Plant Services - August 2007 - (Page 43) RELIABILITY Motors L ike plastic cards, in many regards the electric motor fits the phrase “buy now, pay later.” e initial cost of the motor is a negligible fraction of its total cost of ownership. Minimize the cost of ownership by using only highly efficient motors and paying attention to costs associated with unreliable motors driving your equipment. Motors are central to the operation of many industrial processes and motor failure almost inevitably leads to equipment failure. One reason motor reliability is important in the industrial sector is the huge costs associated with lost production and downtime. Motor reliability is crucial to equipment operation and smooth-running processes, and an unreliable motor can be costly. study by EPRI confi rm that bearing failure is the leading reason for motor failure. Together, bearing and winding failures constitute at least 60% of all motor failures. e survey on large motors also reported that 37% of bearing failures and 33% of winding failures occur during normal plant operation. Plant and maintenance personnel don’t get excited when a motor fails in normal operation and they’d rather be working the other shift when it happens. Plant professionals don’t get excited when a motor fails in normal operation but they’d rather be working another shift when it happens. A system to detect incipient faults and warn of imminent failure on every motor is too costly, so such systems are applied only to critical motors. erefore, some failure rate is inevitable in normal operations. How many motor failures can the plant tolerate? Whether the issue is large motors operating in plants or small motors 43 Why motors fail Over many years, we’ve learned which motor components fail most often. Most issues related to induction motors, the industrial workhorse, apply to other motor types as well. It’s well known that bearing failure is the predominant motor failure mode, followed closely by winding failure. A survey by the IEEE subcommittee on power system reliability on large industrial and commercial motors and an independent A .PLANTSERVICES. http://www.plantservices.com
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