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 . _6 `, v8 J, a/ F6 b2 v. a

15.2

61558-1(ed.2) % A9 Z" m. _' b

Standard(s): IEC 61558-1/2005 No. Year
/ \4 e0 S$ ]/ PDSH
0709
2008
; O% \9 ~4 i. ECategory: SAFE
( t( e- i( B4 h5 ^& d- `# gSubclause(s): 15.2
! z& u1 [5 G/ `) p# Z/ Q8 jDeveloped by: ETF5
: p( m6 k* g/ _0 O+ a  qOSM/LUM
' c- [9 z( F  h1 n& {, ]Subject: Short circuit and
9 U# v( _( L. w9 }% _overload protection
Key words:
- R( O* s3 `4 b, q- Transformers
# @7 k; k; d% }, l% y/ u' v) C- Steady state conditions
9 ~0 \) a, F8 _  [- Short circuit
Decision approved at the
46th CTL Plenary Meeting,
in 2009
) G% I9 d* R/ o; [4 uQuestion:
Inherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
4 K$ u# n8 r5 t8 k- ~$ R. }steady-state conditions are reached.
In IEC 61558-1 “steady-state condition” is not explained. Referring to other standards the meaning of
- S, ^/ @0 `* u! Z/ x“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
4 W5 t/ O/ \- h2 ?4 y: H+ J8 wthan 1°C/h)?
2) How shall an inherently short-circuit proof transformer be assessed when the above mentioned
requirements are fulfilled, but it is damaged 6h after reaching the steady state condition in a way
% T  a: C! u/ \where safety will be impaired (the transformer bursts).
Decision:
# U. i+ t9 L1 `7 Y1) Yes.
( j9 I2 M* i, t3 c$ o: I2) The transformer should not be accepted.


6 u9 m9 ?1 d; E& @4 j: \- y5 s  A