Why is electric motor efficiency so important?



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


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


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


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


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