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55v - 110v centre tap transformer short circuit calculations

Anthony Sullivan

hello

i have been trying to work out how to work short circuit calculations for 110v systems. do i use 55V with c max or do use 110v or even use a 3phase calculation. i am trying to work out if a circuit will trip on 16A c type mcb for short circuit as i am putting a rcbo in to cover the fault current. 

110v 55v 

0.85ohms line to line tested

4mm 2 core cable 

 

Parents
  • 0

    Why 4.0 mm two core cable? the transformers and sockets where updated some years ago and the guy here just reused the cable. 

    What is the output rating of the transformer? not to sure. probably a 5kva 

    Does the transformer already have fuses in it on the output? the transfomer has two outgoing ways 16a c double pole. 

    fixed installation

    i got .25ohms on the z at tx and .85zs at the furthest socket. the short circuit on the multimeter had a result of 142a and around 70a down to earth. the results line up with the calculation. so line to line calculation need 110v and line to earth 55v. makes scene. i just saw a calculation of phase to phase short circuit and wanted to check if that was used 

    thanks guys

Reply
  • 0

    Why 4.0 mm two core cable? the transformers and sockets where updated some years ago and the guy here just reused the cable. 

    What is the output rating of the transformer? not to sure. probably a 5kva 

    Does the transformer already have fuses in it on the output? the transfomer has two outgoing ways 16a c double pole. 

    fixed installation

    i got .25ohms on the z at tx and .85zs at the furthest socket. the short circuit on the multimeter had a result of 142a and around 70a down to earth. the results line up with the calculation. so line to line calculation need 110v and line to earth 55v. makes scene. i just saw a calculation of phase to phase short circuit and wanted to check if that was used 

    thanks guys

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