Drives and Motor Controls

Dec. 28, 2012
The Editors of Control Search the World Wide Web to Bring You the Latest on Drives and Motors Controls
Every month, Control's editors take a specific product area, collect all the latest, significant tools we can find, and present them here to make your job easier. If you know of any tools and resources we didn't include, send them to [email protected], and we'll add them to the website.
MOTOR LOAD SLIDE RULEA perennial favorite on our Resources page, this free slide rule shows why measuring power is more effective than measuring just amps. Monitoring power gives you valuable information about mixture viscosity, pump or fan flow, beginning or end of a process and optimum feed rate. This easy-to-use tool visually demonstrates the relationship between power, the power factor, amps and motor power.Load Controls Incorporated888/600-3247

This free, downloadable tutorial covers the basics of AC adjustable-speed drives,  including types of drives, types of variable speed control, adjustable-speed functions, power and torque, advantages and disadvantages, variable- and constant-torque loads and types of AC adjustable-speed drives.  The direct link is at

Danfoss VLT Drives has a number of educational resources available through its website at These include an online diagnostics tool ( for the VLT 2800, VLT 5000, VLT 6000 and VLT 8000 drives, and a collection of lessons on adjustable frequency drives for the industrial market ( and variable frequency drives for HVAC and water and wastewater markets ( A free 150-page downloadable document called "Facts Worth Knowing about Frequency Converters" ( is available that provides an introduction to the work and build-up of a frequency converter and the AC motors connected to it.
Danfoss VLT Drives  

This tutorial deals with direct current permanent magnet motors operated at a constant voltage.  It covers the basic concepts of power, torque and speed and includes sections on torque/speed, power/torque and power/speed curves. Free. The direct link is

Galil has a library of tutorials on motion control subjects, including system design, tuning, motion controllers, motors and drives, software, control of load-sharing systems, Ethernet and motion control and I/O control. The tutorials are free, but registration is required. The direct link is at
Galil Motion Control

The Leonardo Energy organization offers a variety of white papers, blogs, tutorials and courses on electrical subjects. Among its offerings is the Power Quality Tutorial ebook. This is free and downloadable. Sections include coverage of power quality phenomena, problems, solutions and design issues. The direct link is at
Leonardo Energy

This 53-page PDF from the North American Electrical Reliability Corp. (NERC) covers balancing and frequency control concepts, issues and recommendations. Topics discussed include balancing fundamentals, including primary, secondary and tertiary control, time control and inadvertent interchange, frequency correction and intervention, a bibliography and a set of review questions. The direct link is at The PDF is free and downloadable.

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