Electromagnetic Waves (EX-603 (C)) - Unit 3 Short Notes

UNIT 3: UTILIZATION OF ELECTRICAL ENERGY & ENERGY CONSERVATION

1.0 FUNDAMENTALS OF ILLUMINATION & LIGHTING DESIGN (High Frequency)

1.1 Laws of Illumination

• Inverse Square Law: Illuminance $E$ (lux) from a point source is inversely proportional to the square of the distance $d$ (m) from the source.

$$E = \frac{I}{d^2}$$

where $I$ = candle power (candela, cd). \boxed{E = I/d^2}

• Lambert's Cosine Law: Illuminance on a surface is proportional to the cosine of the angle of incidence $\theta$.

$$E = \frac{I \cos\theta}{d^2}$$

[!TIP] For a horizontal surface, $\theta$ is the angle between the normal to the surface and the line joining source to point.

• Combined Law: For a source at height $h$ above a horizontal plane, illuminance at a point at horizontal distance $r$ is:

$$E = \frac{I \cos^3\phi}{h^2}$$

where $\phi$ is the angle of elevation, $$\displaystyle \cos\phi = h/\sqrt{h^2+r^2} $$.

1.2 Lighting Scheme Design & Calculations

• Key Factors:

  • Task requirements (illuminance level, uniformity)

  • Room dimensions, surface reflectances (ceiling, walls, work plane)

  • Mounting height $h$, spacing $S$

  • Lamp type, luminous efficacy ($\Phi/W$)

  • Utilization Factor (UF): Ratio of lumens reaching work plane to total lumens emitted by lamps. Depends on room cavity ratio.

  • Maintenance Factor (MF): Accounts for lamp depreciation and dirt. $$\displaystyle MF = 0.7 $$ to $0.9$ typically.

  • Space-Height Ratio (SHR): $$\displaystyle SHR = S/h $$. Used for uniform spacing; typical values 0.5–1.5.

• Number of Lamps:

$$N = \frac{E \times A}{UF \times MF \times (\Phi/W)}$$

where $E$ = required illuminance (lux), $A$ = area (m²), $\Phi/W$ = luminous flux per watt (lm/W).

• Illumination Calculation:

  • Point-by-point: Use inverse square & cosine laws for each source, sum contributions.

  • Average: $$\displaystyle E_{avg} = \frac{N \times UF \times MF \times (\Phi/W)}{A} $$.

• [!CAUTION] Ensure all units consistent: $E$ in lux, $A$ in m², $\Phi/W$ in lm/W.

1.3 Types of Lighting Schemes & Lamps

• Classification by Distribution:

  | Scheme | % Downward | % Upward | Application | |--------|------------|----------|-------------| | Direct | 90–100% | 0–10% | Factories, offices | | Indirect | 0–10% | 90–100% | Cinemas, archives | | Semi-direct | 60–90% | 10–40% | Homes, hospitals | | General | 40–60% | 40–60% | Classrooms, halls |

• Energy-Efficient Lamps:

  • LED: Efficacy 100–200 lm/W, life 50,000 h, instant start.

  • CFL: Efficacy 50–70 lm/W, life 8,000–10,000 h, contains mercury.

  • Fluorescent: Efficacy 40–100 lm/W, requires ballast.

  • Sodium Vapor: High efficacy (100–150 lm/W), monochromatic (yellow).

• Comparison: LED > CFL > Fluorescent > Incandescent in efficacy, life, and heat emission.

2.0 ELECTRICAL HEATING & WELDING TECHNOLOGIES (High Frequency)

2.1 Electric Heating Methods

• Advantages: Clean, controllable, high efficiency, no flue gases, safe.

• Losses: Radiation, convection, conduction to supports.

• Resistance Heating:

  • Direct: Current passes through charge (e.g., salt bath furnace).

  • Indirect: Current through separate heating elements (e.g., toaster, oven).

• Induction Heating:

  • Principle: Alternating magnetic field induces eddy currents in conductive material, heating by $$\displaystyle I^2R $$.

