By Brian Johnson and Steve Weingarth
The Arizona Cardinals are moving more than
goalposts at their new stadium; higher-tech
motor starters and drives tackle new
adversaries out West
28 INTECH DECEMBER 2008 WWW.ISA.ORG
L Motion control includes retractable roof
and retractable playing surface.
L Check the drive torque before each roof
motion; measure characteristics from the
motor at 0 Hz.
L Parallel, ﬁber-optic communications net-
work each group of eight VFDs.
s professional sports venues become big- than a traditional, clad roof.
ger and more complex in design and scale, The stadium design includes not only a retract-
architects and engineers are looking for able roof, but also a retractable playing surface.
bold new ideas. The innovative, rollout ﬁeld will save an es-
Retractable roofs have become a popular fea- timated $50 million in operating costs, as it is
ture in these structures because they provide the more economical to move the ﬁeld outside, rath-
ability to control the stadium’s interior environ- er than having the entire roof retract to allow the
ment more effectively. Minneapolis based-Uni- necessary sunshine to reach the grass.
Systems is one of a few companies that mecha- The retractable, natural-grass playing surface
nize and control these immense structures, is contained in a 16.9-million pound tray that is
which, themselves, become architectural feats. 234 ft. wide by 400 ft. long, and it is the ﬁrst of its
With its curved roof track, the Arizona Cardi- kind in North America.
nals’ project presented interesting challenges in Motor starters activate the motors that retract
designing the retractable roof mechanism. the ﬁeld. Overall, the design of the stadium is
unique enough that it has been a feature story on
Take the grass outside “The Discovery Channel.”
When the National Football League’s Arizona
Cardinals made the decision to construct a new Direct torque control
arena several years ago, the desert climate was a This roof was different from any the contractor
major consideration in the design plan. had previously constructed, according to Len-
The heat can take its toll on fans and players, nart Nielsen, Danish master electrician and se-
alike, and can be detrimental to the playing sur- nior electrical designer with Uni-Systems.
face, as well especially if it’s natural grass. On the One of the mo