[CrackMonkey] [gkm@petting-zoo.net: Motors.]

Nick Moffitt nick at zork.net
Wed Apr 18 18:23:58 PDT 2001


----- Forwarded message from glen mccready <gkm at petting-zoo.net> -----

[damn.  maybe electric cars won't suck afterall... -gkm]

Forwarded-by: Nev Dull <nev at sleepycat.com>
From: "Mike O'Dell" <mo at ccr.org>

Speaking of stories...

My dad worked for Oklahoma Gas and Electric for 40 years and there's an
oil refinery in my home town.  There's a thing central to a refinery
called a "catalytic cracker" in which long tarry chains of hydrocarbons
are "cracked" into shorter gassy chains.  This requires a lot of heat,
steam, and air.  the air is provided by a blower -- a *big* blower, run
by an electric motor.  This motor is a synchronous induction motor and
is a mere 40,000 horsepower.  When the motor is running (i.e.,
synchronized) the power requirements aren't that astounding.  when you
*start* the motor, though, it's an altogether different matter.  (The
"locked rotor" stall current is just incredible.) Luckly you do this
very rarely -- the catalytic converter runs all the time, and the only
time the blower is "off" is when the converter is being rebuilt
(actually if you turn the blower off, you *will* get to rebuild the
converter, assuming it doesn't explode).

Anyway, the big cracker in this refinery had been down for a year
getting the inner lining replaced and it came time to restart the big
blower.  It took about 6 months of planning and preparation to do this.
OG&E's entire transmission grid was specially configured for this event.
Not only was everything available up and spinning, but there was a
specific load-flow distribution established before the startup.  It was
scheduled for about 3am local time, and two semi-trailers full of *very*
big capacitors were brought in (with some non-trivial switch gear) to
parallel the motor and balance the inductive load with an equal
capacitive load.  When the motor was coming up, the capacitors were
switched out incrementally to keep the power-factor in line.

The biggest part of the show was the "starter pony" -- a 4,000
horsepower deisel engine used to get the motor and fan rolling along
before hitting the switch (to avoid a "locked rotor" stall current
inrush).

Anyway, for the main event, the load-flow engineers at OG&E's
headquarters were all in the operations center with the damage
containment plans ready to go if Something Bad Happened.  the start-up
went according to plan, and the entire transmission network sloshed
("ringing" in the technical sense) for almost 8 hours afterwards.

Now *that* is what i call a motor!

	-mo


----- End forwarded message -----

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