  • Applications: Melting, hardening, soldering.

  • Limitations: Works only on conductors, expensive equipment, skin effect limits penetration.

  • High-Frequency Induction Furnace Types:

    • Coreless (crucible): For melting metals.

    • Channel: For holding and superheating.

    • Vertical crucible: For large melts.

• Dielectric Heating:

  • High-frequency electric field causes molecular friction in non-conductors (e.g., wood, plastics).

  • Used for drying, welding plastics.

2.2 Welding Processes

• Classification:

  | Process | Principle | Examples | |---------|-----------|----------| | Arc Welding | Electric arc melts electrode & base metal | SMAW, GMAW, GTAW | | Resistance Welding | Current passes through joint, heat at contact | Spot, seam, projection | | Gas Welding | Combustion of fuel gas (oxy-acetylene) | Oxy-fuel welding | | Solid-State | Pressure + vibration/friction, no melting | Friction stir, ultrasonic | | Electron Beam | Focused electron beam in vacuum | EBW (deep penetration) | | Laser | Focused laser beam | Laser beam welding |

• Arc Welding: Electrode creates arc; shielded by flux or gas. Types: Stick (SMAW), MIG (GMAW), TIG (GTAW).

• Resistance Welding:

  • Spot: Two electrodes clamp sheets, current pulse.

  • Seam: Rotating wheels for continuous weld.

  • Projection: Localized heating on projections.

• Electron Beam Welding: High-energy electrons in vacuum; deep, precise welds; used in aerospace.

2.3 Welding Equipment

• Welding Transformers:

  • Requirements: High current, low voltage (15–40 V), drooping characteristic (current stable with voltage changes).

  • Types: Rectifier-type (AC to DC), transformer-rectifier.

  • Characteristics: Open-circuit voltage 60–80 V, short-circuit current adjustable.

  • [!TIP] For manual arc welding, drooping V-I characteristic ensures stable arc.

3.0 ELECTROCHEMICAL PROCESSES (Moderate Frequency)

3.1 Laws of Electrolysis (Faraday's Laws)

• First Law: Mass of substance deposited at an electrode is directly proportional to quantity of electricity (charge) passed.

$$W = Z \cdot Q = Z \cdot I \cdot t$$

where $Z$ = electrochemical equivalent (ECE), $I$ = current (A), $t$ = time (s).

• Second Law: For same quantity of electricity, masses of different substances deposited are proportional to their chemical equivalent weights.

$$\frac{W_1}{W_2} = \frac{E_1}{E_2}$$

where $E$ = equivalent weight.

• ECE: $$\displaystyle Z = \frac{E}{F} $$, $F$ = Faraday constant = 96,500 C/mol.

  \boxed{W = I \cdot t \cdot \frac{E}{96500}} (mass in grams if $E$ in g/equivalent).

3.2 Electroplating & Electroforming

• Electroplating: Deposit thin metal layer for corrosion resistance, appearance, conductivity.

• Electroforming: Produce thick metal parts by building up on a mandrel (later removed).

• Calculation Example:

  Given: $$\displaystyle I = 3 $$ A, $$\displaystyle t = 30 $$ min = 1800 s, $$\displaystyle Z = 0.065 $$ mg/A·s (or 0.000065 g/A·s).

  $$\displaystyle W = 3 \times 1800 \times 0.000065 = 0.351 $$ g.

3.3 Electrolytic Processes

• Electro-refining: Impure anode dissolves, pure metal deposits at cathode (e.g., copper refining).

• Anodizing: Electrochemical oxidation of aluminum to form protective oxide layer.

4.0 TRACTION SYSTEMS & ELECTRIC VEHICLES (High Frequency)

4.1 Electric Traction Fundamentals

• DC Series Motor Suitability:

  • High starting torque ($$\displaystyle T \propto I_a^2 $$).

  • Speed varies with load (soft characteristic): heavy load → slow speed, automatic load sharing in multiple units.

