Energy for Sustainable Development
The Journal of the International
Energy Initiative
© 2007, International Energy Initiative, Inc.
ISSN: 0973-0826
Volume XII, No.2, June 2008, pp. 78-87
A novel
efficiency improvement measure in three-phase induction
motors, its conservation potential and economic analysis
V. Prakash, S. Baskar, S. Sivakumar, and K. Sri Krishna
Abstract
This paper
performs end-use energy analysis and estimates the benefits to
India of a proposed efficiency improvement measure in
three-phase induction motors. It was found that in a 3.7 kW
motor, widely used in agriculture and industry, typical
rewinding practice is associated with reduction in either
winding conductor size by 1 SWG or reduction in number of
turns per coil by one turn from the winding specification.
This improper rewinding practice results in efficiency
reduction by over 5 percentage points. Moreover, torque per
ampere is decreased and higher temperature rise ensues. This
is applicable to motors of all efficiency categories including
energy-efficient designs. A method has been proposed to
non-destructively determine the winding details without
damaging the winding. This paper proposes a measure for
efficiency improvement in improperly rewound motors of
“standard” and energy-efficient designs as well as on
“standard” motors that have not been rewound. The efficiency
improvement measure essentially involves rewinding the motor
taken up for efficiency improvement. The reduction in
efficiency due to not-so-proper rewinding practices is also
taken into account for the analysis. By means of this measure,
the aforementioned performance deterioration can be reduced,
if not removed entirely. The method will be of significance to
India, where more than 50 % of the operational motors are
rewound motors and the majority of the rewinders are not well
informed. Best practices to be followed during rewinding are
also recommended. The conservation potential of the measure
has been explored and economic analysis for implementation of
the measure is provided. The payback period for the investment
towards the proposed efficiency improvement measure by the
industrial end-user for the 3.7 kW (5 HP) case is 1.3 years,
if the motor is to operate for 24 hours continuously for 300
days. Suggestions have been made for the implementation of the
efficiency improvement measure on an all-India level.
Key-words:
electric motor, efficiency, non-destructive testing, rewound
motor, three-phase induction motor
