The document discusses opportunities for energy conservation in electrical equipment and auxiliaries at power plants. It identifies high energy consuming equipment like motors, pumps, fans and transformers. It recommends installing variable frequency drives for fans and pumps to reduce energy consumption as their loads vary continuously. Installing energy efficient motors and new technologies can help optimize equipment efficiency and reduce energy losses. Proper sizing, maintenance and eliminating issues like voltage imbalances and harmonics are also suggested for improved motor performance.

1. Energy Audit & Energy
Conservation
Opportunities in
Electrical Equipments /
Auxiliaries
Manohar Tatwawadi
Director, tops.
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2. Electrical Equipments / Auxiliaries
PUMP, FAN,
MILL MOTORS
HT MOTORS
LT MOTORS
TRANSFORMERS
HT
TRANSFORMERS
LT
TRANSFORMERS
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3. HT MOTORS
• Induced Draft Fan Motors
• Forced Draft Motors
• Primary Fan Motors
• Coal Mill Motors
• BFP Motors
• Condensate Extraction Pump Motor
• Circulating water Pump Motors….. etc.
• The Total HT Aux. consume about 6 to 7% of
Generation.
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4. LT Motors
• Air preheater Motors
• Ash handling plant Motors
• Coal Handling Plant (HT & LT) Motors
• Air compressors
• Cooling water pump Motors
• WT Plant Motors
• The total LT Aux equipment may consume 1%
to 1.5% of the total load.
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5. Design capacity and Operating Range
for HT Pumps/Motors/Fans
S.N. Equipment Parameter Design Operating
1 Boiler Feed Pump Flow 79.7 % 71 – 91%
Pressure 83.23 % 74 – 88%
2 Condenser Extraction
Pump
Pressure 87.8% 85 – 105%
Flow 93.2% 70 – 98%
3 Induced draft fan Pressure 52.1% 45 – 95%
Flow 65.4% 70 – 79%
4 Forced Draft fan Pressure 55.6% 33 – 51%
Flow 77% 60 – 68%
5 Primary Air Fan Pressure 69.2% 69 – 79%
Flow 74.3% 40 – 61%
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6. Reasons for high Aux Consumption
• Plant Specific Factors: design deficiencies,
technology, lack of inst. & control, forced
outages, operational practices / constraints
• External Factors:- Fuel shortages, quality,
higher loading of ESP, Ash handling system
• Grid Specific Factors: Backing down of units,
Reactive power generation
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7. Loading of ID, FD, PA fans
• Illegal Furnace Air Ingress
• APH air leakage
• Debris in flue gas duct
• ID fan /Motor maintenance
• Oversized Motors etc.
• Increased Pressure drop across APH.
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8. Energy Conservation Measures
• New Technology Adoption such as
• Use of VFD for Fans for ID Fans as the load is
continuously varying between 65 – 75%.
• The installation of VFDs for ID Fans will reduce
the energy consumption around 5.3 MU per
year for one 210 MW unit with a payback
period of less than 3 Years.
• When motor cooling is provided as in the case
of BFP the coolers must be serviced and
maintained.
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9. Variable Frequency Drive
• AC 50 Htz power converted to DC in the rectifier
unit.
• DC power is then converted to Controlled
variable frequency AC Power by an inverter
using Thyristors.
• Output voltage is varied by changing the width
and polarity of switched pulses, whereas the
output frequency is adjusted by changing the
switching cycle time.
• This AC drives the variable speed motor.
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10. Variable Frequency Drives
• During starting of VFD normally low freq and volt is
applied to the motor. So the High starting current is
reduced. This is known as soft start.
Input Power
Operators
Interface
Variable
Frequency
controller
Variable
Frequency
Power
A.C. Motor
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11. Various applications for VFD
• ID Fans .. To control draft
• FD Fans … to control air supply
• Coal Feeders…. To control Coal supply
• Cooling water Pumps …. To control CW supply to
condenser
• Cooling Tower Fans…. To control CW inlet Temp.
• Cond Extr Pumps… to control Condenser level
• Boiler Feed Pump … to control Boiler Drum Level.
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12. Advantages of VFD
• Smooth Control of Flue gas.
• Absence of Limitation of number of starts.
• No Voltage dips in the system
• Increased efficiency over wide operating
speed range.
• Increased life of motors due to soft starts.
• Simple arrangements for cooling of Hydraulic
Coupling
• Reduction in size of unit/station Transformer.
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13. VFD For Boiler Feed Pumps
• The load on BFP is also continuously varying
and is about 2 to 2.5% of the Generation
• The installation of VFD will reduce the energy
consumption by around 13.8 MU per year per
210 MW Plant and the payback period upto 3
to 3.5 years.
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14. Steam driven BFPs
• The efficiency of conversion of the plant can
be increased from 33 to 35%.
• Equivalent power of about 7 MW in case of a
210 MW unit can be released to the grid.
• Better controllability as compared to Electric
Motor.
• Savings can be achieved at part load also.
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15. Mill Motors
• Variation in speed not required
• Motor currents vary due to variations in Coal,
Air.
• Restrict the input coal size.
• Increased DP across Mill will increase Mill
power.
• Coal fineness also affects the loading of the
mill.
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16. LT Auxiliaries - Motors
• Magnetic Losses: Dependent on the thickness
of the core stampings, applied voltage and
frequency.
• Copper Losses: Sensitive to the current flow in
the motor winding, quality of power supply
i.e. unbalanced voltage, voltage variations,
harmonics, winding temp etc.
