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Variable Frequency Drives
Robert J. Scoff, P.E.
Overview
I wrote this courses
with the intention of showing how the various parts of a Variable Frequency
Drive (VFD) work and how they are integrated to make an operating system. It
starts with a review of AC and DC theory that is applicable to the way that an
Inverter (another name given to VFD’s) works. An explanation is given of how
the various solid state electronic components work. This course then shows how
a three phase constant frequency (60 hertz in the USA) input voltage is turned
into a DC voltage, and then the DC voltage is turned into a three phase,
variable frequency, variable voltage output. There are many pictures that give
a real feeling of how these devices really operate. A historical overview is
also presented to show the development of the technology of VFD’s.
This course was designed for
electrical engineers as well as engineers of other disciplines. Electrical
engineers will have a deeper understanding of how basic principles and basic
devices are put together to make this versatile machine work. This will help
them as they apply it to various projects. Engineers in other disciplines will
also find it useful to have an understanding of how variable frequency drives
work, as they work with mechanical, chemical, and building systems. The more
that we, as engineers, understand how things in other disciplines work, the
better that we can do our specific jobs.
There is very little math
involved in the doing of this course. It always helps to understand basic
algebra. This course is built on understanding the parts of an inverter, and
how they work together to make an operating system.
The student must take a
multiple choice quiz consisting of twenty 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 Variable Frequency Drives, 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:
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Some history of VFD’s.
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Definitions of applicable
electrical terms.
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Learn the operation of the
solid state devices that are used in inverters.
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Learn how the various parts
of an Inverter work together to generate a variable frequency, variable
voltage signal from a 60 Hertz input voltage.
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Learn how the controls work
to make an inverter work.
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Learn how to handle a few
of the problems encountered when VFD’s are applied in the work world.
Course
Click on the following PDF attachment and review the document
"Variable Frequency Drives" prior to taking
a quiz for credit.
Variable Frequency Drives (307 KB)
Having Trouble Downloading the PDF File?
Right click on the link. Select "Save Target As..."
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To obtain PDH credits for this course, you will need to take a quiz for
credit. Click on the link below.
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