  • Simple, robust, regenerative braking possible.

• Types of Electric Drives:

  • Group drive: One motor drives multiple axles via shaft/coupling (less flexible).

  • Individual drive: Each axle has its own motor (better adhesion, control).

• Key Parameters:

  • Dead weight: Total weight of locomotive/train.

  • Acceleration weight: Portion of dead weight contributing to traction effort.

  • Train resistance: Sum of rolling, gradient, curve resistances (N/tonne).

4.2 Speed-Time Curves & Motion Equations

• General Speed-Time Curve (Main Line Service):

  DiagramCANVAS: Trapezoidal speed-time curve with acceleration, constant speed, retardation periods. Label axes: speed (km/h) vs time (s), show areas as distances.

• Trapezoidal Curve Assumptions: Constant acceleration $\alpha$, constant retardation $\beta$, constant speed $$\displaystyle V_m $$.

• Derivation of Maximum Speed:

  Let $$\displaystyle t_a $$ = acceleration time, $$\displaystyle t_r $$ = retardation time, $$\displaystyle t_c $$ = constant speed time, $D$ = total distance (m).

  Acceleration: $$\displaystyle V_m = \alpha t_a $$ → $$\displaystyle t_a = V_m/\alpha $$

  Retardation: $$\displaystyle V_m = \beta t_r $$ → $$\displaystyle t_r = V_m/\beta $$

  Distances:

$$d_a = \frac{1}{2} \alpha t_a^2 = \frac{V_m^2}{2\alpha}, \quad d_r = \frac{V_m^2}{2\beta}, \quad d_c = V_m t_c$$

Total distance:

$$D = \frac{V_m^2}{2}\left(\frac{1}{\alpha} + \frac{1}{\beta}\right) + V_m t_c$$

If total time $T$ is given: $$\displaystyle T = t_a + t_c + t_r = V_m\left(\frac{1}{\alpha} + \frac{1}{\beta}\right) + t_c $$.

Solve for $$\displaystyle V_m $$:

\boxed{V_m = \frac{-\left(\frac{1}{\alpha}+\frac{1}{\beta}\right) + \sqrt{\left(\frac{1}{\alpha}+\frac{1}{\beta}\right)^2 + \frac{8D}{T?}}} Wait, correct from D equation:

Rearranging: $$\displaystyle \frac{V_m^2}{2}\left(\frac{1}{\alpha}+\frac{1}{\beta}\right) + V_m t_c - D = 0 $$. Solve quadratic in $$\displaystyle V_m $$.

[!TIP] For simple trapezoid with $$\displaystyle t_c=0 $$ (triangular curve), $$\displaystyle V_m = \sqrt{2D\left(\frac{\alpha\beta}{\alpha+\beta}\right)} $$.

• Parameters:

  • Average speed: $$\displaystyle V_{avg} = D / T $$

  • Specific energy consumption (Wh/tonne-km): Energy consumed per tonne per km.

4.3 Electrical Braking Methods

• Plugging (Reverse Current): Motor connections reversed; acts as brake but dissipates energy as heat in resistors. High stress on motor.

• Rheostatic Braking: Motor acts as generator; energy dissipated in external resistors. Used for deceleration.

• Regenerative Braking: Generated energy fed back to supply system. Most efficient, used in EVs and modern trains.

• [!TIP] Regenerative braking requires compatible power supply (e.g., DC bus, grid).

4.4 Electric Vehicles (EV) & Hybrid Vehicles

• EV Components:

  • Electric Motor: AC/DC motor (induction, permanent magnet, BLDC).

  • Battery: Li-ion (high energy density), lead-acid, NiMH.

  • Controller: Inverter (DC-AC) for motor speed/torque control.

  • Transmission: Single-speed reduction gear (EVs); multi-speed for performance.

• Transmission in EVs: Often single-speed due to wide torque-speed range of electric motors.

• Hybrid Vehicle Types:

  • Series Hybrid: Engine drives generator; motor drives wheels.

