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UL 1412
. z7 B3 F- D9 M# _- I& _15 Overload Test
: _' ? m, p3 m1 I+ ~; q! @" r15.1 A resistor shall withstand the overload test described in this section without resulting in a fire.
( ^& p2 I% o/ s1 T' S" }" y' j# x* m15.2 A single layer of cheesecloth is to be wrapped around, and be in contact with, the resistor under test.8 r+ z+ d- w, X. c
Exception: At the manufacturer’s option, the cheesecloth may be spaced 1/2 inch (127 mm) – or 1 inch/ C8 Z7 K( `6 h) j5 G# i
(25.4 mm) for a resistor rated greater than 10 W – from the resistor body as described herein. In this case,7 ^6 v$ q4 f( q4 Q
a positive spacing of 1/2 inch (or 1 inch, as appropriate) between the resistor body and combustible5 [5 Q5 b& @5 O
materials is to be provided in the complete appliance. A single layer of cheesecloth is to be placed around) B! ]. n. Z K, G: l: u5 x
the resistor under test to form a cylinder with open ends. The length of the cylinder is not to be less than
6 ~7 u) \4 C f9 O% Tthree times the length of the resistor body and the diameter of the cylinder is to be such that the9 f4 n, U& _- C; o9 o: ~$ S1 k$ d$ Q
cheesecloth is spaced 1/2 inch (or 1 inch, as appropriate) from the outermost part of the resistor body.$ Q( B, r( F/ B5 e& O4 {
The resistor body is to be centered end-to-end within the cylinder and the longitudinal axis of the resistor; Q# s; r" ]5 I0 }" I
body is to be coincident with the longitudinal axis of the cylinder.
" h( Y9 m, E- p, Y3 _3 {( {; x% {; y15.3 The resistor is to be connected to a 60-Hz variable voltage source of supply fused at 30 A. Prior to
* @2 ]; U4 M- o, a# |' henergizing, the supply voltage is to be adjusted to produce rated current (or rated power dissipation) in
! I* y' L8 S2 m' rthe resistor. At 1-minute intervals after energizing, the supply voltage is to be raised in steps of 2, 3, 4, 5,# k% Q" l+ b5 n
and so forth, times that initial voltage until the resistor opens. In no case is the voltage rating of the resistor9 I+ X4 h# z. t1 H5 r! V' [+ k" A) a' T
to be exceeded.$ ?+ R G$ O c6 G
15.4 Five complete separate tests are to be made using new samples for each test.( `) L: k. F: @1 |) I+ ^/ ^0 Y& d
15.5 The results are not acceptable if the cheesecloth flames.
4 F3 U: e$ n$ Y+ h u# ^15.6 The cheesecloth used for the overload test shall be untreated cotton cloth 36 inches (0.9 m) wide," Q" D2 M/ ^5 Q5 H) M
running 14 – 15 yd2 /lb and having what is known to the trade as a count of 32 by 28. |
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