Electrical Fundamentals (RACM-150)

Electrical Fundamentals (RACM-150)

• This course covers the fundamentals of electricity, including basic concepts, electrical circuits, electronic controls, wiring diagrams, voltage and current measurement, and calculations.

Learning Outcomes

• Demonstrate knowledge of fundamental electrical concepts.
• Demonstrate understanding of electrical circuits and loads.
• Explain the operation of conductors, relays, switches, contactors, overloads, and transformers.
• Describe electronic controls and their operation.
• Interpret electrical wiring diagrams.
• Apply procedures to measure voltage, resistance, current, and power, and calculate their relationships.

Conductors

• Good conductors have few electrons in their outer electron shell.
• Good electrical conductors are generally good heat conductors.
• Conductors allow current to flow through a circuit.
• Conductors have low resistance to electron flow.
• Examples of good conductors include copper and aluminum.

Conductor Ampacity

• Conductors resist current flow.
• Resistance lowers as the conductor size increases.
• Conductors are sized according to their ampacity.
• Ampacity rating defines the maximum current a conductor can carry safely.
• The ampacity must be properly sized by a certified electrician.
• Ampacity ratings are often based on temperature (e.g., 60°C).

Ampacity Chart (Copper)

• Provides the ampacity ratings for different copper wire sizes (AWG).
• Table lists ampacity values for different wire gauges based on temperature.
• Small conductor ampacities are specified (e.g., 15 amps for No. 14 copper, 20 amps for No. 12, 30 amps for No. 10).

Insulators

• Insulators are the opposite of conductors.
• Insulators have many electrons in their outer shell.
• Electrons in insulators are difficult to move from one atom to another.
• Non-metallic materials are good insulators (e.g., glass, air, rubber, plastic).

Magnetism and Electricity

• Magnets have north and south poles.
• Opposite poles attract, like poles repel.
• A magnetic field is created around a conductor when current flows.
• Increasing the number of turns in a coil strengthens the magnetism.

Current (A)

• Current is the flow of electrons.
• Measured in amperes (amps).
• Current describes the amount of electrical work done.
• Direct current (DC) and alternating current (AC) are two types of current.
• Current flows from higher to lower electrical potential difference.
• Current follows the path of least resistance.

Direct Current (DC)

• Flows in one direction.
• Electrons flow from negative to positive.
• DC power supplies have constant voltage.
• DC power is typically generated by chemical reactions (e.g., batteries).
• Rectifiers convert AC to DC current.
• Batteries are a source of DC current.

Alternating Current (AC)

• Continuously and rapidly reverses direction.
• Common in public electrical use.
• Easier to transmit long distances because the voltage can be readily changed.
• Single-phase and three-phase are common implementations.

AC vs DC

• AC current changes direction, from positive to negative in a sinusoidal pattern.
• Frequency is the amount of cycles per second, measured in Hertz.
• 60Hz means 60 cycles per second in power flow.

Voltage (EMF)

• Voltage, or electromotive force, describes the speed at which electrons are moving.
• Voltage is a measure of potential difference.
• A closed circuit with equal potential difference means 0V.
• One volt is needed to flow 1amp of current through 1ohm of resistance.

Resistance

• Resistance is the opposition to current flow.
• Resistance increases when current flow decreases.
• Resistance is measured in Ohms.
• One ohm is present when 1 volt causes 1 amp of current to flow.

Power

• Power (watts) is the rate at which electrical energy is used or generated.
• Power is measured in watts (W) or kilowatts (kW).
• Kilowatts (kW) per hour (kWh) measures energy consumption.
• Power = voltage × amperage.

Ohm's Law (V = I × R)

• Ohm's Law describes the relationship between voltage, current, and resistance.
• Used to calculate an unknown electrical value from other known values in a circuit. The formula provides tools to find voltage, current, or resistance by covering up that value.

Ohm's Law Applications

• Practical examples of calculating resistance, voltage, and current in electrical circuits.

Watts Law (P = V × I)

• The relationship between power (watts), voltage, and current.
• The wattage of a 120V circuit with a 6 amp current draw is 720 watts.

Electrical Measurements

• Measurements involve Watts (power consumption), kilowatts (large power consumption), Amperage (current), Voltage (force), and Ohms (resistance).
• Units include watts (W), kilowatts (kW), amperes (A), volts (V), and ohms (Ω).

Magnetism

• A magnetic field exists around a current-carrying conductor.
• Increasing the turns of a wire creates a stronger magnetic field.
• A solenoid is a tightly wound coil of wire that acts as a strong electromagnet

Inductance

• The opposition to change in the flow of alternating current.
• Back EMF (electromotive force) in electric motors happens due to changing magnetic fields.

Inductive/Capacitive Reactance

• Resistance to current flow in AC circuits.
• Inductive reactance is the opposition to changes in current direction.
• Capacitive reactance is opposition to changes in voltage in an AC circuit.

How it Affects the Circuit

• Inductive reactance causes voltage to lead current.
• Capacitive reactance causes current to lead voltage in AC circuits.
• Impedance is total opposition in AC circuits.

Transformers

• Device converting AC voltage from one level to another (step-up/down).
• Uses electromagnetic induction.
• Step-up transformers increase voltage, and step-down transformers decrease voltage.
• Transformers are rated in volt-amps (VA).

Transformer Application

• Step down transformers reduce higher line voltages for controllers (24V).
• They lower or raise voltage for different components to work.
• Used to increase voltage for sparks, motors, or special applications (ex: 120V to 10,000V).
• Step-down transformers are often used in control systems to reduce high line voltage to a lower voltage.

Capacitance

• The ability of a capacitor to store electrical energy.
• Measured in microfarads (µF).
• Allows for the storing and releasing of electrical charge within a circuit.
• Exact values or close approximations can be utilized when replacing components.

Short Circuits

• Unsanctioned path to ground.
• Occurs through a low-resistance pathway.
• Creates a surge of current, potentially blowing fuses or tripping breakers.
• Short circuits can occur to ground or between lines and often cause a surge of current that can trigger protective devices.

Series Circuits

• One path for current flow.
• Components are connected in a line.
• If one component fails, the whole circuit shuts down.

Parallel Circuits

• Current flows through multiple branches.
• Components are connected across common points.
• Failure in one component does not affect other components.

Series-Parallel Circuits

• Circuits combining series and parallel configurations.
• Loads are connected in parallel, and some switching elements are in series with the load.

Resistance and Current Calculation

• Series circuit resistance calculated as the sum of individual resistances.
• Parallel circuit resistance calculated by the inverse sum of reciprocals of individual resistances.
• Current and total current values differ depending on whether the circuit is in series or parallel.
• Current and total current calculations differ between series and parallel circuits.

Reading Schematics/Diagrams

• Understanding and interpreting schematic diagrams for AC systems.

Type of Relays and Contactors

• Information on common relays used in HVAC/R (heating, ventilation, and air conditioning/refrigeration) systems.
• Type of relays and contactors typically used in HVAC/R systems.

This quiz covers the essential concepts of electrical fundamentals as outlined in the RACM-150 course. You will explore topics such as electrical circuits, electronic controls, and wiring diagrams, as well as measurement techniques for voltage and current. Test your understanding of these fundamental concepts and their applications in electrical engineering.