DSH 613 The air speed in the low temperature test cabinet for testing voltage ma
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The air speed in the low temperature test cabinet for testing voltage maintained thermal cut-out
17.16.108
60730-2-9(ed.1)
Question:
In practice, it is found that the test results were dramatically affected by the air speed of the cabinet when conducting the test of clause 17.16.108 of IEC 60730-2-9:2004, Ed. 2.2 in operated condition.
In the operated condition the contacts of the voltage maintained thermal cut-out remain open position by the heat generated by the PTC element. The faster the air speed in the test cabinet, the more heat generated by the PTC taken away by the air flow. This will reduce the temperature of the thermal cut-out which will make the thermal cut-out close.
Decision:
The test should be conducted in a static-air test cabinet or in a box which protects the samples from the air flow.
The required temperature (- 20°C) should be measured 50 mm beside the test samples (similar to the requirements according to clause 14.7 of IEC 60730-1)
During the examination of several samples in the test cabinet or box it is to be observed that the samples don't affect themselves among each other.
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