ÚÄÄÄ¿ fuse ÚÄÄÄÄ¿
³PS1ÃÄÂ---Âo-oÄÂÄ´Bat1³
ÀÄÄÄÙ \ / / ÀÄÄÄÄÙ Huge
X ÃÄÄÄÄÄÄÄÄÄExchange
ÚÄÄÄ¿ / \ / ÚÄÄÄÄ¿ Bus bars
³PS2ÃÄÁ---Áo-oÄÁÄ´Bat2³
ÀÄÄÄÙ fuse ÀÄÄÄÄÙ
The manual large copper knife switching, enabled either PS rectifier sets to be
connected to either battery & either or both batteries to be connected to the
load. The high DC currents were measured by new hall effect devices.
Each rectifier set had a motor driven 3 phase choke feeding an isolation
transformer. The secondary I think fed a 12 phase silicon bridge rectifier to
the output. Some fused filtering caps were put across the output to remove the
last of the 600Hz hum.
No battery room fuses were used on the main bus bar, as this was considered to
dangerous to loose the whole lot.
Distribution fuses were used on each section in the building, but there were a
few arc marks in the 4 story building were bus-bar accidents had happened! Up
to 1V bus bar drop was allowed to the furthest point in the building, & even
with thick copper & huge main ally feeds the bus bars still ran warm!
See my Tech bul on "AC 3 Phase Power"
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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