General guide to the selection of DIN Fuse Links for use in the primary circuit of three phase transformers
1. The fuse link should withstand transformer magnetising inrush
currents, taken as 12 times full load current for 0.1 seconds.
2. The fuse link should discriminate with the rating of secondary
fuse link stated or where only individual cable exit protection
exists, the highest rating likely to be used.
3. The fuse link should operate within 2 seconds for transformers
complying with IEC60076 - 5 in respect of impedance, voltage
and short circuit withstand current.
4. The fuse link should operate reasonably quickly in the event of a
transformer internal fault, or an earth fault in the secondary
terminal zone of the transformer.
5. In the case where there is no secondary fuse link for overload
protection, the minimum recommended HV fuse link rating
applies to the use of fuse links in encapsulated enclosures where
permissible continuous overload is generally limited to 20% of
transformer full load current. However if greater overload currents
are permissible a higher rating of fuse link may be required.
Where the fuse link is used in open air or conditions of unrestricted
ventilation a higher permissible overload may be possible.
6. In most cases more than one rating of HV fuse link is recommended
for a particular transformer size. Choice of fuse link will then
depend on which fuse offers the best protection e.g. having one fuse
for several transformer sizes.
Recommendations for other voltages are available on request.
For HV DIN Fuse Links type SXLSJ, SDLSJ, SFLSJ, SKLSJ, SDMSJ, SFMSJ, SXMSJ SDQSJ, SFQSJ. Selection guide
using LV Fuse Links operating class gG/gL on the low voltage side for overload protection of the transformer.
Selection of these HV fuse links has been based on the following:
For HV DIN Fuse Links type SXLSJ, SDLSJ, SFLSJ, SKLSJ, SDMSJ, SFMSJ, SXMSJ SDQSJ, SFQSJ. Selection guide
using LV Fuse Links operating class gG/gL on low voltage side for individual cable exit protection.
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Selection Table for Back-up Fuse LinksSelection Table for Back-up Fuse Links