Energy Audit Practitioner Course Energy Management System (EnMS)

1. Energy Audit Practitioner Course
Energy Management System
(EnMS)
Engr. Abdul Qayoom
Senior Consultant / Trainer
Certified Trainer on Energy Management System – (Germany)
Certified Auditor GHK Premer- (Germany)
Certification of MFCA (ISO 14051:2013)- Taiwan Republic of China
Certification of Six Sigma Green Belt (Vitaman)
Certified Productivity Specialist -(Pakistan)
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2. Basic IntroductionGREEN PRODUCTIVITY
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1.4 Energy Efficiency in Electrical Motor
ModuleI

3. • Motors convert electrical energy into mechanical energy by the
interaction between the magnetic fields set up in the stator and rotor
windings.
• Industrial electric motors can be broadly classified as induction motors,
direct current motors or synchronous motors.
• All motor types have the same four operating components: stator
(stationary windings), rotor (rotating windings), bearings, and frame
(enclosure
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What Is a Motor1.4EnergyEfficiencyofElectricMotor

4. A typical value for an 11 kW standard motor is around 90 per cent and,
for 100 kW, up to 94 per cent. Due to the laws of growth, the efficiency
levels motors are higher than for smaller ones.
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CENTER Motor Efficiency1.4EnergyEfficiencyofElectricMotor

5. It can also be shown that the speed of an AC motor can be varied
infinitely by changing the frequency.
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CENTER Motor Speed1.4EnergyEfficiencyofElectricMotor

6. kVA
kW
CosFactorPower  
As the load on the motor is reduced, the magnitude of the active current
reduces. However, there is not a corresponding reduction in the
magnetizing current, with the result that the motor power factor reduces,
or gets worse, with a reduction in applied load.
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Load Vs. Power Factor1.4EnergyEfficiencyofElectricMotor

7. GREEN PRODUCTIVITY
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1.4EnergyEfficiencyofElectricMotor Reference Case study for understanding

8. GREEN PRODUCTIVITY
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1.4EnergyEfficiencyofElectricMotor Reference Case study for understanding

9. GREEN PRODUCTIVITY
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1.4EnergyEfficiencyofElectricMotor Reference Case study for understanding

10. Range
EnergyLossat
FullLoad(%)
1-10 HP 14.0 - 35
10-50 HP 9.0 - 15
50-200 HP 6.0 - 12
200-1500 HP 4.0 - 07
1500-HP&ABOVE 2.3 - 04
Higher the Rating Higher is the Efficiency
on Account of Reduce Losses
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Range Of Losses In Induction Motors1.4EnergyEfficiencyofElectricMotor
Result = Getting Extra load
Check on Un-loading condition

11. GREEN PRODUCTIVITY
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Life Cycle Cost of a Electric Motor
• Purchase price represents 1.1% of motor life cost
• Installation & maintenance cost 0.2%
• Electricity costs accounts for nearly 98.7%
• Rs 10,000 motor consumes Rs 2,00,000 annual energy and 5%
efficiency advantage saves Rs.10000
1.4EnergyEfficiencyofElectricMotor

12. • 100kw motor giving 1 % more efficiency saves 1kwh per hour that is 5 Rs
• It saves per annum 8000x5=40000 Rs
• If the motor costs Rs 60000 more , it gives payback of 18 months
• And if you decide to replace the 15 year old motor, the efficiency
difference can be 3 %
• The annual saving could be 1.2L and if the motor costs 2.4L, the payback
is just 24 months for the replacement with zero salvage value.
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Electric Motor Payback Calculations1.4EnergyEfficiencyofElectricMotor

13. How to Minimizing Motor Energy Losses in
Operation
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1.4EnergyEfficiencyofElectricMotor

14. Although motors are designed to
operate within 10% of nameplate
voltage, large variations significantly
reduce efficiency, power factor, and
service life
When operating at less than 95% of
design voltage, motors typically lose 2
to 4 points of efficiency, and service
temperatures increase up to 20°F,
greatly reducing insulation life.
Running a motor above its design
voltage also reduces power factor and
efficiency.
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Maintain Voltage Levels1.4EnergyEfficiencyofElectricMotor

15. Voltage unbalance is defined as 100 times the maximum deviation of the
line voltage from the average voltage on a three-phase system divided by
the average voltage. If line voltages measured are 431, 438 and 427 the
average is 432. The voltage unbalance is given by
= 1.1 %
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. 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.
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Minimize Phase Unbalance1.4EnergyEfficiencyofElectricMotor

16. GREEN PRODUCTIVITY
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Reference Case study for understanding1.4EnergyEfficiencyofElectricMotor

17. GREEN PRODUCTIVITY
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1.4EnergyEfficiencyofElectricMotor Reference Case study for understanding

18. GREEN PRODUCTIVITY
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1.4EnergyEfficiencyofElectricMotor Reference Case study for understanding

