DSH 401 Mains supply transformers: Short Circuit and Overload tests

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DSH 401 + b' i! {% O: N; E- c% f0 Z

Mains supply transformers: Short Circuit and Overload tests # z; r: s2 V& x- k5 [8 T* g5 X

57.9.1 : k, {2 P# l% K, M) m

60601-1(ed.2);am1;am2 6 l0 k% R3 O( @$ `$ T* O: r" ]

# B* M& J- p% Z' b4 O8 x6 w. kStandard(s)- (year and edition):
IEC 60601-1:1988 Ed.2 Am1+Am2
Sub clause(s): 57.9.1
Sheet n°: DSH-401
* {* N/ ^% v4 u* mSubject: Mains supply transformers: Short Circuit and Overload tests
9 ?1 _4 @/ O! `! UKey words: Over-current, protection, overload
, ~1 ?4 V& R' sConfirmed by CTL at its 39th meeting, in Cologne
Question:
Secondary circuit OVER-CURRENT PROTECTION is the first active component on the
$ A' h( A  l0 ]. \; V/ n+ Tsecondary side of a mains supply transformer. Is the overload test performed before or after the
9 A0 C: r  a5 T3 Vfuse?
6 k7 I* K" r" k3 P* \/ k. ^Insufficient transformer winding crossover insulation and secondary circuit CREEPAGE
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
device (e.g. failure of basic insulation between winding or detachment of the wiring) the short
8 Z4 E- k0 }6 B4 z) k2 Hcircuit 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)
9 _+ ^1 H" q1 }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
/ a3 d8 v) b. a/ B57.9.1. second dash are fulfilled.
8 q" T( ]/ e5 g3 o: K1 G

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