IEC 60947-5-4:2002 pdf download

IEC 60947-5-4:2002 pdf download.Low-voltage switchgear and controlgear -Part 5-4: Control circuit devices and switching elements -Method of assessing the performance of low-energy contacts – Special tests.
3.1.4
defect
non-fulfilment of an intended requirement or an expectation for an entity, including one concerned with safety
NOTE The requirement or expectation should be reasonable under the existing circumstances.
3.1.5
observed failure rate ob
for a stated period in the life of an item, ratio of the total number of failures in a sample to cumulated observed number of cycles on that sample. The observed failure rate is to be associated with particular and stated numbers of operating cycles (or summation of operating cycles) in the life of the item and with stated conditions
3.1.6
assessed failure rate
failure rate of an item determined by a limiting value or values of the confidence interval associated with a stated confidence level, based on the same data as the observed failure rate of nominally identical items
NOTE 1 The source of the data should be stated.
NOTE 2 Results can be accumulated (combined) only when all conditions are similar.
NOTE 3 The assumed underlaying distribution of failures against time should be stated.
NOTE 4 It should be stated whether a one-side or a two-side interval is being used.
NOTE 5 Where only one limiting value is given, this is usually the upper limit.
3.1.7
constant failure rate period
that period, if any, in the life of a non-repaired item during which the failure rate is approximately constant
[1EV 191-10-09]
NOTE In reliability engineering, it is often assumed that the failure rate is constant, that is that the times to failure are distributed exponentially.
3.1.8
controlling unit
equipment generating commands to run a specified test sequence controlling synchronization and the flow of orders (such as starts, measurements, stops)
3.1.9
steady state (of the contacts after closing)
state of the contact after mechanical stabilization (after operation bounces)
3.1.10
load
device which is to be controlled by the contact under test
3.1.11
duty ratio
ratio, for a given time interval, of the on-load duration to the total time
[1EV 151-04-13]
4 General principles
A method of assessing the performances of low-energy contacts by special tests is proposed. As the failures of such contacts are of a random nature, the method is based on a continuous monitoring of the contacts under test.
For the basic method (see 6.1.1), the voltage drop between the terminals of the closed contact (steady state — see 3.1.9) is measured for each operation and compared to a specified threshold.
In the alternative method, the behaviour of the load is monitored at each operating cycle.
The measurement is performed under constant voltage U (see figures 2 and 3). The contact(s) under test is (are) mounted and connected as in normal service and under ambient conditions as defined in clause 8. The measurement of the voltage drop is made directly on the connecting terminals of the contact(s) or on the connecting terminals of the load (see 6.1.2).
In the basic and alternative methods recommended here (see 6.1.1 and 6.1.2), the contacts under test switch (make and break) the load.
For tests without switching the load, the analysis may be performed on the same equipment. The testing equipment for this purpose should, therefore, be designed accordingly.
It may be possible to test the contact(s) in particular environments (dry heat, dust, damp heat, H2S, etc.). Such environments shall be agreed between the user and the manufacturer, and shall be chosen from those defined in the IEC 60068-2 series (see clause 8).
In the basic method, tests are made with direct current. Precautions concerning measurement of low voltage shall be taken (for example, the use of shielded cables).
When the test is performed on a load, care must be taken to avoid voltage drops other thancontact voltage drop (use of stabilized power supply).
Any external influence liable to affect the results (such as vibrations) shall be avoided.