seminar fianle

Energy scenario and efficiency in electric motors…
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1. BACKGROUND/INTRODUCTION
The production side of business activity is referred as industry. It is a business activity,
which is related to the raising, producing, processing or manufacturing of products. Industrial
production represents a small but growing segment of economic activity in Nepal and most
industries are small, localized operations based on the processing of agricultural
products. Most of the Nepalese industries are of manufacturing type, and fulfills the need of
consumers by producing the goods that are sufficient for the domestic market. Only
multinational companies and some of domestic companies works out for international market.
Whether the industry is of service type or the manufacturing type, use of energy is a must for
its operation. In context of Nepal it is found that the basic sources of energy for these
industries are fuel wood, agricultural residue, animal dung, petroleum products, coal,
electricity, biogas, micro-hydro and solar power among which the fuel wood is the most
widely used one. And the form in which these energy are used is mostly the electrical energy.
Its consumption pattern is explained in the other parts of this seminar paper. In today’s world
the word ENERGY is a hot cake, its crisis is heading rapidly. In this context Nepalese
industry can also contribute towards the global energy saving by realizing and implementing
the proper way of using energy.
Secondly, after knowing about the fact that electrical energy is mostly used energy in the
Nepalese industry, the focus of this paper turns to energy efficiency in electric motors. We
can easily observe that electric motors are the prime mover of the industries without which
almost no any machine can be operated. And use of inefficient and very old motors have
rapidly increased the energy losses and wealth loss in the industry. As electric motor play
vital role in saving energy ( saving energy is producing energy) this paper also focuses on the
assessment of energy losses in motors and energy efficiency opportunities .
From the very beginning part of this report it reflects the major forms and sources of
energy being used by Nepalese industries along with its availability and forecast. There are
different manufacturing industries located in the different parts of the country. The
government in assistance of various energy efficiency international and national projects
should implement the well amended and people friendly industrial policies for the better
operation of these industries. Considering electric motors as the prime mover in any type of
manufacturing industry, this seminar paper is secondarily focused on the leakage/losses of
energy in electric motors; an appropriate way of assessing energy opportunities in motors and
the keypoints to improve life and working efficiency of motors.
Keywords: energy efficiency, Nepalese Industry, induction motors, power factor

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2. OBJECTIVE OF THE TOPIC
Energy efficiency and energy conservation are very closely related to each other. With
increase in demand of energy and due to uncertainties in oil supply and fluctuating price of
conventional fuels, efficiency and conservation of energy has become an important aspect of
industrial as well as rural development. A large amount of electrical energy is consumed by
induction motor used for irrigation in rural sector and industrial purpose in urban sector. In
this context, the main objective of this seminar paper is to aware the local people and
industrialists about the current energy consumption scenario among Nepalese industry. With
reference to the data available in different books and journals I have explained what kind of
energy sources are widely being used in Nepalese industries, what form of energy is mostly
used, how much dependent is our domestic industry in the energy and where the nation is
lagging. Nepal being 2nd
richest source of water in the world has huge potential to produce
hydropower/ electricity for the proper running of industries and meeting the energy
requirement of the nation. But the irony is our country is not working on it, may it be the
interference of political issues or lack of awareness among we Nepalese. So through this
seminar I would like to focus the reader’s attention on efficient consumption of energy in the
country. Secondly the report has worked out for assessing electric motor’s energy
consumption and losses and the possible saving areas of obtaining energy efficiency.
Through this seminar paper I have explained the working mechanism of electric motors
(especially the induction motor) along with the details of its parts so that the reader
understands motor clearly. After understanding the electric motor very well the industrialists
and related personnel’s are expected to use it efficiently and reduce the energy loss by such
motors.

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3. LITERATURE REVIEW
3.1 TYPES OF NEPALESE INDUSTRIES:
Based upon the fixed assets by the Industrial Enterprises Act 1992:
S.
N
Industries (Scale) Fixed Asset
1 Small Up to NRs. 30 million
2 Medium Between NRs. 30 million and 100 million
3 Large More than NRs. 100 million
Based upon the Categories by the Industrial Enterprises Act 1992:
1.
Manufacturing
2. Energy
Based
3. Agro & Forest 4. Mineral
5. Tourism 6. Service 7. Construction 8. Cottage

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3.2 MAIN MANUFACTURING INDUSTRY DISTRIBUTION IN
THE COUNTRY
The industrial sector in Nepal is underdeveloped compared to the developed part of the
world. Nepal suffers from inadequate investment in the energy efficiency improvement and
renewable energy in the industrial sector. Literatures suggest that the key barriers to the
implementation of energy efficiency are lack of awareness and access to finance. The banks
as the financing institutions also have limited knowledge of EE projects and there is a need to
improve awareness. Hence the main objective of this study was to estimate the investment
potential for EE and RE projects as well as energy savings and renewable energy potential in
the industrial sectors. Several international donor agencies/countries have launched and are
launching various programs and projects for the sustainable industrial development in Nepal
with motive of making Nepalese industries energy efficient.
S. No Name of Program/ Project Major Activities
1 Nepal -GTZ Energy Efficiency
Program (NEEP-Project of GTZ)
NEEP-GTZ is working on 3 components:
Integration of EE as part of the national energy
strategy for the efficient use of energy, including
biomass,
Development of EE measures for more efficient
use of biomass in rural households and the
efficient use of electricity in urban households,
and
Making energy intensive industrial enterprises
more energy efficient and economic.

