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|  DSH 709/06# [) }/ }$ V/ T" X6 o- h1 h
2 {0 C7 a; {# j J: K& U B% f | Short circuit and overload protection
( F. @) o% S! B) w' o | 15.2; b3 n4 B9 Q6 P2 w9 e
| 61558-1(ed.2)5 j# d3 L7 K0 [. m$ n! G
|
& S0 ~6 W n: o" z1 r
Standard(s): IEC 61558-1/2005 No. Year
! g( q! Q' @+ bDSH
: b, J$ V: F1 Y3 K07090 b( t. G n! i; _4 e: g) P0 |
20085 f$ U: O* d2 A7 }6 P. \
Category: SAFE
2 n7 m. V+ h. N, T2 ~* j4 R6 OSubclause(s): 15.2
2 o6 \! b. z, l: X F0 qDeveloped by: ETF5
1 ~- H) Z/ u! P% d' _( I3 yOSM/LUM
2 d5 E6 m& G& p7 i% j+ TSubject: Short circuit and
7 B/ r/ | B, J( t/ Z' w- joverload protection2 X. r' f8 ]/ C/ p$ u
Key words:
* n0 E f9 M1 j0 e7 w- Transformers
7 c, S: Q5 I9 { F/ b4 x* U- Steady state conditions
5 X9 v' |* [8 u" @* V9 V- Short circuit' B/ U: X4 C' L5 e* M
Decision approved at the
# \: N1 q9 x7 s2 J. ^8 y* U46th CTL Plenary Meeting,7 x: `& I( t. j1 g; m' V
in 2009
6 v, T- C( b! [. u, lQuestion:
' C+ W" e! ^# E. K ?+ aInherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
3 i9 [$ a) ?# i( r6 K0 N% C& |steady-state conditions are reached.: x5 n3 x+ v. o3 P' r [$ @
In IEC 61558-1 “steady-state condition” is not explained. Referring to other standards the meaning of m- ]' W5 z! j' T7 ~, \9 M
“steady-state conditions” or “thermal stability” is that the change of temperature is less than 1°C per hour.: Z" a3 N4 @1 q! w
So following questions arise:
. H9 H0 E% v: E+ T8 r Z: ~1) Is it correct to record the temperatures after one hour when temperatures did not change (more8 v% ]) a8 {$ U( k8 {4 v) J: Y/ f
than 1°C/h)?
4 O9 N9 y6 b# r8 T0 P2) How shall an inherently short-circuit proof transformer be assessed when the above mentioned% E. R5 r' F8 ]1 K, M
requirements are fulfilled, but it is damaged 6h after reaching the steady state condition in a way) V7 a9 o, A' a T
where safety will be impaired (the transformer bursts).! F& ?' k- P8 ^7 h9 O
Decision:2 t, _0 W, W; _. a
1) Yes.
& S$ D8 ^* v8 ^* i* l5 u/ j& k" S+ g2) The transformer should not be accepted.
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1 O4 k+ u* x2 \: F$ A
Z8 _7 x, N& z* A+ B% x+ ^ |
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