|
UL 1412
6 [$ H+ a1 q3 x, W9 Z7 m15 Overload Test% W2 g# T6 v4 I6 }5 B9 i |
15.1 A resistor shall withstand the overload test described in this section without resulting in a fire.
1 E3 y( W5 r2 j" Z! g, b15.2 A single layer of cheesecloth is to be wrapped around, and be in contact with, the resistor under test.
4 k% ?" ]% w" g8 nException: At the manufacturer’s option, the cheesecloth may be spaced 1/2 inch (127 mm) – or 1 inch( U( E! l0 b! Q
(25.4 mm) for a resistor rated greater than 10 W – from the resistor body as described herein. In this case,3 w! C2 B: d8 J" f7 N& r/ X# u
a positive spacing of 1/2 inch (or 1 inch, as appropriate) between the resistor body and combustible/ a1 a/ r5 ~, H8 B+ V
materials is to be provided in the complete appliance. A single layer of cheesecloth is to be placed around
- {# ~, \2 I- @9 s$ C- |the resistor under test to form a cylinder with open ends. The length of the cylinder is not to be less than
: {! u A" H) J0 Q$ b% E* [three times the length of the resistor body and the diameter of the cylinder is to be such that the/ }8 |1 G2 i) g# S j6 q8 B
cheesecloth is spaced 1/2 inch (or 1 inch, as appropriate) from the outermost part of the resistor body.
- T \9 O4 z7 g" o* c' ?The resistor body is to be centered end-to-end within the cylinder and the longitudinal axis of the resistor
) q; t# P1 F R% @! Gbody is to be coincident with the longitudinal axis of the cylinder.
% o# W0 J$ d& u2 N3 Z4 b' q15.3 The resistor is to be connected to a 60-Hz variable voltage source of supply fused at 30 A. Prior to
3 J3 j, ` Z% X Wenergizing, the supply voltage is to be adjusted to produce rated current (or rated power dissipation) in& q* w! J7 c5 `8 C2 z
the resistor. At 1-minute intervals after energizing, the supply voltage is to be raised in steps of 2, 3, 4, 5, E, ^/ l e: s* E. s" @/ F
and so forth, times that initial voltage until the resistor opens. In no case is the voltage rating of the resistor- M) W: f: F% w+ G; ?' n: S1 S
to be exceeded.2 W5 i6 d- I0 P! ^9 i9 J2 T" m
15.4 Five complete separate tests are to be made using new samples for each test. P; L8 R* m, S5 N0 T; H
15.5 The results are not acceptable if the cheesecloth flames.
5 U* u% g% @. M# h4 C5 F' `( W15.6 The cheesecloth used for the overload test shall be untreated cotton cloth 36 inches (0.9 m) wide,$ B: d" |6 f. v6 t- u
running 14 – 15 yd2 /lb and having what is known to the trade as a count of 32 by 28. |
|