Jadeer Learning Manual - Electrical Basics

Jadeer Learning Manual - Electrical Area 2

• This manual covers plant electrical installation - level 1
• Date of issue: 6 November 2024
• Next review date: 1 October 2027
• Document reference: JAD-LC-A2-YP-EMT-LM
• Module: 2024
• Revision: 2024.01

Basics of Electricity

• Elements of an Atom: All matter is composed of molecules, which are made up of a combination of atoms. Atoms have a nucleus with electrons orbiting around it. The nucleus is composed of protons and neutrons. Most atoms have an equal number of electrons and protons. Electrons have a negative charge (-). Protons have a positive charge (+). Neutrons are neutral.
• Free Electrons: Electrons in the outer band can become free of their orbit by external forces (magnetic fields, friction, or chemical action). These "free electrons" move from one atom to the next, creating electron flow which is the basis of electricity.
• Conductors: Materials that allow many free electrons to move freely are called conductors. Copper, gold, silver, and aluminum are examples of good conductors. Copper is widely used due to its relative low cost.
• Insulators: Materials that allow few free electrons are called insulators. Plastic, rubber, glass, mica, and ceramic are examples of good insulators. Insulators are used to prevent electrons from flowing outside the conductor pathways.
• Semiconductors: Materials exhibiting characteristics of both conductors and insulators, such as silicon. Semiconductors are used to create transistors, diodes, and other solid state electronic devices.

Basic of Electricity Learning Content

• Table of Contents (page 5)
• Learning Objectives (page 6)
• Basic Introduction of Electricity (page 8)
• DC and Magnetism (page 8)
• Understanding of AC Circuits (page 8)
• Series and Parallel Circuits (page 8)
• Understanding of Electrical Formulas (page 8)
• Understanding of Power Triangle (page 8)

Objectives

• Basic understanding of DC and Magnetism (page 5)
• Basic understanding of AC Circuits and Series/Parallel Circuits (page 5)
• Understanding of Power Triangle (page 5)

Common Electrical Hazards

• Electrical injuries are a serious concern, with 4,309 employees on average taking time off work for injuries between 1992 and 2001
• Electricity can cause both immediate and secondary effects including: tingling sensations, muscle contractions, respiratory paralysis, heart clamps, tissue and organ burns.
• Exposure even at low levels (3 milliamperes) can injure.

Preventing Workplace Hazards

• Electrocution is a leading cause of workplace fatalities
• Younger workers have a higher risk of death from electrical shock.
• Many workplace electrocutions involve contact with power lines while handling equipment.

Basic Introduction of Electricity

• Atoms are the basic building blocks of all matter
• Atoms have nuclei with electrons orbiting around them
• Atoms have equal numbers of protons and electrons.
• Electrons carry a negative charge ( - ) and protons carry a positive charge (+)
• Electrons being attracted to protons, are bound in their orbit

Attraction and Repulsion of Electric Charges

• Opposite charges attract, and similar charges repel
• Charged bodies create an invisible electric field
• Coulomb's Law: The force of attraction or repulsion depends on the strength of charges and the distance between them

Current

• Electricity is the flow of electrons in a conductor
• Current is measured in amperes (amps), denoted by the symbol "A".
• Direct current (DC) flows in one direction consistently.
• Alternating current (AC) periodically changes direction.

Voltage

• Voltage, electromotive force (emf), or potential difference is the force required to make electricity flow through a conductor
• It is measured in volts, represented by the letter “V”.
• A difference in potential exists between the terminals of a voltage source.
• For DC, voltage polarity remains unchanged, while AC polarity alternates.

Resistance

• Resistance in an electrical circuit opposes the flow of current
• Resistance depends on material composition, length, cross-section and temperature
• The unit of measurement for resistance is ohms (Ω).

Ohms Law Triangle

• Ohm's law relates current (I), voltage (E), and resistance (R)
• The illustration shows how to calculate any unknown value using the appropriate formula: E = I xR; I = E / R; R = E / I

Basics of Electricity (DC and Magnetism)

• Principles of magnetism are important to electricity, and vice-versa
• All magnets have two poles: north and south.
• Invisible magnetic flux lines emanate from the north pole and enter the south pole.
• Magnetic fields can be shown visually using iron filings.
• Like poles repel, and unlike poles attract.

Electromagnetism

• Electric currents generate a magnetic field.
• A relationship exists between the direction of current flow and the direction of the magnetic field (left-hand rule).

Electromagnets

• A coil of wire carrying current acts like a magnet.
• Increasing the number of turns in a coil, current, or having the coil around a conductive material as a core increases the strength of the magnetic field generated.
• Used in many electrical devices as motors, circuit breakers, and relays

Understanding of AC Circuits AC Current

• The supply of current for electrical devices may come from a direct current (DC) source or an alternating current (AC) source.
• In a direct current (DC) circuit, electrons flow continuously in one direction from the power source through a conductor to a load and back to the power source.
• In an alternating current (AC) circuit, the flow direction reverses many times a second reversing (changing) polarity.
• AC is represented graphically as a sine wave.
• The vertical axis represents the magnitude of current or voltage.

Basic AC Generator

• Includes a magnetic field, an armature (consisting of conductive wires in loops), slip rings, and brushes.
• A voltage is induced in the conductor as the armature rotates through a magnetic field.
• The current flows from the armature to the load via the slip rings and the carbon brushes.
• This process continues as long as the generator is in operation.

