DSH 709/06 Short circuit and overload protection

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广东安规检测
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DSH 709/06 3 O9 M4 Y. p6 C' @* b

Short circuit and overload protection

15.2

61558-1(ed.2)

2 I9 l7 R* S% p3 s+ r! E) D# eStandard(s): IEC 61558-1/2005 No. Year
DSH
0709
; o% ^4 g; e9 q- z, `' V2008
Category: SAFE
Subclause(s): 15.2
" }( @; f1 D, lDeveloped by: ETF5
; [9 C/ c, i/ kOSM/LUM
Subject: Short circuit and
overload protection
: J$ p4 f& ?+ wKey words:
" `* D2 p2 y2 ?7 h/ e0 V- Transformers
2 @/ \: V  s! h) m6 T. [9 m2 q- Steady state conditions
- Short circuit
Decision approved at the
46th CTL Plenary Meeting,
in 2009
Question:
Inherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
steady-state conditions are reached.
  M; g$ S0 n9 U$ M3 M0 QIn IEC 61558-1 “steady-state condition” is not explained. Referring to other standards the meaning of
9 v5 {0 Q3 V3 N; @0 w“steady-state conditions” or “thermal stability” is that the change of temperature is less than 1°C per hour.
So following questions arise:
1) Is it correct to record the temperatures after one hour when temperatures did not change (more
. D; H  H% o4 r: Wthan 1°C/h)?
2) How shall an inherently short-circuit proof transformer be assessed when the above mentioned
/ b9 l  y6 ]5 ?  J  ]$ I; r/ Prequirements are fulfilled, but it is damaged 6h after reaching the steady state condition in a way
. a" g; r, o' n% w+ @where safety will be impaired (the transformer bursts).
) a- v3 k1 H3 v/ T- L+ F( rDecision:
1) Yes.
2) The transformer should not be accepted.

! i& i& r! n% s+ G0 `