19. Operating a high capacity motor for lower loads
results in reduced efficiency, power factor and also
increases the energy consumption.
To meet 7.5 kW load if the motor selected is 7.5 /11 /15 kW then the
variations in energy consumption is as shown in Table below: -
Parameter Case 1 Case 2 Case 3
Motor Load 7.5 kw at F.L. 10 kw at 3/4 load 15 kw at ½ load
Required load 7.5 7.5 7.5
Motor EFF (%) 88 84 79
Motor input kw 8.5 9.0 9.5
Unit consumed kwh 42500 45000 47500
% increase -- 5.8 11.76
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Effect Of Over Sizing
Why are motors often oversized?
Original design requires 7kW
Engineer adds in 10% for contingency - 7.7kW
Selects next standard size motor - 11kW
Over rating = 57%
1.4EnergyEfficiencyofElectricMotor

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• Rewinding: sometimes 50% of motors Can reduce motor
efficiency
• Maintain efficiency after rewinding by
• Using qualified/certified firm
• Maintain original motor design
• Replace 40HP, which is >15 year old motors instead of
rewinding
• Buy new motor if costs are less than 50-65% of rewinding
costs
Rewinding of Electric motors1.4EnergyEfficiencyofElectricMotor

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Rewinding of Electric motors1.4EnergyEfficiencyofElectricMotor

22. GREEN PRODUCTIVITY
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Rewinding of Electric motors1.4EnergyEfficiencyofElectricMotor

23. • Rewinding can reduce motor efficiency and reliability if not rewound by
a qualified agency.
• Rewind-versus-replace decision depends on such variables as the rewind
cost, expected rewind loss, energy-efficient motor purchase price, motor
size and original efficiency, load factor, annual operating hours,
electricity price, etc.
• During a motor failure or in the stripping of the winding from the stator
core prior to rewinding, high temperatures can occur. This can affect the
electrical characteristics of the stator core steel and result in increased
iron losses and lower motor efficiency.
• The area of possible loss reduction available during the rewinding is the
ohmic (l2 r) losses in the stator. This is done by rewinding the motor with
a larger diameter wire so that the effective conductor area is increased,
resulting in a lower winding resistance. The effect is to lower the stator
l2 r loss
• Rewinding for lower stator resistance is possible only if additional slot
space is available by the original stator slot not being full of copper or
by utilizing new, thinner insulating material replacing old materials
thereby making more space.
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Minimize Rewind Losses1.4EnergyEfficiencyofElectricMotor

24. Transmission equipment including shafts, belts, chains, and gears should be
properly installed and maintained. When possible, use flat belts in place of
V-belts. Helical gears are more efficient than worm gears; use worm gears
only with motors under 10 hp. As far as possible it is better to have a direct
drive thus avoiding losses in transmission system.
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Optimize Transmission Efficiency1.4EnergyEfficiencyofElectricMotor

25. • Soft starters use thrusters to gradually increase the voltage applied to
the motor, starting slowly and limiting start up currents.
• Since voltage is reduced, current also comes down and there is
reduction in the iron and copper losses.
• Power factor gets improved as the reactive current is reduced due to
lower flux strength requirements, which in turn results in a higher
power factor.
• The starting current with a soft starter is only 1.5 to 2 times the full
load current as against 5 – 7 times in the case of other conventional
starters thereby limiting MD.
• The soft starter application also protect the drive and driven
equipments and will be more beneficial for large number of start/stop
operation.
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Soft Starters For Induction Motors1.4EnergyEfficiencyofElectricMotor

26. GREEN PRODUCTIVITY
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Comparison of Starters1.4EnergyEfficiencyofElectricMotor

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Motors loose energy when serving a load
• Fixed loss
• Rotor loss
• Stator loss
• Friction and rewinding
• Stray load loss
Efficiency of Electric Motors
Assessment of Electric Motors1.4EnergyEfficiencyofElectricMotor

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Factors that influence efficiency
• Age
• Capacity
• Speed
• Type
• Temperature
• Rewinding
• Load
Efficiency of Electric Motors
Assessment of Electric Motors1.4EnergyEfficiencyofElectricMotor

29. • First measure input power Pi with a hand held or in-line power meter
Pi = Three-phase power in kW
• Note the name plate rated kW and Efficiency
• The figures of kW mentioned in the name plate is for output
conditions
• So corresponding input power at full-rated load
hfl =Efficiency at full-rated load
Pir = Input power at full-rated power in kW
The percentage loading can now be calculated as follows
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Input Power Measurements
Assessment of Electric Motor Loading1.4EnergyEfficiencyofElectricMotor

30. GREEN PRODUCTIVITY
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Assessment of Electric Motor Loading
Three methods for individual motors
• Input power measurement
• Ratio input power and rate power at 100% loading
• Line current measurement
• Compare measured amperage with rated amperage
• Slip method
• Compare slip at operation with slip at full load
Electric Motor Loading
1.4EnergyEfficiencyofElectricMotor

31. • The nameplate details of a motor are given as Power = 15 kW,
rated Efficiency h = 0.9
• Using a power meter the actual three phase power drawn is
found to be 8 kW. Find out the loading of the motor.
• Input power at full-rated power in kW, Pir = 15 /0.9
= 16.7 kW
• Percentage loading = 8/16.7
= 48 %
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EXAMPLE1.4EnergyEfficiencyofElectricMotor

