Power Supply Search: I/P AC: I/P DC: O/P Range: Power:
July 2009 - MTBF- Mean Time Between Failures or Might Take Brain Fodder
MTBF is often a confusing figure at the best of times, especially when it is not quantified by actual test results. PULS, a world leader for DIN Rail power design, have calculated and documented many different versions to help simplify this arguable figure.
MTBF stands for 'Mean Time Between Failures', but what does this really mean? The name would indicate that this is the average time between a power supply failing, which in turn could be assumed to be an estimated life time. This, however, is an incorrect assumption as the life time and MTBF are only related in that the MTBF is the statistical rate that the power supplies will fail within a given lifetime.
For example, if we take a power supply for instance with a 24 year MTBF, ignoring for the moment that this figure should be quantified by operating temperatures, output load and testing standards. This would give you an hour rate of 210,000Hrs rounded to the nearest thousand. Now assuming a common market warranty of 3 years we can statically calculate the number of failures within the warranty period. This is done by dividing the life time (3 years) by the MTBF; in this case it would give a figure of 0.125. This means 1.25 in every 10 units or in percentage form, 12.5% of all units may fail within 3 years.
Quantifying results is an important characteristic when noting lifetime or reliability. The simplest way to look at this is with food, a loaf of bread will last about one week if left out in the kitchen, however, if you put it in the freezer it will last a lot longer. The same is true when calculating MTBF figures, there are a number of different test standards and these can be done at half load or full load, at different temperatures all will give different values. PULS state all this required information on their data sheet and with the free UK technical support for customers it can be calculated to your required load and temperature levels.
PULS Dimension products boast calculated MTBF figures of over 1000,000Hrs or over 114 years. This again is statistical representation of the likelihood of a failure and if we compare it to the above example it shows 2.6 in every 100 units may fail within 3 years or alternatively 2.6%. This is almost 500% more reliable than the above example.
Harry Moore, Managing Director of PULS UK comments, 'We are always trying to provide the best efficiency, smallest size and now even the most reliable products to our customers. With failure cost being more dramatic than they have been in years, there are even more reasons to choose PULS!'