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2 Strengthening of Environmental
Administration and Management at
the Local Level in Nepal (SEAM-
N)
To improve the state of the environment and to
enhance environmentally sustainable and
industrial development and utilization of natural
resources in the project area (Eastern part of
Nepal)
3 Energy Sector Assistance Program
(ESAP)
One of the major programs of AEPC signed
between GON and the Government of Denmark
(Danida) in March 1999 to provide decentralized
renewable energy services to rural as well as
urban communities
4 Biogas Support Program (BSP) One of the major programs of AEPC to promotes
Biogas technology which is first Clean
Development Mechanism (CDM) project in
Nepal
5 Rural Energy Development
Program (REDP)
With financial and technical assistance from
UNDP, REDP is working on installation of
micro hydro, SHS, Biogas plants, ICS
6 Vertical Shaft Brick Kiln
Project/Nepal (VSBK)
Bilateral agreement between SDC and GON to
implement energy efficient VSBK technology
for brick making in Nepal
7 Environment Sector Program
Support (ESPS)
Assistance from DANIDA for the overall
environmental management of the brown sector
in Nepal through concerned ministries to
promote CP, EMS, EE, OHS in the industrial
districts of Nepal
(source: NEEP report)
3.3 ENERGY MANAGEMENT:
Basically, whenever the term efficiency is used we understand it as the ratio of output
to input of any processing system. Therefore in physical terms, energy efficiency means the
effective use of energy, be it electrical, thermal, light, sound, etc.; that enables commercial,
industrial and institutional facilities to minimize operating cost and improve profits to stay
competitive.
“lower energy use leaves experts pleased but puzzled”
Dating back to ancient times, we can observe that use of time clocks for automatic
toggling, bimetallic thermostat for temperature control, etc are some examples of energy

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management. Manually toggling on and off of devices based upon need is a rudimentary
form of energy management. Hence, energy management is the control of energy consuming
devices for the purpose of minimizing energy demand and consumption. The strategy of
adjusting and optimizing energy, using systems and procedures so as to reduce energy
requirements per unit of output while holding constant or reducing total costs of
producing the output from these systems is the basic theme of energy management.
Managing energy is not just technical challenge, but one with one of how to best implement
those technical challenges within economic limits and with a minimum of disruption. Taking
this into account energy management basically deals with following three things:
 Detailed examination of how a facility uses energy.
 What facility pays for that energy.
 A recommended program for changes in operating practices or energy-
consuming equipment that will cost-effectively save dollars on energy
bills.
“The judicious and effective use of energy to maximize profits (minimize costs) and enhance
competitive positions is Energy Management”
(Cape Hart, Turner and Kennedy, Guide to Energy Management Fairmont press inc. 1997)
In todays world almost all the utilities run with the help of energy such as space conditioning,
boiler fuel, direct process heat, feedstock, lighting and mechanical drives. Thus, high
competition in the global market place and increased environmental standards to reduce
environmental pollution, the operational cost, and capital investment decisions for any
organization have become more complex. Hence, energy management has evolved as an
important tool to help organizations meet these critical objectives for their short-term survival
and long-term success. Energy management itself is a vague term to explain as it includes
every type of energy as well as its use and management. So after knowing the fundamental
basic of energy management I would like to focus the reader’s attention in energy
audit/energy efficiency programme of industry especially in motors and drives system.
Energy Audit is the key to a systematic approach for decision-making in the area of energy
management. It is defined as the verification, monitoring and analysis of use of energy
including submission of technical report containing recommendations for improving energy
efficiency with cost benefit analysis and an action plan to reduce energy consumption .It
attempts to balance the total energy inputs with its use, and serves to identify all the energy
streams in a facility. It quantifies energy usage according to its discrete functions. Industrial
energy audit is an effective tool in defining and pursuing comprehensive energy
management programme. Energy audit can better be understood by the acronym IS A i.e.
energy audit means Inspection, Survey and Analysis of energy for energy conservation in the
various facilities to reduce the amount of energy input into the system without negatively
affecting the output.
Need of energy audit:
In any industry, the three top operating expenses are often found to be energy (both electrical
and thermal), labour and materials. If one were to relate to the manageability of the cost or

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potential cost savings in each of the above components, energy would invariably emerge as a
top ranker, and thus energy management function constitutes a strategic area for cost
reduction. Energy Audit will help to understand more about the ways energy and fuel are
used in any industry, and help in identifying the areas where waste can occur and where
scope for improvement exists. Primary objective of Energy Audit is to determine ways to
reduce energy consumption per unit of product output or to lower operating costs and also
provides a “ bench-mark” (Reference point) for managing energy in the organization.
Audit parameters:
Proper energy audit seeks to prioritize the energy uses according to the greatest to least cost
effective opportunity for energy savings. Energy auditing also quantifies the energy in
different parameters:
 Electrical Parameters
 Voltage (V),
 Current (I),
 Power factor,
 Active power (kW),
 Apparent power (demand)
(kVA),
 Reactive power (kVAr),
 Energy consumption
(kWh),
 Frequency (Hz),
 Harmonics, etc.
 Other parameters
 Temperature
 air and gas flow,
 liquid flow,
 revolutions per minute,
 noise and vibration,
 dust concentration,
 TDS, pH,
 moisture content,
 relative humidity,
 flue gas analysis
 combustion efficiency etc.
Energy audit is carried out by a well skilled professional in appropriate order. The basic
steps of energy audit is:
 Phase 1- pre audit phase:
 Plan and organize
 Walk through audit
 Informal interview with energy manager, production/plant manager
 Conduct of brief meeting/ awareness programme with all divisional
heads and persons concerned
 Phase 2- audit phase:
 Primary data gathering, process flow diagram & energy utility
diagram.
 Conduct survey and monitoring
 Conduct of detailed trials/experiments for selected energy guzzlers
 Analysis of energy use.
 Identification and development of energy conservation (ENCON)
opportunities.
 Cost benefit analysis
 Reporting & presentation to top management

