Why is relay reliability expressed in MCBF rather than MTBF like other electronic components?
Relay failures are primarily due to functional operation (cycling) rather than the amount of time accumulated while operating. A relay manufacturer cannot anticipate the number of cycles per hour the relay will be operated when installed in equipment. If the MTBF is required, the relay user can convert MCBF into MTBF by dividing the cycling rate (operations per hour) into the MCBF. • Is MCBF a guaranteed period of failure-free service? No. An MCBF has absolutely nothing to do with the minimum rated life of a relay. An MCBF is derived from live testing a large number of relays for their minimum rated life. The number of failures that occur during the testing are then divided into the total number of completed operations. • Do initial screening tests have any effect on the reliability of relays during the use life? Yes. Screening tests detect those failures, which would otherwise occur during the early life of a relay. This is why it is important to know what screening tests are performe