  • Parallel Hybrid: Both engine and motor can drive wheels.

  • Series-Parallel: Combines both (e.g., Toyota Prius).

• Advantages: Reduced emissions, lower operating cost, regenerative braking.

• Challenges: Battery cost, range anxiety, charging infrastructure.

4.5 Load Equalization

• Need: Traction motors draw high current during acceleration, causing voltage drops and stress on supply. Load equalization smooths demand.

• Methods: Use of inertia (flywheel) or central battery/motor-generator set to supply peak currents. During acceleration, stored energy supplements supply; during braking, energy stored back.

5.0 ENERGY MANAGEMENT FUNDAMENTALS (Very High Frequency)

5.1 Energy Audit

• Definition: Systematic examination of energy use and flows to identify conservation opportunities.

• Types:

  • Preliminary Audit: Walk-through, identifies obvious savings.

  • Detailed Audit: In-depth measurement, data logging, analysis.

  • Targeted Audit: Focus on specific systems (e.g., HVAC, compressed air).

• Significance: Reduces costs, improves efficiency, environmental impact, compliance.

• Steps:

  1. Planning & team formation.

  2. Data collection (energy bills, equipment inventory).

  3. Walk-through survey.

  4. Detailed measurement & analysis.

  5. Identify Energy Conservation Opportunities (ECOs).

  6. Prepare report with recommendations and ROI.

  7. Implementation & monitoring.

5.2 Energy Manager Role

• Responsibilities:

  • Develop energy policy and plans.

  • Conduct audits and implement ECOs.

  • Monitor energy consumption.

  • Train staff on energy awareness.

  • Ensure compliance with regulations.

• Qualities: Technical knowledge, analytical skills, communication, project management.

• Functions: Planning, organizing, controlling, motivating energy conservation.

5.3 Thermodynamics in Energy Conservation

• First Law (Energy Conservation):

$$\Delta U = Q - W$$

Energy cannot be created/destroyed; input = output + accumulation.

Example: In a boiler, heat input from fuel = steam output + losses (flue gases, radiation).

• Second Law (Entropy Principle):

  • Entropy of isolated system never decreases; $\Delta S \geq 0$.

  • Heat cannot spontaneously flow from cold to hot.

  • Significance: No process 100% efficient; sets maximum efficiency (Carnot).

  • Example: Carnot efficiency $$\displaystyle \eta_{max} = 1 - T_c/T_h $$. Real engines always lower.

5.4 Demand Side Management (DSM)

• Load Curve Analysis: Plot of power demand vs time. Identifies peak/off-peak periods.

  [!TIP] Aim to flatten curve: reduce peaks, fill valleys.

• DSM Techniques:

  | Technique | Description | Example | |-----------|-------------|---------| | Peak Clipping | Reduce demand during peaks | Turn off non-essential loads | | Valley Filling | Increase off-peak demand | Storage heating, EV charging | | Load Shifting | Move load from peak to off-peak | Shift industrial processes | | Energy Efficient Equipment | Reduce overall demand | LED lighting, efficient motors |

• Differences: Peak clipping reduces max demand; valley filling increases min load; load shifting relocates demand.

5.5 Energy Policy & Housekeeping

• Energy Policy: Formal statement of commitment to conservation; sets targets, responsibilities.

  Example: "All new buildings must have LED lighting and solar water heating."

• Energy-Efficient Housekeeping:

  • Regular maintenance (cleaning, lubrication).

  • Switching off idle equipment.

  • Optimizing HVAC schedules.

  • Employee training and awareness.

  • Low-cost, high-impact measures.

6.0 ENERGY EFFICIENCY IN ELECTRICAL SYSTEMS (High Frequency)

6.1 Energy-Efficient Motors

• Differences from Standard Motors:

  • Higher efficiency (IE3/IE4 vs IE1/IE2).

  • Better materials (thin laminations, high-grade steel).

  • Optimized design (reduced losses: copper, core, friction).