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 Phase 3- post audit phase:
 Implementation and follow-up.
Tools most commonly needed for energy audit are tape measure, lightmeter, thermometers,
infrared cameras, multimeter, clamp-on meter, wattmeter/power factor meter, combustion
analyzer, air flow measurement device, safety equipment, miniature data logger, vibration
analyzer gear,etc. with the proper guidance successful accomplishment of energy audit is
achieved and the findings are implemented for preventing energy losses in the facility. Since
this seminar paper is limited to electrical part .i.e. in motors only, followings are the major
electrical audit tools:
3.4 ELECTRIC MOTORS
An electric motor is an electromechanical device that converts electrical energy to
mechanical energy.
Mechanical energy = product of electrical energy * efficiencies
Electrical Measuring Instruments:
These are instruments for measuring major electrical parameters such as kVA, kW, PF, Hertz,
kVAr, Amps and Volts. In addition some of these instruments also measure harmonics.
And below is the figure of some other energy auditing equipments.

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This mechanical energy is used for, for example, rotating a pump impeller, fan or blower,
driving a compressor, lifting materials etc. almost all type of machineries in the industry uses
motor as its driving power. Electric motors are used at home (mixer, drill, fan) and in
industry. Electric motors are sometimes called the “work horses” of industry because it is
estimated that motors use about 70% of the total electrical load in industry.
Types of Electric Motors:
An electric current
in a magnetic field
experience a
force.
If the current-carrying wire is
bent into a loop, then the two
sides of the loop which are at
right angles to the magnetic
field will experience forces in
opposite directions.
The pair of forces
creates a turning
influence or torque
to rotate the coil
Practical motors have several
loops on an armature to
provide a more uniform
torque and magnetic field is
produced by an electromagnet
arrangement called the field
coils

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Among these different types of motors, the most commonly used motors in the industries is
INDUCTION MOTOR. Their popularity is due to their simple design, they are inexpensive
and easy to maintain, and can be directly connected to an AC power source.
Fig: induction motor
Its working principle:
Electricity is supplied to the stator, which generates a magnetic field. This magnetic field
moves at synchronous speed around the rotor, which in turn induces a current in the rotor.
The rotor current produces a second magnetic field, which tries to oppose the stator magnetic
field, and this causes the rotor to rotate. In practice however, the motor never runs at
synchronous speed but at a lower “base speed”.
The difference between these two speeds is the “slip”, which increases with higher loads. Slip
only occurs in all induction motors. To avoid slip, a slip ring can be installed, and these
motors are called “slip ring motors”.
% Slip = ((Ns – Nb) x 100)/Ns
(Where:
Ns = synchronous speed in RPM
Nb = base speed in RPM)

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4. FINDINGS AND ANALYSIS
4.1 NEPALESE ENERGY SCENARIO:
(source: WECS Energy synopsis report 2010)
The above figure is self explanatory to illustrate the energy consumption (by fuel type)
scenario in nepalese industries.The source of energy may be different but the major form of
energy required by manufacturing industries is electrical energy. Nepal is a rich source of
hydroelectricity but the irony is; it is not being successful in fulfilling the industrial electrical
energy need. Electrical energy is the top ranked necessity of any type of industry.
Electricity must be generated when it is needed since electricity cannot be stored. The
generated power is transmitted to the user through a transmission and distribution network,
which consists of transformers, transmission lines and control equipment.
Petroleum
8% Coal
2%
Electricity
2%
Biogas
0.6%
Microhydro
0.15%
Solar
0.05%
Fuel wood
78%
Agr residue
4%
Animal dung
6%
Energy Consumption by Fuel Type
Generator
0.6 KV
Power plant
220 KV
Transmission System
Step down
Distribution System

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Electricity consumption by various sectors.
Electric load forecast for Nepal.
(source NEEP/GIZ)
Above figure shows the electrical energy consumption on the basis of different sectors. We
can clearly observe that industry is the prime user of electricity. The industrial sector share of
energy consumption is about 3.5% of the total energy consumption in Nepal, taking thus the
third place after residential sector and transport sector so far as the share of sectoral
consumption is concerned. More than half of this energy requirement is met by coal followed
by electricity (23%). The main end uses of electricity in this sector are motive power, heating
and lighting. So this seminar paper is basically focused on energy efficiency with electrical

