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

Short circuit and overload protection

15.2

61558-1(ed.2) % S- ]) x4 U2 `! Y

5 v1 K2 G, q6 z! A# a" F, G3 UStandard(s): IEC 61558-1/2005 No. Year
DSH
0709
2008
9 Z4 o$ o# {% n+ H5 WCategory: SAFE
8 T! Y' u0 S- [6 [Subclause(s): 15.2
+ _; U' k, D" v2 nDeveloped by: ETF5
& Z0 {% j: }4 C, G) IOSM/LUM
Subject: Short circuit and
" }/ R, X" j; D7 a2 Q" z# h: ~( ]) Q( z1 Toverload protection
Key words:
( ]0 T* V) h* [  Y% e- Transformers
! x/ G+ r$ O7 ]) l+ ^- Steady state conditions
% _1 b2 D! J! }! c) K- Short circuit
1 ]) C/ C2 E9 }( U4 I) sDecision approved at the
46th CTL Plenary Meeting,
  ?' V* f" X$ w) ~in 2009
; ]! o& p$ N3 u  L  d4 ]  DQuestion:
Inherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
& g, T& [2 p# c) d) |" esteady-state conditions are reached.
- q$ @" @! o/ j) I+ e3 ^In IEC 61558-1 “steady-state condition” is not explained. Referring to other standards the meaning of
“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
6 R9 t+ e6 y8 Gthan 1°C/h)?
2) How shall an inherently short-circuit proof transformer be assessed when the above mentioned
- ?) k% r% z! b4 y" [! Q/ P1 X( Trequirements are fulfilled, but it is damaged 6h after reaching the steady state condition in a way
where safety will be impaired (the transformer bursts).
Decision:
1) Yes.
: ^' E! J4 {, N# P8 v2) The transformer should not be accepted.

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