Module-1

Page 1: Introduction to Electrical Theory

• Course Code: CE 228

• Module Title: Engineering Utilities 1 - Electrical Theory.

Page 2: Quizzes and Problem Solving

• Assessment Format:

  • Quiz 1: Problem Solving (Short & Long)

  • Quiz 2: Presentation

Page 3: Phenomenon of Electricity

Classical Theory

• Flow of Electrons:

  • Electrons in inner shells: high attraction to nucleus, not easily released.

  • Electrons in outer shells: weaker attraction, more easily freed.

  • Energy addition can elevate electrons to higher shells; excessive energy can expel a valence electron, making it a free electron that contributes to electrical current flow.

Modern Theory

• Flow of Charged Particles:

  • Electricity involves subatomic particles with positive or negative charges.

  • Only charged particles interact with electricity.

  • The electromagnetic force governs the flow of these particles, overcoming gravitational forces.

Law of Charges

• Opposite charges attract; like charges repel.

• Atoms with equal electrons and protons are neutral; imbalances lead to ions.

  • Positive ions: fewer electrons than protons.

  • Negative ions: more electrons than protons.

Page 4: Electrical Current

• Definition: Flow of electric charge through a conductor.

• Direction of flow: Negatively charged particles move from a negative to positive charge.

• Speed of Flow: Actual particle movement is slow (~0.5 inches/sec), but the effect travels at light speed (~186,000 miles/sec).

Page 5: Producing Current Flow

• Methods to Generate Current:

  1. Static Electricity: Created by friction between materials, freeing surface electrons.

  2. Thermoelectricity: Created by heating dissimilar metals (thermocouples).

  3. Piezoelectricity: Generated when pressure deforms certain crystals, causing electron movement.

  4. Electrochemistry: Produced from chemical reactions in solutions.

  5. Photoelectricity: Caused by light photons freeing electrons in materials.

  6. Magnetoelectricity: Generated by moving conductors through magnetic fields causing electron flow.

Page 6: Conductors, Insulators, and Semiconductors

• Conductors: Materials that allow electrical current flow with minimal resistance.

• Insulators: Materials that resist electricity movement, retaining electrons on their atoms (e.g., rubber, glass).

• Semiconductors: Materials that behave as insulators at low temperatures and conductors when heated (e.g., silicon).

Page 7: Units of Electricity

Key Definitions

• Voltage (V): Electrical pressure; higher voltage = increased current flow.

• Current (A): Rate of charge flow, measured in amperes (1 A = 1 coulomb/second).

• Resistance (Ω): Depends on conductor length, diameter, material type, and temperature. (Ohm’s Law: E=IR)

• Power (W): Rate of energy transfer (P=EI).

• Energy (Wh): Power consumed over time (q=Pt).

Page 8: Sample Problem

American Wire Gauge (AWG)

• Conductors’ resistance varies inversely with AWG number.

  • #12 AWG copper:

    • 100 ft: R = 0.162Ω

    • 500 ft: R = 0.810Ω

  • #10 AWG copper:

    • 100 ft: R = 0.102Ω

    • 500 ft: R = 0.510Ω

Page 9: Sample Problem

• Lamp Power Calculation:

  • Voltage (V) = 120V

  • Current (A) = 0.5A

  • Power (P) = EI = 120V x 0.5A = 60W.

Page 10: Electric Circuit

Definition

• An interconnected path for electrical flow, also known as an electric network.

Components

• Branches: Comprised of one or more elements in series.

• Nodes: Points where branches meet.

• Loops: Form closed paths.

Page 11: Circuit Configurations

Types of Circuits

• Series: Components linked end-to-end.

• Parallel: Components share the same voltage source.

Key Points

• In parallel circuits, voltage remains equal while current adds up.

Page 12: Kirchoff’s Laws

Current Law

• The total current entering a node equals the current leaving.

Voltage Law

• The sum of voltage rises and drops in a closed loop equals zero.

Page 13: Electromagnetism

• Induction: Voltage production when a conductor moves through a magnetic field or vice versa, causing current flow.

Page 14: DC and AC

Types of Current

• Direct Current (DC): Flows in one direction.

• Alternating Current (AC): Flows alternately in two directions.

Frequency

• Measured in hertz (Hz), representing cycles per second.

Page 15: Ideal Transformer

Function

• Transfers AC and voltage between circuits via induction.

Principle

• For an ideal transformer, input power equals output power; VpIp = VsIs.

Page 16: Sample Problem

Transformer Calculation

• Primary voltage (Vp) = 7200V; turns ratio = 30:1.

• Building voltage: Vs = 7200V * (1/30) = 240V.

• Current drawn by the building: Is = 225,000W / 240V = 937.5A.

Page 17: Impedance

Components

• Inductors: Coils creating electromagnetic fields; phase lag in AC circuits.

• Capacitors: Store electrostatic energy; phase lead in AC circuits.

Impedance (Z)

• Resistance measure in AC circuits, incorporates resistance, inductance, and capacitance effects.

Page 18: Power Factor

Definitions

• Real Power (W): Effective work accomplished (heat, light).

• Reactive Power (VAR): Power for electromagnetic fields.

• Apparent Power (VA): Total power encompassing both real and reactive power.

Power Factor (pf)

• Ratio of real power to apparent power, indicating efficiency.

Page 19: Sample Problem

Power Factor Calculation

• Real Power = 3,000W; Apparent Power = 3,600VA.

• pf = 3000 / 3600 = 0.833 or 83.3%.

• Phase angle Φ = cos⁻¹(0.833) = 33.6º.

Page 20: Sample Problem

Real Power Calculation

• Voltage = 240V; Current = 10A; pf = 0.833.

• PA = EI * pf = 240 V * 10 A * 0.833 = 1,999W.

Page 21: Power Factor Correction

Importance

• Higher power factor reduces load currents, saving costs on equipment.

• Correcting low power factors avoids penalties from power companies.

Page 22: Electrical Power System

• Components:

  • Electrical consumers (commercial, industrial, domestic).

  • Electricity distribution via substations, transformers, and main transmission lines.

Page 23: Power Formulas Overview

DC and AC Power Formulas

• Real Power (W), Apparent Power (VA), Current (A) calculations provided.

Page 24: Energy Costs Calculation

Example

• Lamp Consumption: 60W for 24 hours/day, 30 days.

  • Total Energy = 43.2kWh; Cost = $5.06 at $0.1172/kWh.

Page 25: Large Residence Energy Charge

Cost Breakdown

• Total charge calculation based on energy consumption and tiered pricing structure provided.

Page 26: Demand Charges

Pricing Structure

• Detailed rates for service charge, energy charges, and scenario calculations.

Page 27: Demand Management Strategies

• Load Shedding: Shutting off non-essential loads.

• Load Shifting: Moving loads to off-peak hours.

• Peak Shaving: Using storage and alternative energy to reduce peak demand.

• Time-of-Use Rates: Incentives for reducing consumption during peak demand.