MTBF for CAC Products Rev D
1
ABB Drives MTBF for CAC Products Technical Description 3AFE Dept. Project CAC Status Date 10.7.2009 Author KUUSISTO LAURI Status APPROVED/DAVIDSAINEN JANNE Revision D Page 1 / 1 MTBF calculation method MTBF (Mean Time Between Failures) is calculated using method presented in MIL-HDBK-338B. Method is based on utilizing field failure data for obtaining the MTBF figure. MTBF week for a set of drives manufactured during certain week is calculated as: units failed of number r time operating total t T r t T MTBF week = = = ) ( ) ( Operating time is calculated to be the time from the manufacturing date to the observation date af- ter substracting a) freight delay from manufacturing plant to central stock (12 weeks) AND b) stocking and commissioning delay (26 weeks). Total operating time T(t) is obtained by multiplying operating time with the number of units manu- factured. Maximum operating time is limited due to units under warranty. Number of failed units (r) is based on warranty statistics – all failure cases including those caused by wrong usage or environmental problems are included in the figure. MTBF is calculated only for units under warranty, since reliable failure data for units beyond warranty does not exist. MTBF is calculated from weekly values MTBF week as a weighted average by using the number of manufactured units as weighting factor: week i i n i i i ave MTBF x weekly units produced of number w units produced of number total W x w W MTBF = = = = ∑ =1 1 MTBF calculation result Product family MTBF ACS55 > 50 years ACS150 > 50 years ACS350 > 50 years ACS550 > 50 years Calculations are based on data available on week 26, 2009 Note1 Limiting MTBF calculation only to units under warranty possibly decreases MTBF value due to limiting the maximum operating time. Note2 Calculating MTBF value for new products possibly gives too pessimistic values due to by nature limited operating time. Also calculation time is limited due to this. Note3 MTBF values have been updated in rev B (9.6.2008) due to changed calculation methods in manufacturing quantities. Note4 Production of ACS50 has stopped in March of 2008. MTBF value is now calculated for its successor ACS55
description
MTBF ABB
Transcript of MTBF for CAC Products Rev D
-
ABB Drives
MTBF for CAC Products Technical Description
3AFE
Dept.
Project
CAC
Status Date
10.7.2009
Author
KUUSISTO LAURI
Status
APPROVED/DAVIDSAINEN JANNE
Revision
D
Page
1 / 1
MTBF calculation method MTBF (Mean Time Between Failures) is calculated using method presented in MIL-HDBK-338B. Method is based on utilizing field failure data for obtaining the MTBF figure. MTBFweek for a set of drives manufactured during certain week is calculated as:
unitsfailedofnumberrtimeoperatingtotaltT
rtTMTBFweek
==
=)(
)(
Operating time is calculated to be the time from the manufacturing date to the observation date af-ter substracting
a) freight delay from manufacturing plant to central stock (12 weeks) AND b) stocking and commissioning delay (26 weeks).
Total operating time T(t) is obtained by multiplying operating time with the number of units manu-factured. Maximum operating time is limited due to units under warranty. Number of failed units (r) is based on warranty statistics all failure cases including those caused by wrong usage or environmental problems are included in the figure. MTBF is calculated only for units under warranty, since reliable failure data for units beyond warranty does not exist. MTBF is calculated from weekly values MTBFweek as a weighted average by using the number of manufactured units as weighting factor:
weeki
i
n
iiiave
MTBFxweeklyunitsproducedofnumberwunitsproducedofnumbertotalW
xwW
MTBF
===
= =1
1
MTBF calculation result
Product family MTBF
ACS55 > 50 years
ACS150 > 50 years
ACS350 > 50 years
ACS550 > 50 years Calculations are based on data available on week 26, 2009 Note1 Limiting MTBF calculation only to units under warranty possibly decreases MTBF value due to limiting the maximum operating time. Note2 Calculating MTBF value for new products possibly gives too pessimistic values due to by nature limited operating time. Also calculation time is limited due to this. Note3 MTBF values have been updated in rev B (9.6.2008) due to changed calculation methods in manufacturing quantities. Note4 Production of ACS50 has stopped in March of 2008. MTBF value is now calculated for its successor ACS55
MTBF calculation methodMTBF calculation result
![[organization name] MTBF and MTTR Downtime Dashboard KPI … · 2017. 10. 15. · [organization name] MTBF and MTTR Downtime Dashboard KPI MTBF MTBF Nov Corrective action ID ATI)](https://static.fdocuments.in/doc/165x107/610e0b6c168138163b1c1b7f/organization-name-mtbf-and-mttr-downtime-dashboard-kpi-2017-10-15-organization.jpg)