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energy only. And amongst the utilities of electrical energy motors are the main entity to be
considered because almost all the industrial electrical machine is operated by motors and
drive mechanism.
We can see that besides residential use, industry is the major user of electricity in the
country. So electrical energy efficiency seems to be indispensible for the Nepalese industries.
It is a well known fact that saving energy means producing energy, so the main theme of this
report is to create awareness about efficient use of energy and make Nepal known for its
energy efficient industries. Similarly below drawn figure represents the electric load forecast
of Nepal. We can see that the electric load demand is increasing exponentially with the
annual growth rate of 7.56%. using this data we can prepare ourselves for generating more
electricity in coming years to avoid the loadshedding in near future. The nation should invest
more and more in hydropower sector as Nepal is second richest country in terms of water
resources. The nation should also encourage other source of electricity such as solar grid,
biomass, wind energy so as to contribute towards counteracting the forecasted electric load
demand.
4.2 ASSESSMENT OF ELECTRIC MOTORS
The two parameters of importance in a motor are efficiency and power factor.
Efficiency of electric motors: Motors convert electrical energy to mechanical energy to serve
a certain load. In this process, energy is lost as shown in Figure.
losses
MotorPower Input
Load
Power O/P

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Efficiency:
The efficiency of the motor is given by:
= = 1 −
where, pout – output power of the motor
pin – input power of the motor
ploss - losses occurring in motor
motor loading:
=

× 100
Figure. Motor Losses (US DOE)
The efficiency of a motor is determined by intrinsic losses that can be reduced only by
changes in motor design and operating condition. Losses can vary from approximately two
percent to 20 percent. Table shows the types of losses for an induction motor.
Types of losses Percentage of
total loss (100%)
Efficiency improvement
Fixed loss or core loss
= no load power(watts)-(no
load current)^2*stator
resistance
25 Use of thinner gauge, lower loss
core steel reduces eddy current
losses. Longer core adds more
steel to the design, which reduces
losses due to lower operating flux
densities.
Variable loss: stator I^2
loss.
Correctionfactor= =
34 Use of more copper and larger
conductors increases cross
sectional area of stator windings.
This lowers resistance (R) of the
windings and reduces losses due to
current flow (I).
Variable loss: rotor I^2 loss
=slip*(stator input-stotor
I^2R losses-core loss)
21 Use of larger rotor conductor bars
increases size of cross section,
lowering conductor resistance (R)
and losses due to current flow (I).
Friction and rewinding loss 15 Use of low loss fan design reduces
losses due to air movement.
Stray load loss 5 Use of optimized design and strict
quality control procedures
minimizes stray load losses.

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The efficiency of a motor can be defined as “the ratio of a motor’s useful power output to its
total power input.”
Factors that influence motor efficiency include:
 Age- New motors are more efficient
 Capacity- As with most equipment, motor efficiency increases with the rated capacity
 Speed- Higher speed motors are usually more efficient
 Type- For example, squirrel cage motors are normally more efficient than slip-ring
motors
 Temperature- Totally-enclosed fan-cooled (TEFC) motors are more efficient than
screenprotected drip-proof (SPDP) motors
 Rewinding of motors can result in reduced efficiency
while in power measurements are fairly simple, measurement of output or losses need a
laborious exercise with extensive testing facilities. Because the efficiency of a motor is
difficult to assess under normal operating conditions, the motor load can be measured as
an indicator of the motor’s efficiency. As loading increases, the power factor and the motor
efficiency increase to an optimum value at around full load.
The following equation is used to determine the load:
Load = (Pi x η)/(HP x 0.7457)
Where,
η = Motor operating efficiency in %
HP = Nameplate rated horse power
Load = Output power as a % of rated power & Pi = Three phase power in kW
Estimation of efficiency in the field can be summarized as follows:
a) Measure stator resistance and correct to operating temperature. From rated current
value, I2
R losses are calculated.
b) From rated speed and output, rotor I2
R losses are calculated.
c) From no load test, core and F & W losses are determined for stray loss.
Illustrative example:
Motor specifications: rated power=34kW/45HP; voltage=415V; current=57A; speed 1475
rpm; connection=delta.
No load test data: voltage=415V; current= 16.1A; frequency= 50Hz; stator phase resistance at
30oC= 0.264 Ohms; No load power, Pnl=1063.74 Watts.
 Calculation of iron plus friction and windage losses:
Let iron plus friction and windage loss= Pi+FW
No load power, Pnl= 1063.74 W
Stator copper loss, Pst-30oC= 3*(16.1/sqrt3)^2*0.264=68.43 W

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Therefore,
Pi+FW= Pnl-Pst=1063.74-68.43=995.3 W
 Calculation of stator resistance at 120oC:
R120oC =0.264*((120+235)/(30+235)) = 0.354 Ohms per phase
 Calculation Stator copper losses at operating temperature of resistance at 120oC:
= 3*(57/sqrt3)^2*0.354
= 1150.1 W
 Calculation of full load slip(s) and rotor input assuming rotor losses are slip times
rotor input.
Full load slip(S)=(1500-1475)/1500=0.0167
Roto input, Pr= Poutput/(1-S) = 34000/(1-0.0167) = 34577.4 Watts
 Calculation of motor input assuming that stray losses are 0.5% of the motor rated
power:
Motor full load input power, Pinput= Pr + Pst.cu120oC +(Pi+FW)+Pstray
= 34577.4+1150.1+995.3+(0.005^2*34000)
=36892.8 Watts (where stray losses=0.5% of rated output(assumed))
 Calculation of motor full load efficiency and full load power factor:
Efficiency=(Poutput*100)/Pinput =34000*100/36892.8 = 92.2%
Full load power factor = Pinput/(sqrt3*V*In) =36892.8/(sqrt3*415*57) = 0.90
Comments:
 The measurement of stray load losses is very difficult and not practical
even on test beds.
 The actual value of stray loss of motors upto 200HP is likely to be 1%
to 3% compared to 0.5% assumed by standards.
 The value of full load slip taken from the nameplate data is not
accurate. Actual measurement under full load conditions will give
better results.
 The friction and windage losses really are part of the shaft output;
however, in the above calculation, it is not added to the rated shaft
output, before calculating the rotor input power. The error however is
minor.
 When a motor is rewound, there is a fair chance that the resistance per
phase would increase due to winding material quality and the losses
would be higher. It would be interesting to assess the effect of a
nominal 10% increase in resistance per phase.

