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"A
New Standard for Large Drives"
With
trilingual summary
The
energy-saving and operating flexibility benefits of electronic adjustable-speed
control of a-c motors have brought users inconveniences as well. Some can be
serious problems with medium-voltage apparatus in sizes above a few hundred
kilowatts.
First,
premature equipment failures can cripple a continuous process industry. Second,
advances in complex electronic technology can render both hardware and software
obsolete within a few years. Replacement parts for older units become difficult
to get. The retraining and re-programming needed for the transition to newer
apparatus can cause costly downtime.
Seven
years ago, petrochemical engineers within the IEEE decided that a standard was
needed to enable drive purchasers to deal with such concerns. The result,
published in 2006, is IEEE Standard 1566 for "Performance of Adjustable Speed AC
Drives Rated 375 kW and Larger," and covering only ratings of 750 volts and
above. The scope involves the entire drive system consisting of switchgear,
input transformer if any, controls, bypass, and motor (either induction or
synchronous). Compatibility between drive and motor is assured by vesting total
system responsibility in a single vendor.
While
placing no restrictions on basic drive topology, the standard presents detailed
requirements for drive enclosure (such as the ability to contain a bolted
fault); installation; grounding and bonding; solid-state component ratings and
cooling; loading capability; harmonic generation; behavior during utility supply
disturbances including voltage sags, swells, and transient surges; control,
alarm, and protective functions; testing; startup; and safety.
In
addition, IEEE 1566 stresses the need for reliability, and dictates minimum
service life. The vendor must identify those replacement parts needed to
maintain that life, make adequate technical support available throughout that
life, and must furnish expected values of mean time between failures and mean
time to repair "based on known experience."
Appended
to the text are data sheets allowing both purchaser and vendor to describe any
changes or variations specific to a particular application.
From “A
New Standard for Large Drives,"
in the
Electrical Apparatus October 2007 issue
. Visit our online webstore to
order
copies. © 2007
Barks Publications, Inc. All Rights Reserved.
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