Web Hunter: Proper electric motor selection and installation can pay dividends

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By Russ Kratowicz

PlantServices.com

Keywords: "electric motors" and "plant energy"

A motor’s lifetime operating cost can exceed its purchase price by an order of magnitude, says Executive Editor Russ Kratowicz. Utilize these Web resources to help you make sure that you're purchasing the right motor.

We’ve heard the bit that claims knowledge is equivalent to power. In our economic system and field of endeavor, one must learn as much as possible about the business, art and science of maintenance lest we see our favorite technical discipline degenerate into nothing more than another battered victim of rampant outsourcing.

It’s always been the philosophy of this publication that you can never get too much education. When things go wrong, if you don’t know the answer or can’t come up with a solution, there’s someone out there who can.

Because electric motors are ubiquitous in the manufacturing arena, they’re sometimes taken for granted. Getting them right the first time, though, is a worthwhile endeavor because, conservatively speaking, a motor’s lifetime operating cost can exceed its purchase price by an order of magnitude. The opportunity exists for you to keep the plant from spending any more than it needs to spend. It takes a little learning. That’s why, this month, we’re digging through the morass we call the Web in search of practical, zero-cost, noncommercial, registration-free resources that can help you become one of the most motor-conversant people in the building. Remember, we search the Web so you don't have to.

Read all about it

It appears that the good folks at SM Service & Technology, a distributor of electric and electronic hardware in Union, N.J., believe that an educated customer is the best customer. I draw this conclusion based on the fact that the company (a) sells motors and (b) posts free educational material about them on its Web site. You will find it at http://smservice.com/litlist.htm. This is the place to visit if you want to know about, for example, reducing power factor cost and optimizing your motor drive system. The total offering includes eight articles, of which you can access six without having to register your identity. This select group comes from the Bonneville Power Administration and each is tagged with the line “Download PDF File.”

From spark to twist

An AC induction motor is nothing more than a device that converts invisible electrical energy into torque, which, in turn, might be persuaded to do some useful work. But don’t think of a motor as a black box whose inner workings are mysterious beyond comprehension. Mankind has been building motors for more years than you can count and the general construction details behind the phenomenon are clearly presented in an article from Control Engineering at www.controleng.com/article/CA6427335.html?rssid=129. Scroll down to the part dated June 21, 2005, and wrap your mind around AC induction motor anatomy, the reasons synchronous and actual speeds differ, and the design and construction differences among several motor varieties.

Northern approach

The U.S. isn’t the only entity on this side of the Atlantic with an interest in motors. Our neighbors to the north have their Office of Energy Efficiency, which is part of Natural Resources Canada in Ottawa and is dedicated to making that country as energy efficient as possible. Part of the obligatory Web site addresses the topic for the month. Pay a visit to http://oee.nrcan.gc.ca and click the following links as pages load: “English,” “Industrial: Facilities and Equipment” and “Technical Information.” If you then select “Energy efficient equipment” and its subcategory, “Electric Motors,” you’re poised to begin a six-part motor article. Heed the warnings about speed and power factor differences between the old and new motor that are listed under purchasing tips. As an aside, select “Tools and Calculators” to take a look at the “Energy Use Calculator,” which tabulates all the energy you bring inside the building envelope or burn up in vehicles.

From the West coast

Southern California Edison, Rosemead, Calif., weighs in with its Web contribution to motor issues at www.sce.com [no hyphens]. The route to this site’s relevant content takes you through “Large Business” in the lower right followed by “Large Business Tips” found under “Tips, Tools & Training.” At that point, scroll down to “Motors” for a set of four articles. Of those, the two best are titled “Improving the Efficiency of Motors” and “Adjustable Speed Drives.” The first shows you how to calculate the dollar value of higher motor efficiency. This knowledge can be useful when you need to cost-justify your next motor purchase. The second offers four practical tips for keeping your drives operating at their best. The remaining articles are too short to be of much value for the purposes of this column.

Discussion group speaks

Research this month uncovered a series of 14 motor-related articles by Howard G. Murphy, P.E. He uses a modified Q&A format that includes a single question followed by answers that appear to have been provided by a discussion group. Topics include calculating motor acceleration, the effect of 50 Hertz on 60 Hertz motors, regenerative braking and motor performance at low speeds. All this is posted on the Web site operated by Rexel, Inc., an electrical parts distributor based in Dallas. Y’all just let your mouse mosey on down to www.rexelusa.com [no hyphens] and lead it to “News” to select “Archives” from the drop-down menu. Click on “Motors & Drives” at the far left and you’ll be rewarded with a good read. By the way, Murphy authored a two-part article about drive harmonics that was published in Plant Services in late spring of 1999.