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UL 1412
" u i) p3 }3 e: i( e. h15 Overload Test
8 l) S' Q- B# h: }7 U a. z15.1 A resistor shall withstand the overload test described in this section without resulting in a fire.
) k: t: _! R8 z4 \; b$ V15.2 A single layer of cheesecloth is to be wrapped around, and be in contact with, the resistor under test.
2 U% T2 Q9 j- CException: At the manufacturer’s option, the cheesecloth may be spaced 1/2 inch (127 mm) – or 1 inch
6 W/ U, d( y7 ~- s, J) Y% e(25.4 mm) for a resistor rated greater than 10 W – from the resistor body as described herein. In this case,, Q/ c+ g9 ~4 [) G( c9 L
a positive spacing of 1/2 inch (or 1 inch, as appropriate) between the resistor body and combustible
: \6 M! `9 F G2 G8 Imaterials is to be provided in the complete appliance. A single layer of cheesecloth is to be placed around
* w3 m# N+ h' T5 b) Gthe resistor under test to form a cylinder with open ends. The length of the cylinder is not to be less than
( r7 @) R* u) w4 c6 ]3 z" uthree times the length of the resistor body and the diameter of the cylinder is to be such that the
$ Z0 `3 {! C, x1 ?' Y i' P7 Icheesecloth is spaced 1/2 inch (or 1 inch, as appropriate) from the outermost part of the resistor body.3 G1 v8 L2 U7 S# I$ v
The resistor body is to be centered end-to-end within the cylinder and the longitudinal axis of the resistor0 v9 w3 M t6 U+ e7 V' a* B5 |
body is to be coincident with the longitudinal axis of the cylinder.
+ `1 H# w8 }& _15.3 The resistor is to be connected to a 60-Hz variable voltage source of supply fused at 30 A. Prior to( J ?9 K) b$ A7 ^" C
energizing, the supply voltage is to be adjusted to produce rated current (or rated power dissipation) in
- [+ I9 g1 c+ K' Nthe resistor. At 1-minute intervals after energizing, the supply voltage is to be raised in steps of 2, 3, 4, 5,8 q7 W# S4 U1 S0 a: v5 Q
and so forth, times that initial voltage until the resistor opens. In no case is the voltage rating of the resistor
C& f% u3 g0 s0 Q; D, Wto be exceeded.; ?1 E5 c; ~; u H2 [
15.4 Five complete separate tests are to be made using new samples for each test.! J$ ?, q% \8 x
15.5 The results are not acceptable if the cheesecloth flames." H/ l( q3 E; E; `
15.6 The cheesecloth used for the overload test shall be untreated cotton cloth 36 inches (0.9 m) wide,/ P; T& v) @1 E3 Z% Q
running 14 – 15 yd2 /lb and having what is known to the trade as a count of 32 by 28. |
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