DSH 401 Mains supply transformers: Short Circuit and Overload tests

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DSH 401 5 l, K1 |4 P, V6 y* {6 C + g% T$ C+ G. j5 f. I& X; M( m$ T

Mains supply transformers: Short Circuit and Overload tests # o9 y! H3 x) i* ~1 z

57.9.1 ) C& f& V& }- x: |

60601-1(ed.2);am1;am2   @' E, R0 X0 F, x; ]0 [# N

* z$ j( P/ E9 ]# r$ S6 x: \Standard(s)- (year and edition):
) `% A  M1 ^( N/ t! NIEC 60601-1:1988 Ed.2 Am1+Am2
, \6 S- u9 U, ~% ?Sub clause(s): 57.9.1
% b: {% x( P6 u7 b& xSheet n°: DSH-401
Subject: Mains supply transformers: Short Circuit and Overload tests
Key words: Over-current, protection, overload
- x1 W  w' S- Y9 p1 j/ T0 B9 @Confirmed by CTL at its 39th meeting, in Cologne
. w3 x7 M- V# UQuestion:
2 P0 R) \- u: e* T7 s' pSecondary 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
fuse?
Insufficient transformer winding crossover insulation and secondary circuit CREEPAGE
/ @& u+ a# p; [2 C" h  \DISTANCES and AIR CLEARANCES causes transformer winding to short-circuit and exceed
allowable temperatures.
Decision:
If the possibility of a short-circuit exists before the secondary OVER-CURRENT PROTECTION
  B# d: s1 U" P: E* ]device (e.g. failure of basic insulation between winding or detachment of the wiring) the short
# q& u2 I' B$ Q6 B; ^9 Dcircuit test should be conducted at the exit of the wiring from the transformer.
(N.B. Similar recommendations can be made for batteries and their protective devices)
The overload test however must always be conducted after any secondary OVER-CURRENT
PROTECTION device (conform clause 57.9.1b) providing that the conditions of sub-clause
57.9.1. second dash are fulfilled.
) b. D. a8 A3 {- c7 V& I