Why is the electric motor important
Why is electric motor efficiency so important?
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in this module we will explain the
importance of high motor efficiency we
will also take a trip inside an electric
motor to find out what we mean by
efficiency and explain the losses that
occur within the motor that contribute
to its efficiency rating the world is
facing a serious energy challenge demand
for electricity will grow faster than
for any other form of final energy
pressures to reduce energy consumption
and lower carbon dioxide emissions come
from everywhere the simplest way to
address this challenge is to seize the
opportunities for energy reduction that
come from using energy more efficiently
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over 40% of generated electricity is
consumed by industry and two-thirds of
that energy is used by electric motors
by increasing efficiency using more
efficient motors it would be possible to
realize huge savings in both energy and
carbon dioxide emissions this has
prompted governments to introduce MEPs
minimum energy performance standards
setting mandatory minimum efficiency
levels for electric motors so what is
motor efficiency efficiency is simply
the ratio of output power to input power
and presented as a percentage let's take
a standard motor with a 75 kilowatt
output achieving this output requires a
power input of 80 point nine kilowatts
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using our formula we get an efficiency
of ninety two point seven percent this
also means that the power losses amount
to five point nine kilowatts so where do
these losses come from and how can they
be minimized to increase the motors
efficiency we will try to explain that
in a simplified way
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the no load losses shown here are almost
constant regardless of the motor load
stator iron losses are present due to
the energy required to magnetize the
core material and includes losses due to
the creation of eddy currents that flow
in the core they can be decreased by
using better and thinner electromagnetic
steel and lengthening the iron core
friction losses are present due to the
friction in bearings and sharp seals and
can be reduced by correct dimensioning
and selection of bearings windage losses
are caused by air resistance in the fans
and can be reduced by optimized fan and
airflow design after the no load losses
we have the load losses and here there
are three types stator winding losses or
I squared R losses are present due to
the current flow through the resistance
of state of winding they can be reduced
by optimizing status slot design with
the windings tightly packed to ensure a
good slot filling ratio together with an
optimized iron core to maximize the
strength of the magnetic field rotor
losses the rotor also suffers I squared
R losses caused by the rotor currents as
well as iron losses caused by the
magnetic flux interacting with the rotor
core
they can be reduced by increasing the
size of conductive bars and end rings to
produce low resistance additional load
losses or stray load losses are present
due to the leakage flux caused by
variations in the windings mechanical
imperfections in the air gap and
irregularities in the air gap flux
density they can be reduced by improving
slot geometry and minimizing deviation
in the air gap
unfortunately losses are an inevitable
part of running a motor and since they
directly affect the efficiency
manufacturers of premium motors do their
very best to reduce them by using higher
quality materials cutting-edge motor
designs and manufacturing in
high-precision automated factories
losses are kept to a minimum this means
that with every successive generation of
motor design efficiency gets improved
and contributes to solving part of the
global energy challenge in the next
module we will look at the cost of
ownership and provide a few tips on how
this can be reduced
