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| DSH 401. t% {; I3 W8 B6 `$ |% g
; M3 L0 _3 [2 i | Mains supply transformers: Short Circuit and Overload tests
- ?$ p% {! V6 t) b- Y | 57.9.1
) N$ u1 \( D% b6 x | 60601-1(ed.2);am1;am2- Q6 i; [5 g0 s$ D! y
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# @- C/ Q; B9 B/ q) r4 E: y6 N; CStandard(s)- (year and edition):
0 C, f% J- {2 a0 c3 M. D% C7 ]3 MIEC 60601-1:1988 Ed.2 Am1+Am2$ D2 o3 Y, i7 n& u$ u
Sub clause(s): 57.9.15 a7 u( j! @5 k q1 O6 Y
Sheet n°: DSH-401 / G' k( L4 L) Z; L, ^
Subject: Mains supply transformers: Short Circuit and Overload tests6 M) [; E. `" r
Key words: Over-current, protection, overload; N/ I( }" N J& v4 Y5 H3 J
Confirmed by CTL at its 39th meeting, in Cologne
- C7 n, |9 T5 y& c9 CQuestion:; g3 T2 H$ ], J
Secondary circuit OVER-CURRENT PROTECTION is the first active component on the
* G( {% n; @2 @secondary side of a mains supply transformer. Is the overload test performed before or after the& \" @0 Z2 K. I
fuse?, b. c& f. J/ c$ h$ k6 g2 {, i/ n
Insufficient transformer winding crossover insulation and secondary circuit CREEPAGE
2 k9 g/ x# R2 N8 W" d* [DISTANCES and AIR CLEARANCES causes transformer winding to short-circuit and exceed
$ B5 i T8 l( a9 `1 k! m( yallowable temperatures.
. ^1 {3 t$ k1 {% R8 Z3 z: V6 qDecision:
: N* M" i& T5 A6 R [# ~4 OIf the possibility of a short-circuit exists before the secondary OVER-CURRENT PROTECTION
3 f4 [$ ?4 D' s! K( jdevice (e.g. failure of basic insulation between winding or detachment of the wiring) the short
0 c& ~6 p) V: o' s$ i/ O0 n/ vcircuit test should be conducted at the exit of the wiring from the transformer.( E& D" ^ }) g% U$ m7 X$ L
(N.B. Similar recommendations can be made for batteries and their protective devices)9 c1 F6 ~" }- P
The overload test however must always be conducted after any secondary OVER-CURRENT1 ~1 T6 I. _ w( q! v
PROTECTION device (conform clause 57.9.1b) providing that the conditions of sub-clause
' }! Q/ _ U& l. Y& ^, p: Q57.9.1. second dash are fulfilled.
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