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17. Voltage unbalance
• The design of the 3 Phase motor calls for a 3
phase balanced supply. The unbalance leads
to flow of additional negative sequence
currents in motors resulting in rise in the temp
of the windings.
• This will reduce the motor capacity.
• The operation of motor above 5% un balance
is not recomended
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18. Variation of motor current and losses
Voltage Unbalabce
IncreasedUnbalanceCurrents
andLossesin%
0.0 1.0 2.0 3.0 4.0 5.0
05
10
15
20
25
30
35
Losses
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19. Voltage Variation
• At reduced input voltage, the motor output
will reduce and the losses will increase.
• The copper losses will increase by square of
∆ V.
• The torque is proportional to the square of
Voltage and is proportional to the slip.
• When voltage decreases, the torque
decreases and for maintaining the torque
the slip increases and speed falls.
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20. Harmonics
• Harmonic currents depending on their frequency
will cause additional rotating magnetic fields in
the motor.
• These magnetic fields rotate in the same
direction or in opposite direction based on the
frequencies.
• The magnetic field created by 5th, 11th , 17th, 23rd
.. Is negative phase sequence and will cause
reverse torque. Other even harmonics also cause
more losses in the motor.
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21. Harmonics
• Voltage harmonics cause increase in iron
losses.
• Current harmonics cause increase in winding
losses.
• Harmonics can be suppresses by use of
necessary filters along with voltage stabilizers.
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22. Starting Characteristics
• For Direct starters the starting current is about
5 to 6 times the full load current.
• For star-delta starter the starting current is
approx 2 – 3 times the full load current.
• Star Delta starters are preferred when large no
of motors are to be started within a short
period of time.
• Delstar starters work as star delta starter
during startup and will convert to delta.
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23. Load Factor
• All the motors are designed for maximum
efficiency at full load.
• As the load factor decreases, motor efficiency
decreases.
• Idle running of motors consume power and
reduce power factor.
• Cost benefit analysis can be done for such
cases and appropriate motor sizing can be
done.
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24. Speed and Duty Cycle
• For the same input power motors with higher
speed have a higher efficiency and high power
factor at rated load than lower speed motors.
• When the load varies with large nos of starts
and stops. To minimise the energy loss, the
duty cycle must be matched with the intended
duty
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25. Motor rewindings
• While rewinding, sometimes the motor
assembly is heated for easy removal of
windings. This may damage the varnish
between the stampings of the stator core and
may increase the eddy currents.
• This may also cause the reduction in thickness
of the core and reduction in resistance of
magnetic path causing more eddy current
loss.
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26. Energy Conservation Measures
• Voltage variation:- at 10% voltage drop the
torque reduces by 19% , current increases by
11% of Full load Current and efficiency
reduces by 1.1%.
• Unbalanced voltage:- Evenly distribute the
load in three phases.
• Due to single phasing the capacity will reduce
to half, in star two phases overloaded, in delta
one winding is overheated.
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27. Energy conservation measures
• Check up for bearing cooling systems.
• Set up filters and stabilizers for harmonics if
necessary.
• Use of starters for soft starts.
• Use higher speed motors wherever possible.
• Use proper duty cycle motors.
• Checkup the failures of the rewound motors
and conductor sizes in original motors. Etc.
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28. Transformers Iron losses
• Eddy current and
• Hysteresis loss
• Above losses due to idle charging, oversizing,
use of inferior core material, harmonics in the
distribution system etc.
• Metal glass (Amorphus) cores reduce the core
loss by 75%
• Cost about 2 times, payback period 2years.
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29. Suggested Measures
• Standby Transformers may be de-energized on
primary side.
• Increase the load factor to max if possible.
• Use methods for suppressions of harmonics
by using filters.
• Effective cooling of transformer: Sludge
formation in the oil, more acidity content of
oil, presence of dissolved gasses in oil.
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30. Tips for Energy Conservation for
IndustriesMotors
• Properly size to the load for optimum efficiency.
(High efficiency motors offer of 4 - 5% higher efficiency than standard
motors)
• Use energy-efficient motors where economical.
• Use synchronous motors to improve power factor.
• Check alignment.
• Provide proper ventilation (For every 10 oC increase in motor operating
temperature over recommended peak, the motor life is estimated to be
halved)
• Check for under-voltage and over-voltage conditions.
• Balance the three-phase power supply. (An imbalanced voltage can reduce
3 - 5% in motor input power)
• Demand efficiency restoration after motor rewinding. (If rewinding is not
done properly, the efficiency can be reduced by 5 - 8%)
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31. Tips for Energy Conservation for
Industries
Drives
• Use variable-speed drives for large variable loads.
• Use high-efficiency gear sets.
• Use precision alignment.
• Check belt tension regularly.
• Eliminate variable-pitch pulleys.
• Use flat belts as alternatives to v-belts.
• Use synthetic lubricants for large gearboxes.
• Eliminate eddy current couplings.
• Shut them off when not needed.
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32. Tips for Energy Conservation for
IndustriesFans
• Use smooth, well-rounded air inlet cones for fan air intakes.
• Avoid poor flow distribution at the fan inlet.
• Minimize fan inlet and outlet obstructions.
• Clean screens, filters, and fan blades regularly.
• Use aerofoil-shaped fan blades.
• Minimize fan speed.
• Use low-slip or flat belts.
• Check belt tension regularly.
• Eliminate variable pitch pulleys.
• Use variable speed drives for large variable fan loads.
• Use energy-efficient motors for continuous or near-continuous operation
• Eliminate leaks in ductwork.
• Minimise bends in ductwork
• Turn fans off when not needed.30-Jul-19 32total output power solutions

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