This Technical Report is published as an application guide that applies to semiconductor convertors with fuses for the protection of the semiconductors forming the principal arms of these convertors. It is limited to line commutated convertors in single-way and double-way connections, and to fuses satisfying the requirements of the IEC Publications 269-1 and 269-4, listed in clause 2. Where applicable, the general clauses of this report may also give guidance for other convertors covered by the IEC 146-1-1, IEC 411 and IEC 411-1, listed in clause 2. The object of this report is to advise on the specific fuse features and on the specific convertor features which are to be observed to ensure correct application of semiconductor fuses in convertors, and to give specific recommendations for trouble-free operation of convertors protected by fuses. In this report the most important guide lines are illustrated by means of the three-phase convertor connections with fuse protection of their principal arms. They are, however, also applicable to the connection of other convertors covered by IEC 146-1-1, IEC 411 and IEC 411-1, listed in clause 2.