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Besides these particulars, the management side boasts on calculating payback period
and annual energy savings as well.
Simple payback period=(price premium-utility rebate)/annual dollar saving
KWsaved= rating of the motor* ((100/Estd)-(100/EHE))
Where:
Estd= standard motor efficiency under full load condition,
EHE= energy efficient motor efficiency under full load conditions
The kilowatt savings are the demand savings.
Motor field measurement format

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Power factor
Power factor is relevant to AC power transmission. The power factor is the ratio between
active power (kW) and total power (kVA), or the cosine of the angle between active and total
power. A high reactive power, will increase this angle and as a result the power factor will be
lower.
Fig: power factor of electric circuit.
The power factor is always less than or equal to one. Theoretically, if all loads of the
power supplied by electricity companies have a power factor of one, the maximum power
transferred equals the distribution system capacity. However, as the loads are inductive and if
power factors range from 0.2 to 0.3, the electrical distribution network’s capacity is stressed.
A poor power factor is caused by loads being reactive (capacitative, or more commonly,
inductive) rather than resistive. Basically, what happens is that the inductive components
soak up some of the "power" which comes down the supply line temporarily to create a
magnetic field. As this magnetic field collapses, they "push" the power back into the power
grid. This causes the current in the supply line to be out-of-phase with the voltage.Hence, the
reactive power (kVAR) should be as low as possible for the same kW output in order to
minimize the total power (kVA) demand.
Capacitors to Improve the Power Factor
The power factor can be improved
by installing power factor correction
capacitors (see Figures) to the plant’s
power distribution system. They act as
reactive power generators and therefore
reduce the amount of reactive power, and
thus total power generated by the utilities.
Active Power(KW)
Reactive Power
(KVAR)
Total or Real
Power (KVA)

=

=kW/kVA
= cosine(phi)

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Fig: capacitor as kVAR current.
Fig: film type capacitor banks
An illustrative example showing the power factor improvement by capacitor installation is
shown below:
A chemical plant installed a 1500 kVA transformer. The initial demand of the plant was 1160
kVA with power factor of 0.70. The percentage loading of the transformer was about 78
percent (1160/1500 = 77.3 percent). To improve the power factor and to avoid penalties
charged by the electricity supplier, the plant added about 410 kVAr in motor load. This
improved the power factor to 0.89, and reduced the required kVA to 913, which is the vector
sum of kW and kVAr. The 1500 kVA transformer was now loaded only to 60 percent of its
capacity. This will allow the plant to add more load to the transformer in the future. (NPC
Field Study)
KW= 812
KW = 812
KVA = 1160 KVAR = 828 KVA = 913
PF = 812/913=0.89
PF = 812/1160
=0.70
Advantages of Power Factor Improvement by Capacitor Addition
The advantages of an improved power factor through the installation of a capacitor are:
Cosphi
=.70
Cos
phi=
.89
KVAR=
828-
410=4
18

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For the company:
 A one-off investment in purchasing and installing the capacitor is needed but there are no
ongoing costs
 Reduced electricity costs for the company because (a) the reactive power (kVAR) is no
longer supplied by the utility company and therefore the total demand (kVA) is reduced
and (b) penalty charges imposed when operating with a low power factor are eliminated.
 Reduced distribution losses (kWh) within the plant network
 Voltage level at the load end is increased resulting in improved performance of motors
For the utility supplying electricity:
 Reactive component of the network and the total current in the system from the source
end are reduced
 I2R power losses are reduced in the system because of reduction in current
 Available capacity of the electricity distribution network is increased, reducing the need
to install additional capacity
4.3 ENERGY EFFICIENCY OPPORTUNITIES
This section includes factors affecting electric motor performance, losses assessment and
improvements in efficiency.
Replace standard motors with energy efficient motors
High efficiency motors are designed specifically to increase operating efficiency compared to
standard motors. Design improvements focus on reducing intrinsic motor losses (explained
above) and include the use of lower-loss silicon steel, a longer core (to increase active
material), thicker wires (to reduce resistance), thinner laminations, smaller air gap between
stator and rotor, copper instead of aluminum bars in the rotor, superior bearings and a smaller
fan, etc. Energy efficient motors cover a wide range of ratings and the full load. Efficiencies
are 3% to 7% higher compared with standard motors as shown in Figure. And the table
drawn above describes the improvement opportunities that are often used in the design of
energy efficient motors.

