ENERGY-EFFICIENT MOTORS
Energy-efficient motors, also called premium or
high- efficiency motors, are 2 to 8% more
efficient than standard motors. Motors qualify as
"energy-efficient" if they meet or exceed the
efficiency levels listed in the National Electric
Manufacturers Association's (NEMA's) MG1-
1993 publication.
Most general-purpose motors sold after October
1997 must meet the NEMA definition, according
to federal law. However, motors that exceed these
standards are readily available. Recommendations
on efficiency levels that exceed the standards can
be obtained for a given motor size from the
Consortium for Energy Efficiency.
Energy-efficient motors owe their higher
performance to key design improvements and more accurate manufacturing tolerances.
Lengthening the core and using lower-electrical-loss steel, thinner stator laminations, and more
copper in the windings reduce electrical losses. Improved bearings and a smaller, more
aerodynamic cooling fan further increase efficiency.
USE IN THE WATER/WASTEWATER TREATMENT PROCESS
Pump and blower motors account for 80 to 90% of the energy costs in water supply and
wastewater treatment facilities, and the lifetime energy costs to run a continuous-duty motor are
10 to 20 times higher than the original motor purchase price. Thus, energy-efficient motors can
play a major role in reducing facility operating costs.
Energy-efficient motors should be considered for all new installations, replacement of failed
motors, or as spares. They are frequently a cost-effective alternative to rewinding, and are
sometimes an economic substitute for well-functioning motors in high-duty applications.
However, in cases where the faster speed of the energy-efficient motor results in higher energy
use without adding to the useful work performed, the energy-efficient motor may not be an
economic option. A cost comparison will determine if a motor replacement is cost effective, and
an analysis of the whole system--including the driven process, drive train, and controls--can
reveal if other changes could provide greater benefits.
BENEFITS
Energy-efficient motors generally have longer insulation and bearing lives, lower heat output,
and less vibration. In addition, these motors are often more tolerant of overload conditions and
phase imbalance. This results in low failure rates, which has prompted most manufacturers to