Frequency

• Frequency is the number of cycles per second of voltage induced in the armature.
• The unit of frequency is Hertz (Hz), with a cycle per second being equal to 1 Hz.
• Common power line frequencies in many countries are 50 and 60 Hz.

Four-pole AC Generator

• A two-pole AC generator completes one cycle for each revolution.
• A four-pole AC generator completes two cycles per revolution
• Increased poles increase frequency

Amplitude

• Amplitude in AC current or voltage is variation in value.
• Three ways to express or measure amplitude: peak value, peak-to-peak value, and effective value.
• Peak is the maximum value on one-half cycle
• Peak-to-peak is from +peak to -peak
• The effective value is also known as the RMS value, approximately 70.7% of the peak value.

Calculating Impedance

• Impedance is the total opposition to current flow in an AC circuit
• It's represented as a vector with both magnitude and direction
• Impedance vector angle corresponds to phase relationship between voltage and current.

Series RLC Circuits

• RLC circuits have resistance, inductance, and capacitance in series
• Calculated using Ohm's Law for current
• Inductance and capacitance add to total opposition, called reactance, in opposing current directions.

Parallel RLC Circuits

• Parallel circuits have resistance, inductance, and capacitance in parallel, and increase circuit capacitance.
• Total capacitance is the sum of each capacitor value
• The total resistance value is inversely proportional to the individual resistance values in the parallel circuit

Capacitors

• Capacitance is a measure of a circuit's ability to store an electrical charge
• Capacitance is a function of the plate area, distance between plates, and type/material of the dielectric between the plates
• Farad (F) is the standard unit of measurement for capacitance.
• Microfarads (µF) and picofarads (pF) are frequently used smaller units of measurement for capacitance.

Capacitance in Series/Parallel

• Connecting capacitors in series decreases the total capacitance
• Connecting capacitors in parallel increases the total capacitance

Inductive Reactance

• Inductive reactance is the opposition to changing currents in AC circuits
• Inductive reactance varies with both frequency (f) and inductance (L) values.

Current and Voltage Phases

• Resistance circuits have current/voltage in phase.
• Inductive circuits have current lagging the voltage by 90°
• Capacitive circuits have current leading the voltage by 90°
• Circuits with resistance and reactance (inductive or capacitive) fall somewhere in the in-between.

Transformers

• Transformers transfer electrical energy from one circuit to another via mutual induction.
• A single-phase transformer has a primary and secondary coil.
• Transformers are rated in kilovolt-amps (kVA) which determines the current and voltage that can be delivered to the load (motor, appliances etc.) without overheating
• Transformers can be used to step up or down voltage.

Residential Transformer Applications

• A typical residential system uses 120V to outlets and 240V for high loads (heat, air, cooking)

Three-Phase Power

• A three-phase system provides improved voltage and current outputs over single-phase systems.
• Three-phase systems are common in industrial settings.

Power in AC Circuits

• In resistive circuits, power is dissipated as heat.
• True power is the actual power consumed by the circuit and is the current squared times resistance.
• Reactive power is related to the inductance/capacitance causing power to return to the source.
• Apparent power is total power delivered, is the sum of true power and reactive power.

Power Factor

• Power factor is a ratio expressing how efficient power is used.
• It is calculated using the cosine of the angle between voltage and current.
• A power factor of 1.0 means all the delivered power is consumed while a value of 0 means no power is consumed, (lost).

Series Circuit Resistance

• Resistances are added together to find the total resistance in a series circuit arrangement

Series Circuit Voltage and Current

• Total circuit current is determined by dividing the source voltage by the total circuit resistance
• Voltage drop across each resistor is the current flow times its circuit resistance; (sum of all resistor voltage drops = source voltage)

Parallel Circuit Resistance

• The total resistance of a series circuit is the reciprocal of the sum of the reciprocals of the individual resistances.

Parallel Circuit Current

• Total current is the sum of individual currents flowing through each component/resistor.
• Current in each parallel component/resistor is equal to the total circuit voltage divided by the individual component/resistor resistance.

Contact 'normal' state and break sequence

• The 'normal' state is when a switch or a relay is not influenced by any outside processes.
• 'normally open' contacts are open when the contact is not activated, while 'normally closed' contacts are closed when the contact is not activated

Generic Symbology

• Normally-open contacts are denoted by two unconnected parallel vertical lines
• Normally-closed contacts are denoted by two parallel vertical lines connected by a diagonal

Electro-mechanical Switches

• Introduction (page 84)
• Contactor (page 84)
• Construction (page 85)
• Operating Principle (page 87)
• Rating (page 88)
• Basic Design and Operation (page 95)
• Types of Relay (page 97)
• Applications (page 108)
• Relay Application Considerations (page 109)

Time Delay Relays

• Introduction (page 115)
• Normally-Open, Timed-Closed (page 116)
• Normally-Open, Timed-Open (page 117)
• Normally-Closed, Timed-Open (page 118)
• Normally-Closed, Timed-Closed (page 119)
• Time-Delay and Logic Circuits (page 120)

Digital Logic Functions

• Introduction (page 128)
• Digital Logic Functions (page 128)
• Permissive and Interlock Circuits (page 138)
• Motor Control Circuits (page 142)

This quiz covers the fundamentals of electricity, including the structure of atoms, free electrons, and conductors. It is essential for individuals studying electrical installation at a foundational level. Understanding these concepts is crucial for further exploration in the electrical field.