DSH 401 Mains supply transformers: Short Circuit and Overload tests

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DSH 401 2 Z5 `6 k% i$ x" A

Mains supply transformers: Short Circuit and Overload tests 1 t5 A! d5 Q  \# u

57.9.1 . c$ w8 I' n3 N( Y9 [3 p

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

Standard(s)- (year and edition):
6 g( J# ~/ X) v- \! CIEC 60601-1:1988 Ed.2 Am1+Am2
+ ^& h( @6 _0 j$ q4 I* p  ]Sub clause(s): 57.9.1
Sheet n°: DSH-401
$ G" s; `* W8 u2 C1 `Subject: Mains supply transformers: Short Circuit and Overload tests
# _* p4 Q- v) [' }Key words: Over-current, protection, overload
! W1 N/ z6 P3 \' `, X) p) _Confirmed 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
fuse?
Insufficient transformer winding crossover insulation and secondary circuit CREEPAGE
* U8 }2 P6 g1 @' j4 YDISTANCES and AIR CLEARANCES causes transformer winding to short-circuit and exceed
allowable temperatures.
9 {& a) h3 O0 nDecision:
If the possibility of a short-circuit exists before the secondary OVER-CURRENT PROTECTION
( e+ T. S0 }# v: 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.
; s7 i9 e. M$ p# N  A% {# ]# Z(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.

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