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What is the meaning of Continuous, Intermittent, Nb Cpt missing Qty, Nb Cpt Total Qty, and Ratio Nb Cpt Missing Qty, Nb Cpt Total Qty terminology in MTBF data?

Published date: 09 July 2019

Issue
What is the meaning of the following terminology in MTBF data?
Continuous
Intermittent
Nb Cpt missing
Nb Cpt missing * Qty
Nb Cpt Total * Qty
Ratio of Nb Cpt Missing / Nb Cpt Total

Resolution
In Schneider Electric FAQs containing MTBF data:

Continuous - the part is used in service for 24 hours a day and 7 days per week without stoppages. 100% operation rate per year (365d / year, 24h / day) - 12 power on/off per year (1 per month) - No stocking days

Intermittent - the part is used in an interrupted process (for example powered off during night, weekends and holidays). 46% operation rate per year (335d / year 12h /day) - 335 power on/off per year (1 per operating day) 30 stocking days

MTBF values are given in hours for a specific temperature in degrees Celsius.
The MTBF value of a part is calculated with MTBF of all components used in the part.

Nb Cpt Missing - the number of unique component types for which does not have known MTBF data that are used in the part (2 resistors of the same make and manufacturer counts as 1)

Nb Cpt Missing * Qty - the number of components in the product which does not have known MTBF data that are used in the part (e.g. 2 resistors of the same make and manufacturer count as 2)

Nb Cpt Total * Qty - total number of components used in the part

Ratio Nb Cpt Missing / Nb Cpt Total - the percentage of components (by quantity) that have unknown MTBF data in all the components that comprise the part.

For more information, please refer to the RDF2000 Reliability model (UTE C 80-810 standard).

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