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|  DSH 709/06; ~+ d7 |" Q3 d4 K; Q
- d( T9 M; \7 ]& I/ h3 R | Short circuit and overload protection! {7 a0 t. t T5 E8 V$ v
| 15.27 W6 \; |" I! j! f% `
| 61558-1(ed.2)* k* Y. n8 X. }4 N: M
|
6 N% [& z* a$ {8 t3 l( H3 XStandard(s): IEC 61558-1/2005 No. Year; _/ F( B4 B5 }, ~
DSH
; @3 ?. w; @! B/ Y# ]0709
1 w: j2 x. Q$ B, L' k2008
! r0 l1 }9 d! h3 ^+ qCategory: SAFE
5 Y3 j8 p. u) O' B5 q* \Subclause(s): 15.2
* f$ D# Z* ?3 _7 \ _* XDeveloped by: ETF5
) q/ P# E `; cOSM/LUM5 @: B& q5 {8 H# K7 z" X
Subject: Short circuit and
/ q' A1 }$ r$ \# Z4 p7 w) K" F2 V7 _overload protection9 s, K. p. I7 w6 i
Key words:1 L- X: z& _/ x* D' g% a
- Transformers T0 `) l0 f# ?1 E; ^
- Steady state conditions
$ @ T, Q; o4 r W, h- Short circuit& ~, e8 j+ }5 T% K! A9 y3 N
Decision approved at the
2 d- _8 g# B2 u/ Z46th CTL Plenary Meeting,
& v- l6 v3 Y" ^6 f/ Oin 2009
/ ?3 U1 H* z& {$ n8 f' YQuestion:2 _) j; X, J$ v& M' e4 m
Inherently short-circuit proof transformers shall be tested by short-circuiting the output windings until- I, g& {" u- H- E
steady-state conditions are reached.
3 n' u8 M- M8 U6 L$ w9 {In IEC 61558-1 “steady-state condition” is not explained. Referring to other standards the meaning of
" b1 F2 T" X5 j7 \6 ^/ y z# n! i v' S1 V“steady-state conditions” or “thermal stability” is that the change of temperature is less than 1°C per hour.. @* u: ^/ g# p% n
So following questions arise:
# H) O B# }: P6 t1) Is it correct to record the temperatures after one hour when temperatures did not change (more
' _& B$ w" i, P" xthan 1°C/h)?6 n; X$ J0 W3 v) u! \; |9 t" V
2) How shall an inherently short-circuit proof transformer be assessed when the above mentioned
( g/ s- r \2 k5 Z" arequirements are fulfilled, but it is damaged 6h after reaching the steady state condition in a way
. Z# e0 b& C5 M. N" w1 \$ }$ \9 |* B7 iwhere safety will be impaired (the transformer bursts).+ }3 ]% A5 t( u6 h
Decision:
: N; C9 I0 V! `$ G) s+ y9 Y1) Yes.
+ @- i5 I9 d! g2) The transformer should not be accepted.3 ~9 v; |( o' ?# U* i( T
) w/ u9 V: ^$ F7 z) Z' I2 G/ n
( M: q7 p% Q$ t! t7 H5 h4 T |
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