DSH 401 Mains supply transformers: Short Circuit and Overload tests

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DSH 401 1 H  d/ \2 Y# s$ w4 U + H9 u0 r3 v  P% `/ s- v

Mains supply transformers: Short Circuit and Overload tests

57.9.1

60601-1(ed.2);am1;am2

; m+ O$ }& Z0 H: h3 UStandard(s)- (year and edition):
8 x. H0 U; ?$ ~IEC 60601-1:1988 Ed.2 Am1+Am2
9 G0 |+ O* [1 ?3 L9 cSub clause(s): 57.9.1
/ H: l- g! B4 t' c" y4 @Sheet n°: DSH-401
Subject: Mains supply transformers: Short Circuit and Overload tests
4 [) g$ R8 u! B) QKey words: Over-current, protection, overload
& L2 l9 u$ \0 a! r7 C( O" i  VConfirmed by CTL at its 39th meeting, in Cologne
Question:
Secondary circuit OVER-CURRENT PROTECTION is the first active component on the
secondary side of a mains supply transformer. Is the overload test performed before or after the
) S7 U9 O$ O- y) |- mfuse?
Insufficient transformer winding crossover insulation and secondary circuit CREEPAGE
+ r) K+ s" v* X" h4 B5 Q0 D9 q' rDISTANCES and AIR CLEARANCES causes transformer winding to short-circuit and exceed
allowable temperatures.
, G9 |) L5 T" m( gDecision:
2 V$ L: I/ K9 ]$ F7 N2 e/ D4 @. HIf the possibility of a short-circuit exists before the secondary OVER-CURRENT PROTECTION
device (e.g. failure of basic insulation between winding or detachment of the wiring) the short
; L8 u$ z7 g2 O& E* h# ocircuit test should be conducted at the exit of the wiring from the transformer.
+ q) z! _: g* y6 R(N.B. Similar recommendations can be made for batteries and their protective devices)
/ \0 S5 s5 ]$ vThe overload test however must always be conducted after any secondary OVER-CURRENT
! f& T1 a* T( S$ A* r( yPROTECTION device (conform clause 57.9.1b) providing that the conditions of sub-clause
57.9.1. second dash are fulfilled.

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