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Figure 12. Comparison between high efficiency and standard motor
As a result of the modifications to improve performance, the costs of energy efficient motors
are higher than those of standard motors. The higher cost will often be paid back rapidly
through reduced operating costs, particularly in new applications or end-of-life motor
replacements. But replacing existing motors that have not reached the end of their useful life
with energy efficient motors may not always be financially feasible, and therefore it is
recommended to only replace these with energy efficiency motors when they fail.
Reduce under-loading (and avoid over-sized motors)
As explained above, under-loading increases motor losses and reduces motor efficiency and
the power factor. Under-loading is probably the most common cause of inefficiencies for
several reasons:
 Equipment manufacturers tend to use a large safety factor when selecting the motor.
 Equipment is often under-utilized. For example, machine tool equipment
manufacturers provide for a motor rated for the full capacity load of the equipment. In
practice, the user may rarely need this full capacity, resulting in under-loaded
operation most of the time.
 Large motors are selected to enable the output to be maintained at the desired level
even when input voltages are abnormally low.
 Large motor are selected for applications requiring a high starting torque but where a
smaller motor that is designed for high torque would have been more suitable.
The motor size should be selected based on a careful evaluation of the load. But when
replacing an oversized motor with a smaller motor, it is also important to consider the
potential efficiency gain. Larger motors have inherently higher rated efficiencies than smaller
motors. Therefore, the replacement of motors operating at 60 – 70% of capacity or higher is
generally not recommended. On the other hand there are no rigid rules governing motor
selection and the savings potential needs to be evaluated on a case-by-case basis. For
example, if a smaller motor is an energy efficient motor and the existing motor not, then the
efficiency could improve. For motors that consistently operate at loads below 40% of the
rated capacity, an inexpensive and effective measure could be to operate in star mode. A
change from the standard delta operation to a star operation involves re-configuring the
wiring of the three phases of power input at the terminal box. Operating in the star mode
leads to a voltage reduction by factor ‘√3’. The motor is
electrically downsized by star mode operation, but performance characteristics as a function
of load remain unchanged. Thus, motors in star mode have a higher efficiency and power
factor when in full-load operation than partial load operation in the delta mode.
However, motor operation in the star mode is possible only for applications where the torque
to- speed requirement is lower at reduced load. In addition, conversion to star mode should be
avoided if the motor is connected to a production facility with an output that is related to the
motor speed (as the motor speed reduces in star mode). For applications with high initial
torque and low running torque requirements, Delta-Star starters are also available, which help
to overcome high initial torque.
Sizing to variable load
Industrial motors frequently operate under varying load conditions due to process
requirements. A common practice in this situation is to select a motor based on the highest
anticipated load. But this makes the motor more expensive as the motor would operate at full

22
capacity for short periods only, and it carries the risk of motor under-loading. An alternative
is to select the motor rating based on the load duration curve of a particular application.
This means that the selected motor rating is slightly lower than the highest anticipated load
and would occasionally overload for a short period of time. This is possible as manufacturers
design motors with a service factor (usually 15% above the rated load) to ensure that running
motors above the rated load once in a while will not cause significant damage. The biggest
risk is overheating of the motor, which adversely affects the motor life and efficiency and
increases operating costs. A criteria in selecting the motor rating is therefore that the
weighted average temperature rise over the actual operating cycle should not be greater than
the temperature rise under continuous full-load operation (100%). Overheating can occur
with:
 Extreme load changes, such as frequent starts / stops, or high initial loads
 Frequent and/or long periods of overloading
 Limited ability for the motor to cool down, for example at high altitudes, in hot
environments or when motors are enclosed or dirty Where loads vary substantially with
time, speed control methods can be applied in addition to proper motor sizing (see section
speed control of induction motor).
Improving power quality
Motor performance is affected considerably by the quality of input power, which is
determined by the actual volts and frequency compared to rated values. Fluctuation in
voltage and frequency much larger than the accepted values has detrimental impacts on motor
performance. Voltage unbalance can be even more detrimental to motor performance and
occurs when the voltages in the three phases of a three-phase motor are not equal. This is
usually caused by the supply different voltages to each of the three phases. It can also result
from the use of different cable sizes in the distribution system. An example of the effect of
voltage unbalance on motor performance is shown in table below. The voltage of each phase
in a three-phase system should be of equal magnitude, symmetrical, and separated by 120°.
Phase balance should be within 1% to avoid de-rating of the motor and voiding of
manufacturers’ warranties. Several factors can affect voltage balance: single-phase loads on
any one phase, different cable sizing, or faulty circuits. An unbalanced system increases
distribution system losses and reduces motor efficiency.
Table. Effect of Voltage Unbalance in Induction Motors (BEE India, 2004)
Example 1 Example 2 Example 3
Percentage unbalance
in voltage
.3 2.3 5.4
Unbalance to
current(%)
.4 17.7 40
Increase in
temperature(0c)
0 30 40
* Percent unbalance in voltage = (maximum deviation from mean voltage / mean voltage) x
100
Voltage unbalance can be minimized by:
 Balancing any single phase loads equally among all the three phases
 Segregating any single phase loads which disturb the load balance and feed them from a
separate line / transformer

