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UL 2556中對絕緣耐壓測試有三種方式.
$ z- v3 w& }* T0 s2 l. n" n6.2 Dielectric voltage-withstand
2 i" H1 ^4 Z& q2 n8 B6.2.1 Scope1 T% _. ~2 l( X- h- {
This test establishes the methods for determining the dielectric voltage-withstand of a wire or cable.
8 M; d$ s' n& x. L, ~2 ` b& k6.2.2 Apparatus
* H g5 q3 v$ _; uThe apparatus shall consist of
6 \- _ w4 [" w. X/ x+ h3 [a) an isolation transformer capable of supplying a test potential of 48 to 62 Hz, whose output
* @- U0 I: f! S* x/ i3 @potential is continuously variable from near zero to at least the specified rms test potential;
. x( i9 Z4 k. Y. h& x- |b) a voltmeter having an accuracy of ±5%, on the high voltage side of the transformer. If
2 x5 @ T* t6 {7 r8 Ganalog, it shall have a response time that does not introduce a lagging error greater than 1% of
2 k3 @/ W) j% }full scale at the specified rate of increase in voltage;
+ x5 }; T3 S9 A) F/ Mc) a fault current indicator;
0 q1 F. x+ `- ^. V2 ~# qd) a forced-air oven as described in Clause 4.2.3 Item (i), having insulated bushings for9 T- ?+ C& a' D, h& E* V
connection of the test voltage while the oven is closed;1 ~1 P& s4 b1 R' i A# i* M+ T
e) a temperature-measuring device with an accuracy of ±1 °C;" T! o. Y- ~, j" A- V
f) a tank filled with tap water; and
2 U: }7 C0 ]8 }+ Yg) a means of grounding, maximum impedance of 15W.
, b4 R# g/ G: _& e) [+ |% v! e6.2.3 Preparation of specimens
( l7 _3 x: y' ^7 J9 e( |6.2.3.1 Method 1 (in water)
5 E- F2 H% v, D0 ABoth ends of the individual conductors shall be made bare.7 E1 u9 V G/ B/ q
In preparing the wire for test, each end of the specimen shall be brought out well above the water level, ~2 x. v: ?2 P4 n
in the tank, where applicable, and the covering removed from the surface of the insulation for a short6 c( w5 @5 e6 L2 Z
distance if necessary to prevent surface leakage. The temperature of the water in which the specimen is
' G. a4 t, w8 y0 ?: simmersed need not be controlled unless specified in the product standard.
0 k* x0 E+ o5 ?Unless specifically required by the product standard, a shielded or metal-covered single-conductor
9 {) ~4 Q4 p, [; Q, Q7 Bspecimen need not be immersed in water, the test voltage being applied between the conductor and the* B, k" O. P- ]1 f2 Q' a" ^+ L
shield or metal covering.
* Y m' H% @& x1 iUnless specifically required by the product standard, a multiconductor cable need not be immersed in
1 D# B6 H: g1 Cwater, the test voltage being applied between each conductor and the electrode, consisting of all other
x, p5 ]# [1 s2 }; zconductors connected together and to all shields and metal coverings, as applicable.% v$ r- w/ B0 Q8 a, c1 W
In all cases, the ends of the conductor of the specimen shall be spaced from the grounded electrode a% g: M% m2 H1 j0 [) ]9 _, N8 o
sufficient distance to prevent corona or flashover at the ends during application of the test voltage.
0 W/ E( D& _% O" l% n6.2.3.2 Method 2 (in air)
( h- t. G' K) [, ~1 Y* C; iBoth ends of the individual conductors shall be made bare.
2 I+ h$ `# l0 w$ IFor a single-conductor cable, a grounding electrode, when not present as a component, shall be applied.
7 T( J# k2 [" m' G7 E6 aA snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable.4 U# t9 W% [# E3 u+ }8 }. N# d) E& d
6.2.3.3 Method 3 (in air at elevated temperature)
7 v1 J5 y6 W; ]8 @Both ends of the individual conductors shall be made bare.- f+ Y3 G+ ?( `" H0 q0 J$ C: V
For a single-conductor cable, a grounding electrode, when not present as a component shall be applied.
* L( ~8 s9 U+ I3 ]( dA snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable. |
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