Electrical Fundamentals: Level 1

Electrical Fundamentals: Level 1

• This content serves as an introduction to electrical fundamentals.
• It covers concepts, circuits, components, diagrams, and measurement procedures.

Learning Outcomes

• A student should be able to demonstrate knowledge of electronics regarding electricity.
• This includes circuits, loads, conductors, relays, switches, contactors, overloads, transformers and their operations.
• A student should be able to demonstrate knowledge of electronic controls and wiring diagrams.
• A student should be able to demonstrate the ability to measure voltage, resistance, current and power, and calculate their interrelationships.

Conductors

• Good conductors have few electrons in their outer shells.
• Good conductors of electricity are generally good conductors of heat.
• Conductors carry current through a circuit and have low resistance to electron flow.
• Metallic materials such as copper and aluminum are good conductors.

Conductor Ampacity

• As the conductor size increases, resistance decreases.
• Conductors sized by their ampacity rating.
• Electricians typically size conductors.
• Having a basic understanding of conductors can be helpful when purchasing a whip.

Insulators

• Insulators are the opposite of conductors.
• Insulators have several electrons in their outer shell.
• Their electrons are difficult to free, impeding electron movement between atoms.
• Non-metallic materials like glass, air, rubber, and plastic serve as good insulators.

Magnetism and Electricity

• Magnets possess two poles: north and south.
• Opposite poles attract, creating lines of force.
• When a conductor is placed within these lines, electrons in its atoms are freed.
• This results in a surplus of electrons on one side of the conductor, creating a potential difference known as voltage.

Current

• Current refers to the number of electrons flowing, measured in amperes (amps).
• Amps quantify the amount of work being done.
• Two types: direct current (DC) and alternating current (AC).
• Current follows the path of least resistance until charge is equalized.

Direct Current (DC)

• Direct current travels in one direction and electrons flow from negative to positive.
• DC power supplies a constant voltage, typically generated by chemical reactions.
• Alternating current can be converted to DC using a rectifier.
• Batteries provide a good example of a DC power source.

Alternating Current (AC)

• Alternating current continually and rapidly reverses its flow.
• Most electricity for public use is generated as AC because it is practical for long-distance transmission, and voltage can be readily changed.
• Utilizes both single-phase and three-phase configurations.
• Canada uses a frequency of 60 Hz, meaning 60 cycles.

Voltage (EMF)

• Electromotive force/voltage measures the speed of electron movement.
• Voltage measures potential difference.
• Measuring voltage on the same line of power with a closed switch yields 0V due to no charge difference.
• One volt equates to the force needed to push one amp of current through one ohm of resistance.

Resistance

• Resistance in a circuit is the opposition to current flow.
• Increased resistance decreases current flow via inductive loads.
• Ohms are the most common unit of measurement for resistance.
• One ohm exists when one volt causes a current of one amp to flow.

Power

• Power refers to the rate of electrical energy transfer or storage.
• Power is measured in watts (W) or kilowatts (kW).
• Power companies measure power usage in kilowatt-hours (kW/h).
• This is the quantity of kilowatts used per hour.
• Power(w) is calculated by voltage multiplied by amperage.

Ohm's Law

• Describes the relationship between voltage, current, and resistance.
• Electromotive force (V) = amperage (I) x resistance (R).
• A user can calculate one value if the other is known.

Ohm's Law Applications

• To find the resistance of a 120V circuit drawing 3 amps requires dividing voltage by amperage (R = E/I), resulting in 40 ohms.
• Determining the voltage of a circuit drawing 2A at 60 ohms is found by multiplying current by resistance (V = I x R), equaling 120V.
• Calculating the current draw of a 120V circuit with 20 ohms of resistance involves dividing voltage by resistance (I = E/R), yielding 6A.

Watt's Law

• Watt's Law describes the relationship between voltage, amperage, and power.
• It is expressed as watts (p) = volts (v) x amps (I).
• The wattage of a 120V circuit drawing 6 amps is 720 watts (P=VxI=120x6).

Basic Electrical Measurements

• Watts (W) measure of power consumption.
• Kilowatts = W/1000.
• Amperage (A) represents current.
• Voltage (V) represents force.
• Ohms (Ω) measure resistance.

