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UL 1412
. r5 p0 F% H3 D& f3 T7 u0 n5 u15 Overload Test
/ J. T' r' U( b15.1 A resistor shall withstand the overload test described in this section without resulting in a fire.# q4 B9 I2 ~/ f( A! O' R
15.2 A single layer of cheesecloth is to be wrapped around, and be in contact with, the resistor under test.
; Y- z! B* r9 }, u; FException: At the manufacturer’s option, the cheesecloth may be spaced 1/2 inch (127 mm) – or 1 inch$ w' G3 K1 ?. y& @7 K2 F
(25.4 mm) for a resistor rated greater than 10 W – from the resistor body as described herein. In this case,7 F- F) M6 T+ D* {2 h* {5 D0 P
a positive spacing of 1/2 inch (or 1 inch, as appropriate) between the resistor body and combustible
: ?' j+ Q. c A$ b9 @materials is to be provided in the complete appliance. A single layer of cheesecloth is to be placed around
# I- S+ u' l8 Sthe resistor under test to form a cylinder with open ends. The length of the cylinder is not to be less than
7 B0 |* g1 E- Z9 L: N6 ?three times the length of the resistor body and the diameter of the cylinder is to be such that the
# K# c6 J8 g2 N; O( fcheesecloth is spaced 1/2 inch (or 1 inch, as appropriate) from the outermost part of the resistor body.
4 h/ d& u" n1 Y4 ]The resistor body is to be centered end-to-end within the cylinder and the longitudinal axis of the resistor
6 J6 O% o5 X8 Gbody is to be coincident with the longitudinal axis of the cylinder.
. p! g8 ^) h" Q$ b$ D. A15.3 The resistor is to be connected to a 60-Hz variable voltage source of supply fused at 30 A. Prior to
. X8 w& ?$ N! |; g3 `# d4 @energizing, the supply voltage is to be adjusted to produce rated current (or rated power dissipation) in
+ S0 D$ s8 D: M, rthe resistor. At 1-minute intervals after energizing, the supply voltage is to be raised in steps of 2, 3, 4, 5,
X! y b/ {& B5 A7 D' iand so forth, times that initial voltage until the resistor opens. In no case is the voltage rating of the resistor
8 o- C; A- Y' e/ T6 xto be exceeded.% b p8 @) o' f: ^
15.4 Five complete separate tests are to be made using new samples for each test.
l) m2 N# _( d2 Y5 U4 A) K. b15.5 The results are not acceptable if the cheesecloth flames., }/ ]! N9 i* k6 Y
15.6 The cheesecloth used for the overload test shall be untreated cotton cloth 36 inches (0.9 m) wide," d# H' ]& `0 `& D, f
running 14 – 15 yd2 /lb and having what is known to the trade as a count of 32 by 28. |
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