IEEE Power & Energy Magazine - May/June 2014 - 8

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editor in chief, molken@ieee.org. Letters may be edited for publication.

Motor-Generator Sets
for ac to dc Conversion

In his "History" article "the Rotary era,
Part 2" that appeared in the november/
december 2013 issue of IEEE Power
& Energy Magazine
(vol. 11, no. 6, pp.
96-105), tom Blalock
stated that the reason
that Bethlehem steel
chose to use motorgenerator sets in certain locations rather
than rotary converters was not known.
I hope I am able to
shed some light on
that choice.
I worked in a portion of the Inland steel
company's Indiana
Harbor Works, a facility now known as the
acelor-Mittal Indiana
Harbor Works-east. I
worked in both the #2
blooming mill (constructed about 1916)
and the #2a blooming mill (constructed
about 1964). Both mills were two-high reversing rolling mills. the #2 bloomer was

driven by a dual-armature dc motor,
which in turn was powered by a motorgenerator set that consisted of a single
6,000 hp, 25-Hz, 2,200-V induction motor,
which was direct connected to two dc
generators and a flywheel. this equipment (Westinghouse) was later upgraded
to 7,000 hp by improving the temperature
rating of the winding insulation. If my
memory serves me right, the rated r/min
of the induction motor was 300.
the mill stand driven by the dc motor would be placed
under a very sudden and heavy load
by the introduction
of an ingot between
the rolls and would
then have the load
drop off just as precipitously when the
other end of the ingot dropped out after
rolling. the rotation
of the dc motor and
mill stand was then
quickly reversed (no
mean trick since the
double-winding  armature alone weighed
over 90 tons) and the
rolling and reversing process repeated
several times. From
this description, plus
noting the inclusion of a flywheel, it is
evident that the added rotating mass of
the separate motor and generators was
not a liability but an asset and probably
the primary motivation for using the separate electric machines.

It was interesting
to see a single
installation that
included both
a "last hurrah"
motor-generator
installation and
one of the first
high-power
electronic
control systems
side by side.

Digital Object Identifier 10.1109/MPE.2014.2301562
Date of publication: 17 April 2014

8

ieee power & energy magazine

the #2a bloomer, constructed roughly 50 years later, incorporated many of
the same features, right down to the motor-generator set with double generators
and a flywheel. the motor, of course,
was now a 60-Hz machine, and improvements in the controls allowed for
the use of separate 4,000 hp dc motors
to individually drive the mill stand's two
rolls. the #2a bloomer was a general
electric (ge) plant. this mill's load profile was very similar to #2's, and the two
stands operated together, with the #2a
mill further processing steel from #2 for
certain products, until #2 was razed in
1991. to my knowledge, #2a bloomer
remains in service today.
Interestingly, the 21-in mill, which
rolls steel produced from #2a bloomer,
was one of the first solid-state rolling
mills. Installed at the same time as the
#2a bloomer, it consisted of eight roll
stands of 3,000 hp each. It was a ge
system; silcomatic is the brand name
that comes to mind, but my recall may
not be accurate. It was interesting to
see a single installation that included
both a "last hurrah" motor-generator
installation and one of the first highpower electronic control systems side
by side.
I hope that this helps.
-David E. Mertz

Author's Response
I greatly appreciate the comments from
david Mertz regarding the use of flywheel motor-generator sets for rolling
mills at Inland steel and especially
the simultaneous installation of such
may/june 2014



Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - May/June 2014

IEEE Power & Energy Magazine - May/June 2014 - Cover1
IEEE Power & Energy Magazine - May/June 2014 - Cover2
IEEE Power & Energy Magazine - May/June 2014 - 1
IEEE Power & Energy Magazine - May/June 2014 - 2
IEEE Power & Energy Magazine - May/June 2014 - 3
IEEE Power & Energy Magazine - May/June 2014 - 4
IEEE Power & Energy Magazine - May/June 2014 - 5
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IEEE Power & Energy Magazine - May/June 2014 - 128
IEEE Power & Energy Magazine - May/June 2014 - Cover3
IEEE Power & Energy Magazine - May/June 2014 - Cover4
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