On Wed, 16 Jul 2003 01:31:59 GMT, someone who calls themselves Don
Murray wrote:
"Bruce L. Bergman" wrote:
On Mon, 14 Jul 2003 02:08:02 GMT, someone who calls themselves Don
Murray wrote:
I'm surprised noone's asked about the lights you have to scroll past on my web page
to get to the transformer connections. These lights are old series street lights from
what is called an arc circuit. These were fed from a special transformer called an
RO. (regulated output) These usually put out a constant 6.6 amps or a few put out 3.3
amps. The voltage varies by the number of lights. This is done with a movable core on
a counterbalance. A characteristic of an RO transformer is when you open the circuit,
the voltage goes to the maximum, which is slightly above the primary. That's where
the term arc circuit comes from. When a light burns out the RO will go up to 5000V
and burn through the little wafer you see below the mogul base of the lamp. We still
have these in the old part of town in the 4160V area.
http://www.murrayranch.com/Electricity.htm
Just had a chance to go look - oh, /that's/ what they are... (Ever
heard of photo captions?) What was the logic behind a series circuit,
anything besides saving on wire with just one wire in a big ring?
I don't normally put photo captions on that page, as the pictures don't usually stay up
very long. I just post them for a specific discussion, or to show a friend.
I can't speak to the logic of it, they were designed before my time. I've only been in the
business 31 years, some of that stuff is nearly a hundred years old.
I suppose the wafer burns through and reconnects the circuit, and
the base for the pull-out socket has bypass contacts so you can
replace the lamp and wafer. Hot-Work Gloves Required...
That's all correct. Some other working rules on an arc circuit are you never work it hot,
but you always work it like it's hot, as it can be wrapped in the 4KV and still be
working. You never ground it, and you never open it. You put a shunt across a light when
you are working on it.
Looks like they use the same type system for the series-circuit HPS
streetlights in the Valley, with the big pole-mount RO transformers...
I've seen the whole string cycle before, probably from one lamp that's
at end-of-life and blows out, and knocks the whole string down...
All in all, I'll go for regular 120/240/277V feed Cobra-heads, thank
you. Easy to troubleshoot and repair, or swap out. And you don't
dump the whole circuit because of one bad lamp.
You want odd, I know of a trolley system where they've still got a
fully operable GE 2400VAC to 600VDC converter station running and in
service, complete with 6-phase transformer and a rotary converter, and
dump relays in case it has to scram on an overload and open the output
contactor without frying the converter windings.
That sounds interesting, I'd like to see pictures of it.
Orange Empire Railway Museum, Perris CA.
www.oerm.org I'll have to
see if I have pictures - someone should film it doing a
startup/shutdown cycle for historical purposes. Open contactors and
arc chutes, brush lifter motors...
The best part is the little worm-and-ball 'rotor wiggler' that moves
the rotor in the sleeve bearings to keep the brushes from taking a set
on the commutator, as it coasts down you can hear the ball coming off
one end and going 'plink' as it goes back to the other end of the worm
for another cycle...
And it should be good for another 100 years, as the GE Shops
completely rewound and rebuilt the rotary converter with modern
insulation a few years ago - there's a good story behind that one, it
was supposed to go in for a dip-and-bake and minor stator coil work
(with a fixed bid), and they kept digging...
It was the technician's last hurrah before he retired. :-P
-- Bruce --