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INTEGRATED DIAGNOSTIC SYSTEMFigure 1: In the endurance test room – the datafor the conventional life span calculation isacquired using the climate chamber.The new diagnostictool can determine theindividual service lifeof the fannot taken into consideration in this procedure.In order to make statistical statements concerningfans, it is enough to take into considerationthe service life of the rotor bearing. Failuresof the electronics or the motor winding are significantlysmaller and can normally be neglected.On this basis, ebm-papst developed a diagnostictool implemented in the fan that determines theindividual service life of the fan while taking intoconsideration the respective ambient and operatingconditions. This way the existing limitations ofthe operating statistics are completely redefinedby exact fundamental data and the latest methodsof calculation.New approach The new service life predictiontakes into account the individual history of the fanin its respective operation and thus statementsabout an expected remaining service life can bemade in individual cases using the applicationconditions. Changing temperatures (day/night cyclesor seasonal fluctuations) are taken into account,as are the accepted dust pollution on-siteand the actual speed. This data is used by theelectronics integrated in the fan to calculate theservice life (Figure 2).The new early failure detection is conceivedparticularly for users who can replace the fan onlyat high cost or at certain times (for example, re-Figure 2: Compact fans with high output andinternal self-diagnostics for service lifeService life or reliabilityService life and reliability are two terms thatare often used and equally easy to mix up. Servicelife, often abbreviated to L10, specifies aperiod in hours during which up to 10 percentof the devices will have failed. An L10 value of100,000 hours means that 90 % of tested deviceshave reached this run-time. In contrast,reliability is specified with the value Mean TimeBetween Failure (MTBF). Since fans normallycannot be repaired, a more apt designationwould actually be MTTF (Mean Time To Failure).Despite this, MTBF has become the expressionthat is most commonly used. Statements regardingMTBF values only apply during the plannedperiod of validity (e.g. usable service life).The failure rate can increase significantly afterthat due to signs of wear. A MTBF value of1,000,000 h (more than 110 years) means thatif 1,000 devices were running at the same time,one of them would fail every thousand hours,i.e. every 42 days (1,000 h * 1,000 =1,000,000 h).14techmag 01°2013