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Result
1. Significantly oversized and
under loaded
2. Moderately oversized and
under loaded
3. Properly sized but
standard efficiency
Action
→ Replace with more efficient, properly
sized models
→ Replace with more efficient, properly
sized models when they fail
→ Replace most of these with energy-
efficient models when they fail
Assessment of Electric Motor Loading
Electric Motor Loading
1.4EnergyEfficiencyofElectricMotor

33. The findings may include:
• Identify the motors with <50 %, 50 -75 % , 75-100 % loading, over 100
% loading.
• Identify motors with low voltage / power factor / voltage imbalance
for needed improvement measures.
• Identify motors with machine side losses / inefficiencies like idle
operations, throttling / damper operations for avenues like automatic
controls / interlocks, variable speed drives, etc.
• The margins in motor efficiency may be less than 5% of consumption
often, but the load survey would help to bring out savings in driven
machines / systems, which can give 30 – 40 % energy savings.
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Energy Saving Recommendations in Motors1.4EnergyEfficiencyofElectricMotor

34. GREEN PRODUCTIVITY
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Energy Efficiency Opportunities in Motor
• Use energy efficient motors
• Reduce under-loading (and avoid over-sized motors)
• Size to variable load
• Improve power quality
• Rewinding
• Power factor correction by capacitors
• Improve maintenance
• Speed control of induction motor
1.4EnergyEfficiencyofElectricMotor

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Energy Efficiency Opportunities in Motor
Power Loss Area Efficiency Improvement
1. Fixed loss (iron) 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.
2. Stator I2R Use of more copper & larger conductors increases cross
sectional area of stator windings. This lower resistance (R) of
the windings & reduces losses due to current flow (I)
3 Rotor I2R Use of larger rotor conductor bars increases size of cross
section, lowering conductor resistance (R) & losses due to
current flow (I)
4 Friction & Winding Use of low loss fan design reduces losses due to air movement
5. Stray Load Loss Use of optimized design & strict quality control procedures
minimizes stray load losses
Use Energy Efficient Motors
(BEE India, 2004)
1.4EnergyEfficiencyofElectricMotor

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Energy Efficiency Opportunities in Motor
• Reasons for under-loading
• Large safety factor when selecting motor
• Under-utilization of equipment
• Maintain outputs at desired level even at low input voltages
• High starting torque is required
• Consequences of under-loading
• Increased motor losses
• Reduced motor efficiency
• Reduced power factor
Reduce Under-loading
1.4EnergyEfficiencyofElectricMotor

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Energy Efficiency Opportunities in Motor1.4EnergyEfficiencyofElectricMotor
• Replace with smaller motor
• If motor operates at less than <50%
• Not if motor operates at 60-70%
• Operate in star mode
• If motors consistently operate at <40%
• Inexpensive and effective
• Motor electrically downsized by wire reconfiguration
• Motor speed and voltage reduction but unchanged performance
Reduce Under-loading

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Energy Efficiency Opportunities in Motor
Motor performance affected by
• Poor power quality: too high fluctuations in voltage and
frequency
• Voltage unbalance: unequal voltages to three phases of motor
Improve Power Quality
Example 1 Example 2 Example 3
Voltage unbalance (%) 0.30 2.30 5.40
Unbalance in current (%) 0.4 17.7 40.0
Temperature increase (oC) 0 30 40
1.4EnergyEfficiencyofElectricMotor

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Energy Efficiency Opportunities in Motor1.4EnergyEfficiencyofElectricMotor
• Keep voltage unbalance within 1%
• Balance single phase loads equally among three phases
• Segregate single phase loads and feed them into separate
line/transformer
Improve Power Quality

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Energy Efficiency Opportunities in Motor1.4EnergyEfficiencyofElectricMotor
• Use capacitors for induction motors
• Benefits of improved PF
• Reduced kVA
• Reduced losses
• Improved voltage regulation
• Increased efficiency of plant electrical system
• Capacitor size not >90% of no-load kVAR of motor
Improve Power Factor (PF)

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Energy Efficiency Opportunities in Motor1.4EnergyEfficiencyofElectricMotor
• Checklist to maintain motor efficiency
• Inspect motors regularly for wear, dirt/dust
• Checking motor loads for over/under loading
• Lubricate appropriately
• Check alignment of motor and equipment
• Ensure supply wiring and terminal box and properly sized and
installed
• Provide adequate ventilation
Maintenance

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Energy Efficiency Opportunities in Motor1.4EnergyEfficiencyofElectricMotor
• Variable speed drives (VSDs)
• Also called inverters
• Several kW to 750 kW
• Change speed of induction motors
• Can be installed in existing system
• Reduce electricity by >50% in fans and pumps
• Convert 50Hz incoming power to variable frequency and voltage:
change speed
• Three types
Speed Control of Induction Motor

43. GREEN PRODUCTIVITY
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Energy Efficiency in Electrical Motor
Training Session on Energy Audit
Practitioner
THANK YOU
FOR YOUR ATTENTION
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