  • Often larger size for lower current density.

• Selection Criteria: Load profile (efficiency peak at expected load), life-cycle cost (not just purchase price), environment (duty cycle).

• Importance: Motors consume ~60% of industrial electricity; even 1% efficiency gain saves significant energy.

6.2 Power Factor Improvement

• Causes of Poor PF:

  • Inductive loads (motors, transformers) draw lagging current.

  • Overloading, underloading.

  • Harmonic currents.

• Disadvantages:

  • Increased current → higher $$\displaystyle I^2R $$ losses.

  • Reduced system capacity (transformers, cables).

  • Voltage drop, poor voltage regulation.

  • Penalty charges from utilities.

• Improvement Methods:

  • Static Capacitors: Connect in parallel (shunt) to supply leading current. Most common.

  • Synchronous Motors: Operate at leading PF; can also provide mechanical power.

  • Phase Advancers: For induction motors, improve PF by injecting leading current into rotor circuit.

  • High-PF Lamps: Use electronic ballasts.

• [!TIP] Capacitor banks should be placed near load for maximum benefit.

6.3 Variable Speed Drives (VSD)

• Principle: Adjust motor speed to match load requirement, instead of throttling (dampers, valves).

  • For centrifugal loads (fans, pumps), affinity laws: $$\displaystyle P \propto N^3 $$, $Q \propto N$.

  • Reducing speed by 20% can cut power by ~50%.

• Energy-Saving Applications: HVAC fans, pumps, compressors, conveyors.

• Types: VFD (voltage frequency drive), VSD for DC motors.

6.4 Predictive & Preventive Maintenance

• Predictive Maintenance: Condition-based (vibration, thermography, oil analysis) to predict failures before they occur.

• Preventive Maintenance: Scheduled maintenance (cleaning, lubrication, parts replacement) at fixed intervals.

• Role in Energy Auditing: Poorly maintained equipment has higher energy consumption (e.g., dirty heat exchangers, misaligned belts).

• Benefits: Reduced downtime, extended equipment life, energy savings (5–20%), lower repair costs.

• Comparison:

  | Aspect | Preventive | Predictive | |--------|------------|------------| | Basis | Time/usage | Condition | | Cost | Lower initial, higher ongoing | Higher initial, lower ongoing | | Effectiveness | May replace good parts | Targets actual need |

7.0 INDUSTRIAL ENERGY CONSERVATION CASE STUDIES (High Frequency)

7.1 Cogeneration (Combined Heat & Power)

• Principle: Generate electricity and useful thermal energy (steam/heat) from same fuel source.

• System Configurations:

  • Back Pressure Turbine: Steam expanded to process pressure; no condenser. Simple, high thermal efficiency.

  • Extraction-Condensing Turbine: Steam extracted at intermediate pressure for process; remaining expanded to condenser. Flexible.

  • Double Extraction Back Pressure: Two extraction points for different temperature processes.

  DiagramCANVAS: Schematic of each configuration with turbine, generator, condenser, process steam lines.

• Benefits: Overall efficiency 70–90% (vs 30–40% for separate generation), reduced fuel cost, lower emissions.

7.2 Waste Heat Recovery

• Techniques:

  • Heat Exchangers: Recover heat from exhaust gases, cooling water (shell-and-tube, plate).

  • Waste Heat Boilers (WHB): Generate steam from hot flue gases (e.g., in steel plants, kilns).

  • Thermal Wheel/Regenerator: Rotary heat exchanger for air streams.

• Applications:

  • Preheating combustion air or feed water.

  • Drying processes.

  • Space heating.

• Need & Benefits: Reduces fuel consumption, lowers emissions, improves process efficiency.

7.3 Industry-Specific Conservation Processes

• Sugar Industry:

  • Energy-Intensive: Juice extraction, evaporation, crystallization.

  • Conservation:

    • Use bagasse (fibrous residue) for cogeneration (high-pressure boilers).

    • Multiple Effect Evaporators with vapor recompression.

