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UL 2556中對絕緣耐壓測試有三種方式.
" C, A/ n S' f, R6.2 Dielectric voltage-withstand8 ?) [4 Z% e, ]) D& P- o& Y: I
6.2.1 Scope
4 A, U! x% {8 s3 D w. M8 XThis test establishes the methods for determining the dielectric voltage-withstand of a wire or cable.6 D4 l9 O9 O5 ]: l- i8 r7 m
6.2.2 Apparatus
0 U7 R1 l$ H$ ^$ kThe apparatus shall consist of
1 }6 K* h' ^, \1 g' s" Ja) an isolation transformer capable of supplying a test potential of 48 to 62 Hz, whose output. L9 j4 i: y- S' o# s
potential is continuously variable from near zero to at least the specified rms test potential;
$ d' @4 s2 S6 ^) E( ^4 s: J6 bb) a voltmeter having an accuracy of ±5%, on the high voltage side of the transformer. If! E6 J q4 |6 Q, R2 i7 a" I+ h" z
analog, it shall have a response time that does not introduce a lagging error greater than 1% of% A z3 s; E/ M" x0 Q' @, x8 J
full scale at the specified rate of increase in voltage; Z1 t+ N% ~5 E3 z3 e6 ~
c) a fault current indicator;
Y0 U' p8 N1 U( Zd) a forced-air oven as described in Clause 4.2.3 Item (i), having insulated bushings for
: i7 |; ]; E5 V t& `connection of the test voltage while the oven is closed;9 {6 M( H* {7 {! Q& R, f1 `0 c4 K
e) a temperature-measuring device with an accuracy of ±1 °C;
$ k, M& l* J4 A* `- S- Xf) a tank filled with tap water; and% g% J5 G) [" Q! m3 J; A0 c
g) a means of grounding, maximum impedance of 15W.+ T% x! r* [; E! X8 }
6.2.3 Preparation of specimens
3 ^6 H; }' \* M; g) N# l; x6.2.3.1 Method 1 (in water)
5 }8 J9 P$ h! iBoth ends of the individual conductors shall be made bare.: O% i, [: X, J% C( o: R
In preparing the wire for test, each end of the specimen shall be brought out well above the water level
0 ?! G7 ]" J7 K# ^3 Ein the tank, where applicable, and the covering removed from the surface of the insulation for a short3 Z) S) D2 s2 c8 _6 I
distance if necessary to prevent surface leakage. The temperature of the water in which the specimen is0 o7 p& W/ I$ f& {( h, Y1 K8 T. P
immersed need not be controlled unless specified in the product standard.& r; I/ t9 m; d% K+ J
Unless specifically required by the product standard, a shielded or metal-covered single-conductor) F/ w3 ?2 B$ Q( g$ H: V( y
specimen need not be immersed in water, the test voltage being applied between the conductor and the7 I; m. \% m* K# b( l
shield or metal covering.
N7 I+ v* k4 t4 N$ p) oUnless specifically required by the product standard, a multiconductor cable need not be immersed in5 ~! W7 e: v2 C& |3 ~
water, the test voltage being applied between each conductor and the electrode, consisting of all other( c: x( {! h1 b+ g
conductors connected together and to all shields and metal coverings, as applicable.8 Y8 \/ E E- m: ~
In all cases, the ends of the conductor of the specimen shall be spaced from the grounded electrode a
- v- Y: W7 t2 a* t* [sufficient distance to prevent corona or flashover at the ends during application of the test voltage.
3 W9 @( U7 `2 q; `8 E0 L6.2.3.2 Method 2 (in air)
5 e! V) L2 I/ C; f; tBoth ends of the individual conductors shall be made bare.: }; g% E# D' b& s, u
For a single-conductor cable, a grounding electrode, when not present as a component, shall be applied.1 j% m8 {) h& \5 o5 I% b
A snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable.
2 }" U3 G) W( X1 R$ v: a6 e6 T1 L) p. s6.2.3.3 Method 3 (in air at elevated temperature)3 d+ g. Z2 H2 ]+ @& U7 y7 |
Both ends of the individual conductors shall be made bare.: G, K5 M" c: }: w, ]7 F7 V
For a single-conductor cable, a grounding electrode, when not present as a component shall be applied.4 Z% t t+ C8 S3 q* c
A snug-fitting close-weave copper braid, a metallic tape, or graphite have been found to be acceptable. |
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