23
Rewinding
It is common practice in industry to rewind burnt-out motors. The number of rewound
motors in some industries exceeds 50% of the total number of motors. Careful rewinding can
sometimes maintain motor efficiency at previous levels, but in most cases results in
efficiency losses. Rewinding can affect a number of factors that contribute to deteriorated
motor efficiency: winding and slot design, winding material, insulation performance, and
operating temperature. For example, when heat is applied to strip old windings the insulation
between laminations can be damaged, thereby increasing eddy current losses. A change in the
air gap may affect power factor and output torque. However, if proper measures are taken, the
motor efficiency can be maintained after rewinding, and in some cases efficiency can even be
improved by changing the winding design. Using wires of greater cross section, slot size
permitting, would reduce stator losses and thereby increasing efficiency. However, it is
recommended to maintain the original design of the motor during the rewind, unless there are
specific load-related reasons for redesign. The impact of rewinding on motor efficiency and
power factor can be easily assessed if the no-load losses of a motor are known before and
after rewinding. Information of no-load losses and no-load speed can be found in
documentation of motors obtained at the time of purchase. An indicator of the success of
rewinding is the comparison of no load current and stator resistance per phase of a rewound
motor with the original no-load current and stator resistance at the same voltage.
When rewinding motors it is important to consider the following:
 Use a firm that ISO 9000 certified or is member of an Electrical Apparatus Service
Association.
 Motors less than 40 HP in size and more than 15 years old (especially previously
rewound motors) often have efficiencies significantly lower than currently available
energy-efficient models. It is usually best to replace them. It is almost always best to
replace non-specialty motors under 15 HP.
 If the rewind cost exceeds 50% to 65% of a new energy-efficient motor price, buy the
new motor. Increased reliability and efficiency should quickly recover the price premium.
Power factor correction by installing capacitors
As noted earlier, induction motors are characterized by power factors less than one, leading to
lower overall efficiency (and higher overall operating cost) associated with a plant’s electrical
system. Capacitors connected in parallel (shunted) with the motor are often used to
improve the power factor. The capacitor will not improve the power factor of the motor itself
but of the starter terminals where power is generated or distributed. The benefits of power
factor correction include:
 reduced kVA demand (and hence reduced utility demand charges),
 reduced I2R losses in cables upstream of the capacitor (and hence
reduced energy charges),
 reduced voltage drop in the cables (leading to improved voltage
regulation),
 increase in the overall efficiency of the plant electrical system.
The size of capacitor depends upon the no-load reactive kVA (kVAR) drawn by the motor.
This size should not exceed 90% of the no-load kVAR of the motor, because higher
capacitors could result in too high voltages and motor burn-outs. The kVAR of the motor can
only be determined by no-load testing of the motor. An alternative is to use typical power
factors of standard motors to determine the capacitor size.

24
Improving maintenance
Most motor cores are manufactured from silicon steel or de-carbonized cold-rolled steel, the
electrical properties of which do not change measurably with age. However, poor
maintenance can cause deterioration in motor efficiency over time and lead to unreliable
operation. For example, improper lubrication can cause increased friction in both the motor
and associated drive transmission equipment. Resistance losses in the motor, which rise with
temperature, would increase. Ambient conditions can also have a detrimental effect on motor
performance. For example, extreme temperatures, high dust loading, corrosive atmosphere,
and humidity can impair insulation properties; mechanical stresses due to load cycling can
lead to misalignment. Appropriate maintenance is needed to maintain motor performance. A
checklist of good maintenance practices would include:
 Inspect motors regularly for wear in bearings and housings (to reduce frictional losses)
and for dirt/dust in motor ventilating ducts (to ensure proper heat dissipation)
 Check load conditions to ensure that the motor is not over or under loaded. A change in
motor load from the last test indicates a change in the driven load, the cause of which
should be understood
 Lubricate appropriately. Manufacturers generally give recommendations for how and
when to lubricate their motors. Inadequate lubrication can cause problems, as noted
above. Over-lubrication can also create problems, e.g. excess oil or grease from the motor
bearings can enter the motor and saturate the motor insulation, causing premature failure
or creating a fire risk
 Check periodically for proper alignment of the motor and the driven equipment. Improper
alignment can cause shafts and bearings to wear quickly, resulting in damage to both
themotor and the driven equipment
 Ensure that supply wiring and terminal box are properly sized and installed. Inspect
regularly the connections at the motor and starter to be sure that they are clean and tight
 Provide adequate ventilation and keep motor cooling ducts clean to help dissipate heat to
reduce excessive losses. The life of the insulation in the motor would also be longer: for
every 10o
C increase in motor operating temperature over the recommended peak, the time
before rewinding would be needed is estimated to be halved
Speed control of induction motor
Traditionally, DC motors were used when variable speed capability was desired. But because
of the various limitations of DC motors , AC motors are increasingly the focus for variable
speed applications. Both AC synchronous and induction motors are suitable for variable
speed control. Because an induction motor is an asynchronous motor, changing the supply
frequency can vary the speed. The control strategy for a particular motor will depend on a
number of factors including investment cost, load reliability and any special control
requirements. This requires a detailed review of the load characteristics, historical data on
process flows, features required of the speed control system, the electricity tariffs and the
investment costs. The characteristics of the load (explained above) are particularly important
in deciding whether speed control is an option. The largest potential for electricity savings
with variable speed drives is generally in variable torque applications, for example
centrifugal pumps and fans, where the power requirement changes as the cube of speed.
Constant torque loads are also suitable for VSD application.

