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It comes from UL 746C% B9 B: @( f" @7 V _) T
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55DV.4.1 In addition to the other requirements in this Standard, flammability, mechanical
" B; J" g; ~ n2 cabuse and mold stress tests shall be conducted. Polymeric ENCLOSURES and covers shall2 u: v+ }6 B9 T( ~3 n, d" e4 h9 Q3 C y
comply with the requirements for resistance to impact and drop as indicated below, and
2 H+ a0 `. h6 v! ^the requirements for mold stress release distortion, in the Standard for Polymeric Materials
+ r' O. \4 O3 n% ~3 [' p! ?! f5 d- Use in Electrical Equipment Evaluations, UL 746C.: ?" A% B/ z3 Q
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In UL 746C, the standards says% X8 Z/ |3 y% O0 @
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58.3 Each of three samples of the appliance shall be subjected to a single impact of the value shown in
/ y# |- L) H) D" N% yTable 58.1 for the applicable equipment type, on any surface that can be exposed to a blow during
6 K" O9 W+ j) Bintended use. This impact is to be produced by dropping a steel sphere, 50.8 mm (2 inches) in diameter,6 @! R) a, v+ ~) V2 F" g1 S
and weighing 0.535 kg (1 .I8 Ib) mass from the height necessary to produce the specified impact as shown
# D. `1 l; y0 C- o, N. A- o, K4 J5 T- _in Figure 58.2. The steel sphere shall strike the surface in a location different from those in the other two# V2 Z; I8 B( L
impacts. For surfaces other than the top on an enclosure, either the sample could be supported on the$ e- ~. t' z! v+ \. y3 s& R6 y! z
side and subjected to the ball impact mentioned above, or the steel sphere is to be suspended by a cord
: m$ l8 {& T& ?$ c- m/ R, r2 Y- Dand swung as a pendulum, dropping through the vertical distance necessary to cause it to strike the
* L& J3 t1 m: Q* @" c p: tsurface with the specified impact as shown in Figure 58.2. Three samples shall be employed for the tests; u9 M* |# k* O. n: w* m3 O- a; K
in the equipment restrained mode. However, if the manufacturer so elects, fewer samples may be used2 `- o+ W" k1 T" ^2 E
in accordance with Figure 58.1. The overall performance is acceptable upon completion of any one of the
+ Y, j9 V, a% `1 H# i) [9 J; esequences represented in Figure 58.1. |
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