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|  DSH 401
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| Mains supply transformers: Short Circuit and Overload tests" @8 k% Y1 R* B, F, U5 P
| 57.9.1
7 _* m0 `& Y) o" R& U# k | 60601-1(ed.2);am1;am2
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Standard(s)- (year and edition):2 E* L% }, _8 {
IEC 60601-1:1988 Ed.2 Am1+Am2
$ s6 y: T3 P9 V' w1 n% l: ]9 ESub clause(s): 57.9.1: A" Q* P2 h4 q' [' p% t) \2 J8 O1 W& T
Sheet n°: DSH-401 1 V, y9 {1 ^: ]: t
Subject: Mains supply transformers: Short Circuit and Overload tests( N7 a5 Z! O9 {. _( L/ ?
Key words: Over-current, protection, overload8 z1 `* z1 }) g2 i+ W4 @
Confirmed by CTL at its 39th meeting, in Cologne% A$ \4 D) d( i3 u1 T
Question:! p6 {2 ~; K" y1 h5 C+ q: D
Secondary circuit OVER-CURRENT PROTECTION is the first active component on the
1 u, C0 U: S9 Asecondary side of a mains supply transformer. Is the overload test performed before or after the
- @' Y% J4 Q8 d+ O" ]fuse?7 X D2 L1 {2 r3 J( p. w
Insufficient transformer winding crossover insulation and secondary circuit CREEPAGE0 b8 Y3 E5 n+ }5 Q n
DISTANCES and AIR CLEARANCES causes transformer winding to short-circuit and exceed5 i6 J. X5 o/ q& R. l _ V' f
allowable temperatures.
# m% `' j3 m4 t: G$ m& E" vDecision:1 t! n- k3 O! u+ E; ^
If the possibility of a short-circuit exists before the secondary OVER-CURRENT PROTECTION
& h) ], r8 G/ |# V. j& \device (e.g. failure of basic insulation between winding or detachment of the wiring) the short& H# p7 w+ j: X+ D- ^
circuit test should be conducted at the exit of the wiring from the transformer.- ]) T5 U( D" }2 c+ y/ b: r* A
(N.B. Similar recommendations can be made for batteries and their protective devices)% l; U% Q4 |# W7 O4 Z1 G/ ^6 P
The overload test however must always be conducted after any secondary OVER-CURRENT0 @# J! O' R A# I4 V
PROTECTION device (conform clause 57.9.1b) providing that the conditions of sub-clause- L: U* V$ B; L$ d$ X
57.9.1. second dash are fulfilled.6 A- x! R |! E' C- s) j* [
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