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UL 1412
: a D: D) a2 v7 l1 K15 Overload Test% b; \$ w4 r$ j' X0 {# F
15.1 A resistor shall withstand the overload test described in this section without resulting in a fire.7 L- ]1 k1 S4 ^/ F+ l( P
15.2 A single layer of cheesecloth is to be wrapped around, and be in contact with, the resistor under test.
3 ~5 F) E- x" a" g4 `Exception: At the manufacturer’s option, the cheesecloth may be spaced 1/2 inch (127 mm) – or 1 inch1 { X$ N8 G7 Y4 s0 d" c
(25.4 mm) for a resistor rated greater than 10 W – from the resistor body as described herein. In this case,3 H: H# ]) p# p& f
a positive spacing of 1/2 inch (or 1 inch, as appropriate) between the resistor body and combustible
( x! e! c% f2 _3 ^$ Smaterials is to be provided in the complete appliance. A single layer of cheesecloth is to be placed around+ ?3 W! j- r' w% L* O, y7 e
the resistor under test to form a cylinder with open ends. The length of the cylinder is not to be less than" L- G' s/ K' r5 e! F
three times the length of the resistor body and the diameter of the cylinder is to be such that the
h" I5 G3 a$ ?) E8 c& Jcheesecloth is spaced 1/2 inch (or 1 inch, as appropriate) from the outermost part of the resistor body.
/ P: V8 b: Y5 |: {' c, ]( c& K8 wThe resistor body is to be centered end-to-end within the cylinder and the longitudinal axis of the resistor
4 E( Z7 V0 Z/ B' m6 hbody is to be coincident with the longitudinal axis of the cylinder.
. ~& e: T9 |; e- x; ~( Y15.3 The resistor is to be connected to a 60-Hz variable voltage source of supply fused at 30 A. Prior to
3 k7 s! ?; {% J+ venergizing, the supply voltage is to be adjusted to produce rated current (or rated power dissipation) in6 L0 w; Q8 ^& t* a0 Z0 U
the resistor. At 1-minute intervals after energizing, the supply voltage is to be raised in steps of 2, 3, 4, 5,
8 H% {, Q- B/ c# @& W5 B. T2 Oand so forth, times that initial voltage until the resistor opens. In no case is the voltage rating of the resistor0 d/ r+ i4 t5 n& Q" v8 }8 w# T% j
to be exceeded.
! z1 S0 |( B1 \) }2 r4 A' [15.4 Five complete separate tests are to be made using new samples for each test.
7 H) N* y1 @& c( t- X. O15.5 The results are not acceptable if the cheesecloth flames.. `7 n7 _3 L& _. O
15.6 The cheesecloth used for the overload test shall be untreated cotton cloth 36 inches (0.9 m) wide,) {0 @: t7 P3 ?& r! a' t' p) h- P
running 14 – 15 yd2 /lb and having what is known to the trade as a count of 32 by 28. |
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