25
Multi-speed motors
Motors can be wound such that two speeds, in the ratio of 2:1, can be obtained. Motors can
also be wound with two separate windings, each giving two operating speeds and thus a total
of four speeds. Multi-speed motors can be designed for applications involving constant
torque, variable torque, or for constant output power. Multi-speed motors are suitable for
applications that require limited speed control (two or four fixed speeds instead of
continuously variable speed). These motors tend to be very economical as their efficiency is
lower compared to single-speed motors.
Variable speed drives (VSDs)
Variable speed drives (VSDs) are also called inverters and can change the speed of a
motor. They are available in a range several kW to 750 kW. They are designed to operate
standard induction motors and can therefore be easily installed in an existing system.
Inverters are often sold separately because the motor may already be in place, but can also be
purchased together with a motor. When loads vary, VSDs or two-speed motors can often
reduce electrical energy consumption in centrifugal pumping and fan applications by 50% or
more. The basic drive consists of the inverter itself which converts the 50 Hz incoming power
to a variable frequency and variable voltage. The variable frequency will control the motor
speed. There are three major types of inverters designs available today. These are known as
Current Source Inverters (CSI), Variable Voltage Inverters (VVI), and Pulse Width
Modulated Inverters (PWM).
Direct current drives (DCDs)
The DC drive technology is the oldest form of electrical speed control. The drive system
consists of a DC motor and a controller. The motor is constructed with an armature and field
windings. The field windings require a DC excitation for motor operation, usually with a
constant level voltage from the controller. The armature connections are made through a
brush and commutator assembly. The speed of the motor is directly proportional to the
applied voltage. The controller is a phase-controlled bridge rectifier with logic circuits to
control the DC voltage delivered to the motor armature. Speed control is achieved by
regulating the armature voltage to the motor. Often a tacho-generator is included to achieve
good speed regulation. The tacho-generator would be mounted onto the motor to produce a
speed feedback signal that is used inside the controller.
Wound rotor AC motor drives (slip ring induction motors)
Wound rotor motor drives use a specially constructed motor to accomplish speed control. The
motor rotor is constructed with windings that are lifted out of the motor through slip rings on
the motor shaft. These windings are connected to a controller, which places variable resistors
in series with the windings. The torque performance of the motor can be controlled using
these variable resistors. Wound rotor motors are most common in the range of 300 HP and
above.

26
5. CONCLUSION & RECOMMENDATIONS.
Hence, Nepal relies heavily on traditional energy resources, as no significant deposits of
fossil fuel are available. The energy scenario of Nepalese industries seems quite unmanaged
and inefficient as well. Only some of the reputed companies are well aware of implementing
energy efficiency. Through this report I have tried to expose the current scenario of the
Nepalese industry in terms of energy. A detailed analysis of the energy efficiency of the
industrial motors has been presented in this paper. One part of the fixed losses may be
reduced by using advances materials with smaller area of hysteresis loop and another part by
using better stacking of the core and high resistivity material. Friction and windage losses
may be reduced using better aerodynamic design of rotor and bearing with low friction. The
optimum design gives a motor having uniformly high efficiency over a wide range of load
and supply voltage.And as motors are the indispensible need of every type of industries, I
have also explained the methodologies of energy efficiency in electrical motors used in the
industry. With the main moto of “saving 1 unit = producing 2 units” I have so far tried to
explain the efficiency opportunities, possible losses and proper assessment of electrical
motors. If the proper care of such electrical appliances are taken then we Nepalese can really
save lots of energy losses. Therefore I strongly recommend the Nepalese government to
formulate the suitable policies to make the industrialist operate their industry efficiently and
also provide training on industrial energy efficiency at national level including the
representative of all the major industries of the country. Investing on projects to carry out
energy efficiency in motors certainly benefits the company by reducing its overhead cost.

27
6. BIBLIOGRAPHY & REFERENCES
 BEE Energy Guide,2004
 Nepalese Energy Module, NEEP
 Electrical Energy scenario of Nepal Cylinders (P) Ltd., Amlekhgunj.
 Field visit and site study of Pashupati Iron and Steels Industry, Sonapur.
 Energy Guide Industry Asia, UNEP.
 Old Reports
 NEMA, (1997): Scope of elctric motors subject to efficiency standards:Energy Policy
Act-1992, pp. 1-8.
 Annual progress report, Alternative Energy Promotion Centre.
 www.wikipedia.com

28
Table of Contents
Certificate
Acknowledgement
1. BACKGROUND/INTRODUCTION................................................................................................ 1
2. OBJECTIVE OF THE TOPIC..................................................................................................... 2
3. LITERATURE REVIEW ................................................................................................................. 3
3.1 Types of nepalese industries ................................................................................................ 3
3.2 Main manufacturing industry distribution in the country ................................................ 4
3.3 Energy management............................................................................................................. 5
3.4 Electric motors...................................................................................................................... 8
4. FINDINGS AND ANALYSIS........................................................................................................ 11
4.1 Nepalese energy scenario: .................................................................................................. 11
4.2 Assessment of electric motors ........................................................................................... 13
4.3 Energy efficiency opportunities......................................................................................... 20
5. CONCLUSION & RECOMMENDATIONS. ................................................................................... 26
6. BIBLIOGRAPHY & REFERENCES................................................................................................ 27

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