Engineering H191 - Drafting / CAD
AC Electricity
Lab 4
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 1
Engineering H191 - Drafting / CAD
Electric Circuit Components
• Passive:
– Resistors
– Capacitors
– Inductors
• Active:
– Voltage sources
– Current sources
– Amplifiers
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 2
Engineering H191 - Drafting / CAD
Basic Symbols
Battery
Resistor
Autumn Quarter
Generator
Inductor
Gateway Engineering Education Coalition
Capacitor
Lab 4
P. 3
Engineering H191 - Drafting / CAD
AC/DC Comparison
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 4
Engineering H191 - Drafting / CAD
Simple Circuit: Ohm’s Law
• V=i*r
• P=v*i
= i2 * r
V: voltage (Volts)
I: current (Amperes)
R: resistance (Ohms)
P: power (Watts)
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 5
Engineering H191 - Drafting / CAD
Basic Power System
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 6
Engineering H191 - Drafting / CAD
Power System Components
•
•
•
•
•
Generators
Substations: Transformers
Transmission Lines
Distribution Lines
Load
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 7
Engineering H191 - Drafting / CAD
Generation
• Energy conversion:
• Energy balance:
Losses
Mechanical
Electrical
Input
Output
Losses
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 8
Engineering H191 - Drafting / CAD
Substations
• Transformers:
– Fundamentals: faraday’s law
– Real and ideal
– Step-up / step-down
– Turn ratio: n
– Polarity
– Connections: series and parallel
Autumn Quarter
Gateway Engineering Education Coalition
d
en
dt
Lab 4
P. 9
Engineering H191 - Drafting / CAD
Ideal Transformer
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 10
Engineering H191 - Drafting / CAD
Transmission Lines
• High voltage:
– Minimize costs in conductors, towers and
equipment
– Minimize power loss to increase efficiency
– The higher the voltage the smaller the current
and therefore the smaller the losses
P=V*I
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 11
Engineering H191 - Drafting / CAD
Connection of Household Appliances
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 12
Engineering H191 - Drafting / CAD
Power Outlets
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 13
Engineering H191 - Drafting / CAD
Grounding
• Provides safety and potential reference
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 14
Engineering H191 - Drafting / CAD
Hot vs. Cold Resistance
• Conductors (metals) have resistances that are
temperature dependent
• As heat increases, molecular collisions increase,
and resistance to current flow increases as well
• Thus, as resistive elements get hotter, they
become more and more resistive
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 15
Engineering H191 - Drafting / CAD
Measuring Resistance
• Cold resistance can be directly measured
– Disconnect device under test (DUT)
– Attach directly to ohmmeter to take resistance
measurement
• Hot resistance cannot be directly measured
– Measure voltage across DUT
– Measure current in series with DUT
– Ratio of Voltage / Current = Hot Resistance
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 16
Engineering H191 - Drafting / CAD
Questions ?
Autumn Quarter
Gateway Engineering Education Coalition
Lab 4
P. 17