OSM_EE 13.7

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IEC60335试验指甲

Question:
Table 2 of 60950-22 gives examples how to reduce the pollution degree from 3 to 2 inside the enclosure of an outdoor enclosure.
: f8 V! K- S0 l7 C. {* q' VOne method is to use an enclosure meeting IP54.
& Q+ E1 Z, `( G/ g7 gIn EN 60529, for Dust Testing involving first characteristic numerals 5 and 6, its sub-clause 13.4 (Dust test for first characteristic numerals 5 and 6) states, Enclosures are of necessity in one of two categories:
' K$ S4 Y( W+ p% lCategory 1: Enclosures where the normal working cycle of the equipment causes reductions in air pressure within the enclosure below that of the surrounding air, for example, due to thermal cycling effects.
' q) |& `& N$ b( D  z% U# [Category 2: Enclosures where no pressure difference relative to the surrounding air is present.
Additionally, in 13.5.1 is stated, “The enclosure shall be deemed category 1 unless the relevant product standard for the equipment specifies that the enclosure is category 2.”
EN 60950-22 does not mention anything about the enclosure category – does this mean that only IP5X tested according to category 1 is acceptable?
0 C* d) F9 b( B' M- a" S& w7 \Decision:
8 T7 O, E8 R6 n3 h1 r( p, VOutdoor Enclosure. Since an outdoor enclosure does not consist of complete assembly, for IEC 60529 IP dust testing, the test method for Category 1 should be followed.
Outdoor Equipment. The test method, pressure to be applied - Category 1 or Category 2 should be determined based on:
[a] Does the product have an environmental/air handling system? (e.g fan, ventilation valve)
6 U9 I6 Z2 `& i" i; V4 k Is the product a sealed device with no internal environmental controls?
If a complete system with air handling system, testing should be based on the actual pressure differential in the equipment rather than that specified for category 1. For equipment with no environmental controls and air handling,category 2 method should be followed.
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