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  1. qassure

    Calculation of FIT or MTBF

    There are various means to find out the MTBF. Some time we conduct two types of test to find out the MTBF,. One is time terminated test and other is failure terminated test. The above problem can taken under time terminated test. No. of test samples - 1 Million Hrs tested - 10000 Hrs Failures -...
  2. qassure

    Ruston Gas turbine cranking battery

    Ni-cad cells are costly, at the same time it has long life. it is mostly used aircrafts, metro tarins etc, due to the requirement of high starting current. presently, SAFT (France) is manufacturing Ni-cad batteries for every application which includes electric cars. --QA
  3. qassure

    Ruston Gas turbine cranking battery

    Hi rraghunath sealed cylidrical ni-cads or low maintenance ni-cads has long life and more efficient. but the peak current requirement decides the selection of batteries. Ni-cads are capable of delivering up to 10C rate (10 times of their Ah rating) for about 20 seconds and 25C rate for about 2...
  4. qassure

    No output on generator

    You may as well check the insulation of the exiter field coils. Sticky brushes in the brush holder, dirty slip rings also the most probable causes.
  5. qassure

    Read any good books lately?

    You may read the 'Art of War' by Sun Tzu 'Tactics' by Edward de Bono.
  6. qassure

    How To Apply for a Lower Position

    Have confidence in you. What is life with out chalenges. You should go for, and only go for Sr. ME position only. Take it up and let's see what comes. My best wishes Qassure
  7. qassure

    time to failure?

    It may please be noted in my reply above, i have put Lambda symbol which has turned as (?). KIndly assume it as Lambda.
  8. qassure

    time to failure?

    MTTF (Mean Time To Fail) is the reciprocal of the Hazard rate Function or Failure rate(?)of a component or module. 1/?t is the unit of time per failure of that component or module.
  9. qassure

    45kva transformer, 380 primary to 208 secondary

    Hi desertsheik! you have not specified the load or the KVA rating of the transformer. How ever the following formulae may be used for rough estimate. F.L Secondary current= KVA rating X 1000/Secondary Voltage F.L Primary current=F.L.Secondary currentXTransformer ratio Transformer ratio =...
  10. qassure

    Ferrite Beads

    Ferrite beads are used to prevent the Electro-Magnetic Interference (EMI). Most of the power supply modules / PCBs have these ferrite beads in the input lines. These beads can be put along with the input connector (i.e. at the backside of the connector pins)instead of PCBs. presently coloured...
  11. qassure

    please clarify to me

    you may collect the data on time (operating) between the previous failures of the same equipment or similar type of the equipmet. more the number of data better the analysis. From the above data you can get MTTF (Mean time to fail). In the absence of any data you can resort to reliability...
  12. qassure

    environmental stress screening of electronic components

    Thank you Mr. IRstuff for your reply. Generally, We carry out thermal cycling with 5Deg.C per minute rise / fall in temperature for 10 cycles for a module with pre and post vibration. In case of PCBs thermal shocks used to be given. The severity of temperature at high or low depends on the...
  13. qassure

    environmental stress screening of electronic components

    presently COTS (commercially off the shelf) components are prefered than MIL approved components, due to cost, availablity and other factors. Environmental steree screening (ESS) is carried out on these components to weed out the infant mortality (i.e. to remove the components which are likely...
  14. qassure

    total technical life (TTL)

    Howmany MTBFs can be in Total Technical Life (TTL)of a component. In other words from the given MTBF is it possible to calculate TTL. Please tell me how. Also how to select a component to meet the design life of a electronics system and how to prove it.
  15. qassure

    sonar system MTBF

    Apart from probability methods, tests like time terminated test or failure terminated test can be conducted to find the MTBF. Since these tests costs time and money, how important is the system reliabilty may be the diciding factor for finding MTBF in this case.

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