IEC 60947-5-4-2019 pdf free.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.
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 continuousmonitoring of the contacts under test.
For the basic method (see 6.1.1)， the voltage drop between the terminals of the closedcontact(steady state – see 3.1.9) is measured for each operation and compared to aspecified threshold.
Iln 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 conditionsas defined in clause 8. The measurement of the voltage drop is made directly on theconnecting terminals of the contact(s) or on the connecting terminals of the load (see 6.1.2).
ln the basic and alternative methods recommended here (see 6.1.1 and 6.1.2), the contactsunder 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.
lt may be possible to test the contact(s) in particular environments (dry heat, dust, damp heat,H,S,etc.). Such environments shall be agreed between the user and the manufacturer，andshall be chosen from those defined in the lEC 60068-2 series (see clause 8).
ln the basic method, tests are made with direct current.Precautions concerning measurementof 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.
To ensure an adequate statistical estimate of the failure rate， eight or more contacts of thetype to be tested shall be tested.
NOTE Where applicable, both make and break contacts should be tested.
The number of operating cycles of the test shall be at least 25 %， and not more than 100 %，of the durability with the number of operating cycles at low energy stated by the manufacturer. Unless otherwise stated, this stated number is the mechanical durability.
Means of verification of the operating sequence,with special attention to the state of the contact sunder test, and calibration of measuring devices shall be included in the test equipment.IEC 60947-5-4 pdf download.