Energy Conservation in Electrical Machines

Energy Conservation in Electrical Machines

• Syllabus covers needs for energy conservation in induction motors and transformers, energy conservation techniques, energy efficient equipment, and energy efficient transformers.

Need of Energy Conservation in Induction Motor and Transformer

• Economic growth depends on industrialization and energy consumption.
• Growing energy costs from limited sources necessitate power saving.
• Three-phase induction motors consume about 70% of industrial electricity.
• Earlier motor designs focused on initial cost over energy consumption.
• Modern motors should be energy efficient due to rising energy costs.
• Manufacturers use better materials and designs to improve motor efficiency.
• Energy-efficient motors offer better efficiency and power factor, reducing energy consumption.
• "Energy efficient motors" offer higher efficiency, good power factor, and fewer losses.
• Improvements in slot shape increase efficiency and reduce internal losses.
• New motor designs incorporate changes in slot shapes for increased efficiency.

Factors Affecting Motor Efficiency and Minimizing Losses

• Motor performance depends on input power quality.
• Minimize voltage unbalance by distributing single-phase loads across three phases.
• Use harmonic filters to maintain constant frequency and reduce harmonics.
• A motor survey helps determine the correct motor size for replacement based on nameplate data.
• Motors operate most efficiently near full load, so matching motor to load is crucial.
• Operating motors below 40% load leads to poor efficiency; replace with properly sized motors.
• Minimizing idle and redundant running of motors conserves energy.
• Operating delta-connected motors in star mode at light loads (below 30% full load) saves energy.
• Star-Delta changeover switches can be installed for loads that vary.

Rewinding of Motor

• Rewinding electric motors can be cost-effective.
• Be cautious of decreasing efficiency if rewinding is not perfect.
• New technologies can potentially increase motor efficiency during rewinding.
• Insulation damage during heat application can increase eddy current losses.
• Large cross-section wires reduce stator losses.

Energy Efficient Motor (EEM)

• EEM generates the same output power but uses less input power.
• Design improvements in EEMs focus on reducing intrinsic losses.
• Improvements include lower-loss silicon steel, longer core, thicker wires, thinner laminations and smaller air gap.
• India-available EEMs operate with typically 3-4% higher efficiencies.

Periodic Maintenance

• Machine cleaning ensures proper ventilation and cooling.
• Machine alignment ensures belt drives and couplings are set up correctly.
• Bearing lubrication verifies proper lubrication and sealing.
• Condition Assessment: Includes checking for things like vibration and temperature increases
• Performance assessment regularly measures voltage variations leading to high losses if imbalanced.
• Other factors include phase balancing, matching motor in star-mode, using high-quality bearings, small cooling fans, and lower air gap.

Energy Conservation Techniques - Case Studies

• Convert Delta to Wye connection for lightly loaded motors.
• Use APFC or IPSC for better power factor improvement.
• Use cooling fans for the motor.
• In some cases, use low capacity motors.

Energy Conservation in Transformer

• Transformer is a vital power equipment for generation, transmission, and distribution.
• Transformer operating efficiency directly affects the costs and benefits of the power system.
• Losses in electric transformers may account for 40-50% of total transmission/distribution losses.
• Distribution transformer demand is increasing.
• About 10% of power generation capacity is lost in transformers; therefore, energy conservation matters.

Opportunities in Energy Conservation

• Attempts should be made to reduce energy losses in transformer operation within electrical systems.
• Attention to these losses can significantly reduce greenhouse gas emissions.
• Newer transformers can operate up to 99% efficiency.
• Transformers are crucial for supplying power to various consumers.
• Even small positive changes in transformer efficiency lead to noticeable reductions in generation capacity.

Load Sharing

• Load sharing is used to protect transformers against overloading, voltage variation, and high temperatures.
• Load sharing protects against overload conditions.
• Efficiency drops and secondary windings may overheat due to overload.
• Operating additional transformers in parallel reduces load on any specific transformer and helps to protect against overloading.
• Transformer total power loss and reactive power consumption depend on load distribution.
• Proper adjustment of load distribution minimizes transformer power loss and maximizes transformer efficiency.

Parallel Operation

• Parallel operation helps in this process.
• Transformers are in parallel when their primary windings connect to a common supply and secondary to a common load.
• Transformer capacity matters during selection.
• Oversized transformers results in higher investment and no-load losses.
• Power transformers should give maximum efficiency at full load.
• Operators should adjust the number of transformers online with total demand to maximize the loading for the running transformers.

