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"New
horses in the efficiency derby"
With
trilingual summary
We think
of a global marketplace as one in which the same goods, made to the same
standards, are sold worldwide. Although that applies to many consumer goods, the
approach to efficiency standards for industrial electric motors is broadly
diverse. Government agencies and environmental groups issue an increasing
variety of requirements.
Improving
motor efficiency is simple in theory. What's uncertain is how far such
improvement can cost-effectively go. That depends upon the economics of
manufacturing and energy sources in each country. Within the European Union,
several agencies now prescribe motor efficiency levels, among them CEMEP (a
motor manufacturer group) and the SEEEM program sponsored by utility,
government, and industry organizations. Elsewhere, standards in China, Japan,
Australia, the United States, and Canada have been adopted to dictate
efficiencies at several levels or grades, for standard machines, mostly of low
voltage ratings at 2, 4, and 6 pole speeds (sometimes including 8 poles).
Some
requirements are guidelines only; others are subject to legal enforcement. In
either event, motor users must be able to rely on the accuracy of the
manufacturer's stated efficiency when making purchasing decisions.
Unfortunately, little progress has been made towards a single universally
accepted global standard for verifying motor efficiency by test.
The
problem is stray load loss. No simple test measures it directly. In the United
States, load testing plus statistical analysis using IEEE Standard 112 Method B
has been incorporated into federal law. In Europe, under IEC 60034-2, stray loss
has been arbitrarily assigned a single fixed percentage of power input for all
motor ratings. However, IEC 61972 was recently adopted to allow either the
method of IEEE 112, or a varying percentage of output, and IEC 60034-2 is now
being revised to add yet another option for stray loss evaluation. In some
countries, prescribed efficiencies depend upon which test is used.
Add to
that the accommodation for both 50 Hz and 60 Hz designs, plus the widespread
system of output rating in kilowatts instead of horsepower, and the motor user
clearly faces increasing difficulty in deciding what to believe. No simple
solution appears to be forthcoming soon.
From “New
horses in the efficiency derby,"
to be published in the
Electrical Apparatus September 2007 issue
. Visit our online webstore to
order
copies. © 2007
Barks Publications, Inc. All Rights Reserved.
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