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1. Principles of Electrical Engineering
1.1 Fundamentals of Electronics
The purpose of this section is to briefly touch upon fundamentals of electronics that will
be discussed in the report.
1.1.1
Current
Current consists of the flow of very large numbers of charged particles through a conductor. These charged particles are electrons and protons which are commonly referred
to as elementary charges. Electric current is defined as the time rate of change of charge
passing through a predetermined area4. Electric current is measured in amperes or amps
(A).
1.1.2
Voltage
A voltage, or potential difference, between two points in a circuit indicates the energy
required to move charge from one point to another4. The voltage is a measure of the
driving force for the flow of current through a circuit or conductor. This potential
difference is measured in a unit called Volt (V).
1.1.3
Resistance
When electric current flows through a conductor it encounters a certain amount of
resistance. Resistance is the opposition to current that is provided by the conductor5.
This resistance is measures in a unit called ohms (Ω).
1.1.4
Direct Current
Direct current (DC) is the flow of charge in one direction through a conductor. As shown
in Figure 1, the current flows in one direction through the circuit and is constant in
magnitude and direction.
1
Figure 1 – Direct Current5
1.1.5
Alternating Current
Alternating current (AC) is bi-directional, meaning that the flow of charge changes
direction periodically5. As shown in Figure 2, the magnitude and direction of the current
are not constant. From period t0 to t1 the current is positive and the flow in the circuit is
clockwise. From period t1 to t2 the current is negative and the flow in the circuit is
counter-clockwise.
Figure 2 – Alternating Current5
1.1.5.1 Three Phase AC Power
Three phase power is produced when three sinusoidal voltages that are shown in Error!
Reference source not found. are generated 120o out of phase with one another. Advantages of three phase over single phase power include increased efficiency and
constant supply of power.
2
1.1.5.2 Three Phase Power Delta and WYE Connections
Three phase delta and WYE connections are two different arrangements where AC
sources are connected. Figure 3 shows a delta configuration on the left and a WYE
configuration on the right.
Figure 3 – Delta and WYE Configurations4
1.2 Fundamentals of Circuitry
1.2.1
Energy Storage in Circuits
Capacitance and Inductance are two methods for energy storage in a circuit. Both these
methods store energy in an electromagnetic field. Two electrical components that can
induce capacitance and inductance in a circuit are called capacitors and inductors,
respectively.
1.2.1.1 Capacitors
The most basic type of capacitor is constructed with two parallel plates and is separated
by an insulating material, as shown in Figure 4. In a DC circuit a capacitor acts as an
open in the circuit.
3
Figure 4 – Capacitor Construction5
1.2.2
Inductors
1.2.3
Grounding
1.2.4
Shorting
1.3 Cabling
1.3.1
Wire Shielding
1.3.2
Isolated Wires
1.4 Signals
1.4.1
Signal Noise
1.5 Schematic Symbols
Wires
Connected
Ground
Symbols
Coaxial
Cable or
Shielded
Line
XXXXXXX6
4
Shielded
Conductor
Shielded MultiConductor
Cable
5