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UL 1412
$ c% L9 ^& s2 H. M15 Overload Test
- t w6 A) u) o0 i, E7 c15.1 A resistor shall withstand the overload test described in this section without resulting in a fire.
# I, t. ? F5 o% _ u7 x15.2 A single layer of cheesecloth is to be wrapped around, and be in contact with, the resistor under test.
1 @! O; v6 m0 E0 C) mException: At the manufacturer’s option, the cheesecloth may be spaced 1/2 inch (127 mm) – or 1 inch
' i& t0 x; m5 L6 R! x8 N* s' p9 `* ~! I(25.4 mm) for a resistor rated greater than 10 W – from the resistor body as described herein. In this case,
2 i* W: P+ A+ W# w* R) o( pa positive spacing of 1/2 inch (or 1 inch, as appropriate) between the resistor body and combustible
0 ^$ L6 F' Q3 Omaterials is to be provided in the complete appliance. A single layer of cheesecloth is to be placed around
3 x4 y, s2 a: u6 V* ?! c$ ?the resistor under test to form a cylinder with open ends. The length of the cylinder is not to be less than
6 w% w1 J( o9 |1 ?three times the length of the resistor body and the diameter of the cylinder is to be such that the
- w8 n6 e+ V8 Z" l6 s- [cheesecloth is spaced 1/2 inch (or 1 inch, as appropriate) from the outermost part of the resistor body.. G+ _ ?3 G' X8 P' y% P
The resistor body is to be centered end-to-end within the cylinder and the longitudinal axis of the resistor
8 @1 y2 c. ^2 Dbody is to be coincident with the longitudinal axis of the cylinder.
; k- K, o* X; m8 O) I15.3 The resistor is to be connected to a 60-Hz variable voltage source of supply fused at 30 A. Prior to
0 G. [; o! [+ I9 P" s Xenergizing, the supply voltage is to be adjusted to produce rated current (or rated power dissipation) in
5 h( t1 J7 s* w& m3 Xthe resistor. At 1-minute intervals after energizing, the supply voltage is to be raised in steps of 2, 3, 4, 5,
, z* t' }7 ^, J$ @7 Q6 I# gand so forth, times that initial voltage until the resistor opens. In no case is the voltage rating of the resistor
) T# D3 ]: J6 Z7 l& Q5 U9 a, f! u1 Sto be exceeded.) ]. P: C+ _9 ?' d. I# M: ~
15.4 Five complete separate tests are to be made using new samples for each test.: y$ I/ v2 C6 s; c. {# @
15.5 The results are not acceptable if the cheesecloth flames./ Z% E# T3 o+ [+ V, r
15.6 The cheesecloth used for the overload test shall be untreated cotton cloth 36 inches (0.9 m) wide,
) m" e/ V* \# }5 f! Srunning 14 – 15 yd2 /lb and having what is known to the trade as a count of 32 by 28. |
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