    • Trap systems to recover condensate.

    • Efficient drives for mills (VSDs).

• Cement Industry:

  • Major Consumption: Kiln (clinker production), preheater, grinding.

  • Conservation:

    • Preheater/Precalciner: Recover heat from kiln exhaust to preheat raw meal.

    • Waste heat recovery from cooler and kiln exhaust for power generation.

    • High-efficiency fans and VSDs for gas handling.

    • Optimized grinding (vertical roller mills vs ball mills).

• Textile Industry:

  • Energy-Intensive: Spinning, weaving, dyeing, drying (stenters).

  • Conservation:

    • Waste heat recovery from stenters (heat exchangers for preheating combustion air).

    • Energy-efficient motors and VSDs for pumps/compressors.

    • LED lighting in large floors.

    • Optimized process scheduling to avoid peak tariffs.

• Agriculture Waste Utilization:

  • Biomass Energy: Direct combustion, gasification, anaerobic digestion (biogas).

  • Applications: Drying crops, water pumping, electricity generation.

  • Benefits: Renewable, reduces fossil fuel use, waste disposal solution.

7.4 Conservation in Buildings & HVAC

• Electrical Conservation:

  • Lighting: LED, occupancy sensors, daylight harvesting.

  • HVAC: VSDs on fans/pumps, zonal control, economizer cycles.

  • Equipment: Energy Star rated, power management.

• Thermal Energy Audit in AC:

  • Assess cooling load (heat gain from conduction, radiation, occupants, equipment).

  • Evaluate chiller/compressor efficiency (COP), refrigerant charge, duct losses.

  • Recommend: better insulation, variable refrigerant flow (VRF), thermal storage.

• Electrical Load Calculation for AC:

  • Cooling load $Q$ (W) = sum of sensible + latent heat gains.

  • Total power $$\displaystyle P = Q / COP $$ (coefficient of performance).

  • Include safety factor (1.1–1.2).

8.0 ECONOMIC ANALYSIS FOR ENERGY PROJECTS (Moderate Frequency)

8.1 Project Evaluation Methods

• Payback Period:

  • Time to recover initial investment from annual savings.

$$\text{Payback} = \frac{\text{Initial Investment}}{\text{Annual Savings}}$$

• Advantages: Simple, intuitive.

• Limitations: Ignores time value of money, cash flows after payback.

• Cost-Benefit Analysis (CBA):

  • Compare present value of benefits vs costs over project life.

  • Include risk analysis: sensitivity to fuel price, load variations.

• Inflation Risk Analysis:

  • Adjust future cash flows for inflation.

  • Use nominal vs real discount rates.

8.2 Depreciation

• Purpose: Allocate cost of asset over useful life; tax benefit.

• Methods:

  • Straight Line Method (SLM):

$$\text{Annual Depreciation} = \frac{\text{Cost} - \text{Salvage Value}}{\text{Useful Life}}$$

Book value decreases linearly.

• Written Down Value (WDV) Method:

$$\text{Depreciation} = \text{Book Value at Start} \times \text{Depreciation Rate}$$

Book value decreases geometrically; higher depreciation initially.

• Comparison:

  | Feature | SLM | WDV | |---------|-----|-----| | Depreciation | Constant | Decreasing | | Book Value | Linear decline | Exponential decline | | Tax Benefit | Lower initially | Higher initially |

8.3 Financial Metrics

• Simple Rate of Return (SRR):

$$\text{SRR} = \frac{\text{Average Annual Profit}}{\text{Initial Investment}} \times 100\%$$

• Net Present Value (NPV):

$$\text{NPV} = \sum_{t=1}^{n} \frac{C_t}{(1+r)^t} - C_0$$

where $$\displaystyle C_t $$ = net cash flow year $t$, $r$ = discount rate, $$\displaystyle C_0 $$ = initial cost.

• Accept project if NPV > 0.

• [!TIP] NPV accounts for time value of money; preferred over payback.

