DSH 401 Mains supply transformers: Short Circuit and Overload tests

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Mains supply transformers: Short Circuit and Overload tests & E  m- u0 D. |- @

57.9.1

60601-1(ed.2);am1;am2 ) g! A: H+ G% p! Z

" q5 v% r) ]5 K4 U/ _. zStandard(s)- (year and edition):
IEC 60601-1:1988 Ed.2 Am1+Am2
& k* T' e2 G4 ^8 ?0 FSub clause(s): 57.9.1
  x1 n8 c. t. p4 vSheet n°: DSH-401
Subject: Mains supply transformers: Short Circuit and Overload tests
5 W; G4 H) e& {: N7 _Key words: Over-current, protection, overload
Confirmed by CTL at its 39th meeting, in Cologne
Question:
/ R( V. [- Y, f  q: n9 @; f6 l1 H8 kSecondary circuit OVER-CURRENT PROTECTION is the first active component on the
" X6 }. }) s3 n0 `% }4 ?" Zsecondary side of a mains supply transformer. Is the overload test performed before or after the
6 c! y# b" R8 t" L" f' Pfuse?
  p5 |; \6 G3 K6 Q, vInsufficient transformer winding crossover insulation and secondary circuit CREEPAGE
0 k3 c2 z* @; I4 n" T0 RDISTANCES and AIR CLEARANCES causes transformer winding to short-circuit and exceed
6 p+ ?1 W* M0 I3 G& gallowable temperatures.
Decision:
, Q" n. `" ?  h; l2 H# LIf the possibility of a short-circuit exists before the secondary OVER-CURRENT PROTECTION
2 p' d2 I3 s: F: z' Xdevice (e.g. failure of basic insulation between winding or detachment of the wiring) the short
circuit test should be conducted at the exit of the wiring from the transformer.
# R0 ^: \" K5 Q9 G(N.B. Similar recommendations can be made for batteries and their protective devices)
! U! X8 b, n& N! d# J9 p9 SThe overload test however must always be conducted after any secondary OVER-CURRENT
3 n- }4 v/ b. I9 Y7 ZPROTECTION device (conform clause 57.9.1b) providing that the conditions of sub-clause
57.9.1. second dash are fulfilled.

& `! T; l: K/ R