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UL 1412
+ Y1 e* d+ S3 b7 D' i1 e15 Overload Test
& ?# Q n8 S" Z( Y15.1 A resistor shall withstand the overload test described in this section without resulting in a fire.6 k4 Z4 v8 A! L
15.2 A single layer of cheesecloth is to be wrapped around, and be in contact with, the resistor under test.
; j" n/ N- B8 K$ |' q" o. k; d/ iException: At the manufacturer’s option, the cheesecloth may be spaced 1/2 inch (127 mm) – or 1 inch' s) J9 y/ T8 A
(25.4 mm) for a resistor rated greater than 10 W – from the resistor body as described herein. In this case,
2 A1 U; Z6 \& Q" Ea positive spacing of 1/2 inch (or 1 inch, as appropriate) between the resistor body and combustible
# n5 E5 r% o0 l gmaterials is to be provided in the complete appliance. A single layer of cheesecloth is to be placed around& I: a1 n4 ]4 m8 j+ a% H
the resistor under test to form a cylinder with open ends. The length of the cylinder is not to be less than
! g$ }% s8 u$ Z& P/ y% S' d3 Sthree times the length of the resistor body and the diameter of the cylinder is to be such that the5 P, L0 v' l$ H# n" S5 P" q
cheesecloth is spaced 1/2 inch (or 1 inch, as appropriate) from the outermost part of the resistor body.
& C1 c' \" [" }9 |) V9 [/ j4 BThe resistor body is to be centered end-to-end within the cylinder and the longitudinal axis of the resistor7 X' `* t9 F- I& S: O+ Q' C
body is to be coincident with the longitudinal axis of the cylinder.
# z' j9 S9 k/ K6 l& S15.3 The resistor is to be connected to a 60-Hz variable voltage source of supply fused at 30 A. Prior to
( l3 o, j: q9 P! ?4 C; Renergizing, the supply voltage is to be adjusted to produce rated current (or rated power dissipation) in' V6 f! N9 V7 L' A/ t. U: \( r7 g
the resistor. At 1-minute intervals after energizing, the supply voltage is to be raised in steps of 2, 3, 4, 5, ?$ s; K( }0 |' M4 h
and so forth, times that initial voltage until the resistor opens. In no case is the voltage rating of the resistor9 O5 Y6 g- j' u/ t! `9 z
to be exceeded.8 n/ D. H6 S& V! R
15.4 Five complete separate tests are to be made using new samples for each test.
4 E. T& v" H, p. z15.5 The results are not acceptable if the cheesecloth flames.
3 ]$ C" ?- _7 u K6 ]15.6 The cheesecloth used for the overload test shall be untreated cotton cloth 36 inches (0.9 m) wide,
7 J$ c1 V7 J% h: e2 @; U! ]running 14 – 15 yd2 /lb and having what is known to the trade as a count of 32 by 28. |
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