|
A Unique and Understandable Way to Look at
Three Phase Circuits
Robert J. Scoff, P.E.
Overview
I wrote this course with
the intention of removing the magic and mystique that surrounds the idea of
three phase circuits. With that in mind, this course starts by reviewing single
phase alternating current circuits including resistive, capacitive, and
inductive circuits. This is a quick review emphasizing voltage, current, and
power relationships in these three common circuit elements. Waveforms and their
relationship to vectors is shown. Then most three phase circuits are shown to
be nothing more than a number of single phase circuits. Then using some simple
circuit techniques including Kirchoff’s Voltage and Current Laws and
Superposition, voltage, current, and power relationships in three phase circuits
are easily seen. Also, a simple explanation of RMS voltages and currents, and
the reason that RMS is used, is given.
This course was designed
for both engineers in disciplines other than electrical, and electrical
engineers who desire to deepen their understanding of three phase circuits.
This course is more theoretical, but is easily adapted to the practical world
of industrial and commercial electrical systems.
The material in this
course is presented with numerous diagrams, waveforms, and vectors to help
students understand how electrical power works. The material assumes some skill
in basic mathematics, trigonometry, vector analysis, and the ability to convert
between polar and rectangular co-ordinates. A calculator that does polar to
rectangular and rectangular to polar conversions is very helpful in working
through this material. Four templates to help apply this understanding to the
real world are given for the students to use to help them in their work with
three phase power.
The student must take a
multiple choice quiz consisting of twenty (20) questions at the end of the
course to obtain PDH credits. It is my intention that the material presented in
this course help the students be better versed in three phase circuits, and
therefore be more comfortable when working with engineers, technicians, and
craftsmen in the field.
Specific Knowledge or Skill Attained
This course teaches the following specific knowledge and
skills:
-
Definitions of specific
electrical terms.
-
Relationship between
voltage, current, and power versus time for alternating current circuits.
-
How to determine
currents in three phase circuits when voltages and loads are known.
-
How to replace a Delta
three phase source with a Wye three phase source and vice versa.
-
What phase sequence
means and how a phase sequence indicator works.
Course
Click on the following PDF attachment and review the document
"A Unique and Understandable Way to Look at Three Phase Circuits" prior to taking
a quiz for credit.
A Unique and Understandable Way to Look at Three Phase Circuits (647 KB)
Having Trouble Downloading the PDF File?
Right click on the link. Select "Save Target As..."
Then save on your desktop. To view the file, double click the icon on your
desktop and return to this page to take the quiz.
You may need Acrobat Reader to view this document.
Click on the link below to download a free copy of Acrobat Reader.
To obtain PDH credits for this course, you will need to take a quiz for
credit. Click on the link below.
(To take the quiz,
your web browser must be set to accept cookies. See how to
check your cookie settings.)
 
|