Isolating Techniques

• Isolation means cutting off electrical supply to ensure safety during maintenance.
• An isolator switch must be present to make the transformer maintenance process safe.
• Devices needed are isolation switches, fuse links, and circuit-breakers
• For isolation on 3-phase L.T. supplies, triple pole switches and neutral links are used.

Replacement by Energy Efficient Transformer

• Energy efficient transformers reduce transmission and distribution losses, and new materials help further reduce those losses.
• Amorphous metal transformers exemplify this.
• Benefits include peak load reductions, lower bills, and longer service lives

Periodic Maintenance

• Periodic maintenance is a vital part of loss control activities.
• Improper maintenance can cause the motor to fail which leads to greater inefficiencies.
• Regular maintenance minimizes equipment failure risk and aids in achieving energy efficiency.
• Maintenance includes disconnecting supply, earthing, and authorized personnel.
• The maintenance must also occur without any risk of sparks.

Advantages of energy efficiency transformers

• They have less operating losses.
• Lowered heat generation
• Longer life
• They are more cost effective
• Reduced core size, lowered resistance, and other factors lead to greater efficiencies

More Opportunities for Energy Conservation in Transformers

• Improvements in core materials
• Use of encapsulated dry type transformers
• Use of energy efficient transformers
• Maintain good power quality and reduce losses this way

Reasons for having energy conservation techniques

• Dependace on efficiency for performance
• Reduced efficiency lowers Transformer performance
• Always attempt to improve efficiency
• Try to keep at full load capacity
• Using units in parallel can ensure efficient load distribution to maintain high efficiency.

Energy Conservation Equipment

Soft Starters

• Provides four advantages
• Soft starting is more efficient and reduces wear on mechanical parts
• Motors can be controlled with delivered power and reduce damage to the motor
• Motors can increase ramped up times
• These are generally installed into the three phase areas
• Allows motors to start and stop smoothly

DOL Starters

• Motors can start with jerks
• High maintenance can be required
• Voltage can be negligble
• Starting torque is uncontrolled
• Affects the MD

Advantages of Soft Starters

• System efficiency improves.
• Energy losses in line reduces
• Small voltage drop in operation of motor.
• Power factor improves
• Low starting torque.
• Motor is protected from mechanical stresses.
• Smooth starting operation.
• MD is controlled as current is limited.
• Less mechanical maintenance.
• Saving in operating cost.
• This enables to adjust the play between the gear wheels or stretching driving belts or chains etc.

Variable Frequency Drives

• It changes standard power lines to DC, which provides efficiency
• Power is also increased from 3:1 in the drives
• Cost reliability and physical size is also another advantage

Benefits of VFD

• Energy saving
• Low Cost
• Better process control
• Low maintenance
• Better energy and power factor qualities

Automatic Star-Delta Starter

• Automatic Star Delta Starter saves energy under variable three-phase induction motor load conditions.
• A microcontroller controls Delta Star usage.
• Energy savings can be 25-30% better than using a conversion module.
• Arrangement has lowered current and higher voltage than compared to normal delta modes

Automatic Power Factor Controller (APFC)

• Can improve system power and controls the power factor itself
• Results in better voltage efficiency and lowers the output
• Helps to save money, as typically most motors will be very inefficient and will get worse over time with use

Intelligent Power Factor Controller (IPFC)

• Guarantees better returns on investment for industries using varying loads.
• It also helps to balance other electrical factors, cutting down on cost.

Installing IPFC

• Equipment is better protected
• Lowers wear and tear of contactors
• Switches the system to maintain current and voltage
• Increases efficiency
• Has easy usage

Harmonic Filters

• Used with harmonic loads to better control the system
• Controls the waves that the current draws
• Makes sure all harmonic generation is correct

Transformer Energy Conservation

• Using Transformers economically can make a world of difference for efficiency
• Methods of helping include:
  • Using more energy
  • Switching transformers at high loads
• These methods better load balance transformers and reduce stress
• The results may require newer technologies

Energy Efficient Motors

• Runs 2/4% more efficient as stated before
• Design change is most likely present
• More efficient materials are used
• Better designs and better capabilities.

Speciality of this Motor

Improved performance by motors increases as designs get better, focus on intrinsic motor losses, and implement better core.

The Differences When Losses Are Minimised

• Using better core materials, steel and other materials

Stray and Rotor I2R losses

• The copper being reduced
• Better materials Friction and windage design is also improved

Positive features of Energy Efficiency

• Torque and energy is high
• Can withstand different temperatures
• Have little resistance

Factors Affecting Energy Efficiency

• Voltage and frequency variation causes resistance
• Many other loads affect balance
• Rewinding and other factors are usually more damaging