Magnetism

• A magnetic field is generated around a conductor whenever current flows.
• Magnetism increases when the wire is formed into a loop.
• Magnetism is further enhanced if the wire is wound into a coil.
• A coil of wire carrying current is a solenoid.
• The solenoid attracts an iron bar into the coil; the iron bar is the plunger.

Inductance

• Inductance is a fluctuation of magnetic strengths in AC circuits.
• It induces a voltage that counteracts the original voltage.
• When a motor spins, back electromotive force (EMF) is created, opposing current flow due to the motor's magnets and tightly wound coil.
• Motors, solenoids, and coils are inductive loads.

Inductance and Capacitance Reactance

• Reactance is the resistance faced by alternating current when changing direction.
• Resistance in a DC circuit is the only factor affecting current flow.
• In AC circuits, resistance, inductive reactance, and capacitance reactance all influence current flow.
• Capacitance reactance occurs in circuits with capacitors resist voltage changes.

Types of Resistances in a Circuit

• Inductive reactance opposes changes in AC current flow, causing voltage to lead current.
• Capacitive reactance opposes changes in voltage in an AC circuit, causing current to lead voltage.
• Impedance is the total resistance of a circuit.
• This is calculated inductive reactance + capacitive reactance + resistance.

Transformers

• Transformers are electrical devices inducing a secondary voltage through electromagnetic induction.
• Step-up transformers have more windings on the secondary side, increasing voltage.
• Step-down transformers have more windings on the primary side, decreasing voltage.

Transformer Ratings and Applications

• Transformers are rated in volt-amps (VA).
• They are typically used to step down line power to 24V control power.
• They can step down higher line voltage to lower line voltage such as 575V to 120V.
• This is used to operate different components like an inducer motor on an RTU.
• Step-up transformers are used to raise voltage to supply a motor or create a spark for gas ignition, for example, 120V to 10,000V.

Capacitance

• A capacitor stores electrical energy in an electric circuit for later use.
• Capacitance refers to the amount of charge the capacitor has stored.
• Capacitors are rated in microfarads (uF).
• If replacing a capacitor, a user can increase it's rating by up to 10% of the original rating.

Short Circuits

• A short circuit provides an unintended path to ground or from line to line.
• Electricity will take the path of least resistance.
• Shorts can occur to the ground, or line-to-line.
• Short circuits are characterized by low resistance.
• Low resistance leads to an unwanted current flow and cause fuses to blow.

Series Circuits

• Series circuits allow only one path for current flow.
• Switches and controls are typically wired in series.
• In series circuits everything is inline with the bulb.

Parallel Circuits

• Electrical loads are arranged in parallel circuits.
• Parallel circuits ensure each load is connected to both supply voltage lines.
• Parallel circuits allow the current to travel in more than one path.

Series-Parallel Circuits

• These are combination circuits.

Resistance and Current Calculations

• In the series circuits, the total resistance is the sum of all resistances added together (Rt=R1+R2+R3…and so on).
• In series circuits, the current draw is the same throughout because there is only one path for the electrons to flow ( C(t) = C1=C2=C3...and so on).
• Calculating total resistance in parallel circuits involving two resists is R1 x R2 / R1 + R2.
• The current is the sum of all loads such as Ct=C1+C2+C3..and so on.

Solving Example Parallel Circuit Problems

• A 240V parallel circuit with two resistances has a total resistance of 7.06 ohms (R1 = 10 ohms, R2 = 24 ohms).
• In a 240V parallel circuit containing resistances of 3 ohms, 6 ohms, and 12 ohms, the total current draw totals 140 amps.

Calculating Voltage Drop

• Voltage drop vary across each resistance.
• The sum of the voltage drop across the whole circuit will be equal to the voltage applied.
• For instance, in a series heating circuit with a 120V incoming voltage source and four heaters (4 ohms, 10 ohms, 14 ohms, and 12 ohms), the total resistance equates to 40 ohms.
• Using I = E/R, the calculated total current is 3 amps. Applying E = I x R, the voltage drops across each resistor (heater) result in a total of 120 volts, matching the source voltage.