Plant Services - August 2007 - (Page 46) Save some green. RELIABILITY Motors Internal hardware Figure 3. Double-capacitor, single-phase induction motor (left) and centrifugal switch (right). LubeSite spring-powered greasers are refillable and reusable. Which is great for our environment. But what’s also great is that it will only cost you 20¢ of grease every three months to keep the reservoir full. Which is great for your bottom line. So anyway you spin it, switching to LubeSite will leave you seeing green. www.lubesite.com Falk Complete Solution - 3.27 x 4.89.qxp 7/25/2007 induction-run single-phase motor. The start winding is usually an auxiliary winding intended for starting the motor and is disconnected from the power source by the centrifugal switch after the motor attains a given speed. An endurance test might involve cycling the motor on and off rapidly under load to subject the starting components to severe stress. Also, the rapid cycling subjects the motor to the inrush current and severe electromechanical forces that can be hard on windings that aren’t properly secured. These forces can elevate mechanical stresses on the motor assembly, including the mounts. Rapid cycling can overheat the motor windings and bearings, thereby accelerating 1 11:58 AM Pagemotor failure. The tests must be designed so the failure mechanisms of interest are accelerated. This means that failures unrelated to the mechanism under consideration must be ignored. FALKTM DRIVE ONE® The complete drive solution! Large motors defy testing It’s impractical to subject multiple large motors to the previous test regimen. Instead, historical data on the motors operating in the plant would be useful. But, only a few plants keep sufficiently detailed records of their motors and failures. Also, in a typical plant, the number and types of motors are so varied, manufacturers are so different, and motors operate in such different conditions with different maintenance practices over different time periods that it’s debatable whether a statistical number for MTBF would be meaningful for quantifying reliability. To minimize the cost of reliability, some users perform vendor qualification testing to provide some assurance for new motors they are considering. This involves a battery of Falk Drive One has the complete solution for conveyors, mixing, pumping, and most heavy duty drive applications. Call for details USA: 414-342-3131, South America: 56-2-231-5647, Europe: 44-1484-401842, Asia-Pacific: 65-6-444-0388, China: 86-21-64977890, Australia: 61-2-4962-8000 More resources at www.PlantServices.com/thismonth Motor brush life – “Brush life in DC motors” Vibration analysis basics – “Vibration analysis: what does it mean?” Dynamic balancing – “Does your machinery have the shakes?” Efficiency – “Conserving electricity with premium-efficient motors” Protective relays – “Don’t fade to black” Predictive maintenance – “Thermography’s role in motor monitoring” For more, search www.PlantServices.com using the keywords bearing, motor and winding. www.PLANTSERAugust 2007 www.rexnord.com 1-866-REXNORD 46 http://www.lubesite.com http://www.lubesite.com http://www.PlantServices.com/thismonth http://www.rexnord.com http://www.PlantServices.com http://www.rexnord.com http://www.PlantServices.com
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