& I$ O/ V% y4 o- y; i& s" U$ Y) R. v! @) IStandard(s): 3 ]. H- A/ x! U% mIEC 61558-18 m1 V4 e# j [) \ L& v. ~
All editions : M8 u& N, ^: {, I' r9 \Subclause(s): 0 J$ |2 H7 H0 y; v& m4 ?15.2 9 a. \- l1 D* a6 c' p' f7 C, qNo. Year % o3 {) W1 h0 y) m0 o0 L3 aPDSH4 x9 M# Q* | I O- j
1021 2010 / a3 a0 G0 d; MCategory: SAFE Developed by: ETF5( d5 {- S1 ?, o( t5 |+ x
OSM/LUM . @# O( u7 A: ]- a0 ZSubject:$ p# y R) h5 y h- ^
Short circuit and overload , v8 V/ I. F7 n6 N, V! j Wprotection9 h: O# f5 }! R' D9 U( E. T
Key words:! |: ~9 w6 ?# Q
- Transformers+ R+ ]- _+ I1 V
- Steady state conditions3 c; C/ [" J) }' d+ s) H
- Short circuit : f. M- ~( a$ B) K b0 {% oTo be approved at the 49th - W9 c/ I( F1 H/ ~+ ?CTL Plenary Meeting, in 20128 P$ g( m3 t1 w
Question: & o$ r" ^3 [) i- K4 E4 j& \Inherently short-circuit proof transformers shall be tested by short-circuiting the output windings until 9 _7 z B5 x' `( L7 ]0 s0 Osteady-state conditions are reached.: O* C- }5 e; z& s( B
In the IEC 61558-1 “steady-state condition” is not explained. Referring to other standards for the meaning0 |. ^0 W3 G# E# l) b& }' [
of “steady-state conditions”. Or “thermal stability”. The thermal stability is the change of temperature of' G' R3 y7 d0 }9 _+ D1 c6 f7 X
less than 1°C per hour. So the following questions arise: , R6 C$ U, N) O, OIs it correct to record the temperatures after one hour when temperatures didn’t change (more than 1°C/h)?5 v6 Z: A1 J5 z& e) \/ S3 `
How shall an inherently short-circuit proof transformer be assessed when the above mentioned( c0 R2 M, t0 n; n9 O; j, r" R
requirements are fulfilled, but the transformer is damaged 6h, after reaching the steady state condition, in6 g% E. A$ g ^3 s1 V
a way where safety will be impaired (the transformer bursts). 6 w1 j, B. J- G- d* uDecision: : ^( w6 o8 Y: S9 o* PYes. The transformer should not be accepted because the insulated materials are not corresponding to the " J$ K* ~8 W. e4 M! f# kinsulation class of the transformer.7 ^1 Z- j" O! }* ^4 i2 e
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PDSH 1021& ~2 L- P! n8 o# R