9.0 SUPPORTING TOOLS, TECHNIQUES & TARIFFS (Moderate Frequency)

9.1 Energy Auditing Instruments

• Power Analyzer: Measures voltage, current, power, PF, harmonics.

• Thermography (Infrared Camera): Detects hot spots (electrical faults, insulation leaks).

• Combustion Analyzer: Flue gas analysis (O₂, CO, CO₂) for boiler efficiency.

• Lux Meter: Illuminance measurement.

• Anemometer: Air velocity for HVAC ducts.

• Ultrasonic Flow Meter: Liquid flow without intrusion.

• Data Logger: Records parameters over time.

9.2 Load Management & Tariffs

• Tariff Types:

  • Flat Rate: Fixed charge per unit.

  • Block Rate: Increasing blocks (higher rates for higher consumption).

  • Time-of-Day (TOD): Different rates for peak, normal, off-peak hours.

  • Two-Part: Fixed charge + energy charge.

  • Demand Charge: Based on maximum demand (kVA/kW).

• Restructuring for Conservation:

  • Higher peak tariffs to discourage peak usage.

  • TOD tariffs to shift load to off-peak.

  • Incentives for energy-efficient equipment.

9.3 Analysis & Visualization Tools

• Load Energy Balance Diagram: Sankey diagram showing energy inputs, useful output, losses.

• Material Load Energy Balance Diagram: Includes material flows with energy content.

• Energy Flow Networks: Graphical representation of energy streams in a system.

• Matrix Charts: Relationship between energy forms, equipment, processes.

• Simulation & Modeling:

  • Purpose: Predict performance of ECOs, optimize systems.

  • Tools: DOE-2 (buildings), MATLAB/Simulink (industrial processes).

  • [!TIP] Use simulation to test "what-if" scenarios before implementation.

10.0 ADDITIONAL TOPICS (Lower Frequency but Covered)

10.1 Lubrication and Tribo-logical Innovations

• Energy Saving via Lubrication:

  • Reduces friction → lower motor load → energy savings.

  • Use high-quality, correct viscosity lubricants.

  • Synthetic oils: better temperature stability, longer life.

• Tribo-innovations:

  • Surface coatings (e.g., DLC, PTFE) to reduce friction.

  • Magnetic bearings (eliminate lubrication, reduce friction).

  • Optimized surface textures.

10.2 Calculation Problems

• Illumination (Multiple Point Sources):

  • Sum illuminance from each source at point: $$\displaystyle E_{total} = \sum \frac{I_i \cos\theta_i}{d_i^2} $$.

• Heating Element Power:

  • Series: $$\displaystyle P = V^2/(R_1+R_2) $$.

  • Parallel: $$\displaystyle P = V^2 \left(\frac{1}{R_1} + \frac{1}{R_2}\right) $$.

• Electrochemical Deposition:

  $$\displaystyle W = I \cdot t \cdot \frac{E}{96500} $$ (grams).

• Traction:

  • For trapezoidal curve: use derived equations for $$\displaystyle V_m $$, $$\displaystyle t_a $$, $$\displaystyle t_r $$, $$\displaystyle d_a $$, $$\displaystyle d_r $$, $$\displaystyle d_c $$.

  • Specific energy consumption: $$\displaystyle \text{Wh/tonne-km} = \frac{\text{Energy consumed (Wh)}}{\text{Train weight (tonne)} \times \text{Distance (km)}} $$.

EXAM STRATEGY:

1. Illumination & Lighting: Master inverse square & cosine laws; practice UF/MF calculations.

2. Traction: Derive trapezoidal curve equations; know DC series motor traits.

3. Energy Management: Energy audit steps, DSM techniques, thermodynamics laws.

4. Case Studies: Focus on sugar, cement, textile conservation measures.

5. Numericals: Be unit-consistent; box final formulas.

Common Pitfalls: Confusing UF with MF; forgetting to convert units (min→s, km/h→m/s); misapplying affinity laws for VSDs.