THE AEMT ENSURES ENERGY
EFFICIENCY IS MAINTAINED
DURING SERVICE AND REPAIR
n extensive joint research
project conducted at the
University of Nottingham
found that energy efficient
motors remained within
plus or minus 0.5% of their original
efficiency after being repaired by a
good service centre. This is within the
specification tolerances of the label
and efficiency banding. These tests
were backed by a number of leading
international industrial organisations
and Government Departments in the UK
and USA. Tim Marks of the Association of
Electrical and Mechanical Trades (AEMT)
reviews the projects and their findings.
A
Sometime ago, members of the AEMT and
the American Association EASA worked
together to establish "The Good Practice
Guide to Maintain Motor Efficiency" after
repair. The Good Practice Guide has since
been used by members of the AEMT
and EASA internationally to ensure that
any repairs carried out retain their rated
efficiency.
The Good Practice Guide and research
details are freely available from the AEMT
Website.
The first Best Practice Guide to maintain
Energy Efficiency was produced by the
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AEMT in conjunction with Department
of the Environment, Best Practice
Programme on Energy Efficiency. It was
led by Professor David Walters, who had
previously led the Brook Crompton design
team on their ground breaking W range of
energy efficient motors.
The project remains the largest study of
its kind with tests being carried out on 34
electric motors. These were 5.5 kW D132S
machines supplied by manufacturers.
They included 13 old design aluminium
motors, 13 original design "Energy
Efficient" motors, and 8 "higher efficiency"
motors. A major difference between the
machines was the quality of their stator
laminations. The "Higher Energy Efficient"
machines were some of the first to use a
high grade steel coated with an inorga nic
based L3 film.
This heat resistant varnish film increased
the ability of motors to withstand
annealing temperatures, and withstand
multiple burn out temperatures without
any detriment to the core laminations,
as shown by tests during the project.
Improvements in the electrical steels
using L3 or better have formed the basis
of new energy efficient machines over
the past 20 years. This is shown in figure 1
extracted from the original project.
A few years later the original research
programme was expanded to include
larger machines up to 225 kW. Several
Government Departments, electro-
technical companies and industry groups
- both domestic and international - were
approached to join a wide-ranging
project to broaden the base of the next
research project.
Sufficient machines were included to
give statistically reliable results, which
increased the cost of the exercise.
To mitigate this, the AEMT invited
representatives of the US Department of
Energy and through them the US repair
trade association (EASA), both of whom
agreed to join the project.
The AEMT then approached their own
national government for support and
further sponsors were encouraged to join.
The final list of participating organisations
was impressive, and included the UK
Energy Efficient Best Practice Program,
UK Ministry of Defence (Navy), UK Water
Industry Research Centre, and British
Nuclear Fuels.
Ten motor manufacturers also became
partners to the project providing motors,
technical data, and assistance for the
study. These included ABB, Siemens,