FOUNDATION OF ELECTROTECH
| Site: | ElectroTech Skills Hub |
| Course: | ElectroTech Skills Hub |
| Book: | FOUNDATION OF ELECTROTECH |
| Printed by: | |
| Date: | Tuesday, 16 September 2025, 1:43 AM |
1. Electrical Fundamentals
1.1 Basic Electrical Quantities
1.1.1 Voltage, Current, and Resistance:
Voltage is the potential difference between two points in an electric field, measured in volts (V). Current is the flow of electric charge through a conductor, measured in amperes (A). Resistance is the opposition to the flow of current, measured in ohms (Ω). Ohm’s Law relates these quantities with the formula V = IR.
1.1.2 Power and Energy:
Power is the rate at which electrical energy is transferred by a circuit and is measured in watts (W). It is calculated using the formulas P = VI or P = I²R. Energy consumption, often billed in kilowatt-hours (kWh), is the total power used over time and is crucial for managing electricity usage in homes and industries.
1.2 Circuit Elements and Tools
1.2.1 Passive Components:
Resistors limit current, capacitors store and release energy, and inductors resist changes in current. These components are essential in shaping the behavior of electrical circuits. They are used in filtering, timing, and energy storage applications. Color codes on resistors indicate their resistance value.
1.2.2 Electrical Tools and Safety:
Common tools include pliers, wire strippers, multimeters, and screwdrivers. Safety gear such as gloves, safety boots, and insulated tools protect against electric shocks and injuries. Safe working practices include verifying circuits are de-energized and using lock-out/tag-out procedures.
2. Electrical Installation and Wiring
2.1 Domestic Installations
2.1.1 Lighting and Socket Circuits:
Lighting circuits typically use single-phase wiring with switches and loop-in systems. Socket outlets are connected in ring or radial configurations. Proper circuit design ensures load balancing and minimizes voltage drop.
2.1.2 Protection and Earthing:
Protection devices such as MCBs, fuses, and RCDs prevent overcurrent and shock hazards. Earthing provides a safe path for fault currents, reducing the risk of electrocution. Bonding ensures all metal parts are at the same potential, enhancing safety.
2.2 Commercial and Industrial Installations
2.2.1 Three-phase Systems:
Used in industries for heavy loads, three-phase power offers balanced loads and improved efficiency. Configurations like star (Y) and delta (Δ) determine voltage and current levels across circuits. Load balancing across phases prevents overloading and system failure.
2.2.2 Cable Management:
Proper routing of cables using conduits, trunking, and trays ensures safety and maintenance ease. Cable sizing depends on load current, insulation type, and installation conditions. Overloaded or improperly routed cables can overheat and cause fires.
3. Electrical Machines and Control
3.1 Rotating Machines
3.1.1 AC and DC Motors:
AC motors include induction and synchronous types, commonly used in appliances and industries. DC motors are used in variable speed applications. Understanding torque, speed, and efficiency helps in selecting the right motor for a task.
3.1.2 Transformers:
Transformers transfer electrical energy between circuits using electromagnetic induction. They are used for stepping voltage up or down in power distribution. Key parameters include turns ratio, efficiency, and types of losses (core and copper losses).
3.2 Control Systems
3.2.1 Manual Starters and Contactors:
Manual starters control motor operations, protecting them during start and stop. Contactors are electrically controlled switches used in automation and remote control. Star-delta starters reduce inrush current during motor start-up.
3.2.2 Programmable Logic Controllers (PLCs):
PLCs automate industrial processes using ladder logic programming. They monitor inputs and control outputs such as motors, valves, and alarms. PLCs improve efficiency, reduce errors, and enable remote system control.