I am using two Sinamic DCM drives for an Uncoiler Application in which there is 400 Amp armature drive and 40 Amp Field Drive ( Armature circuit used as a field Circuit ) is used . Both are in Peer to peer Communication . Both were running well for past 1 month . We are running the motor in Field Weakening Mode too . 

But the last night , There was a Flash in the Armature Drive in which all the armature side incoming Fuses ie 450 Amps for all the Phases were gone along with the 2 no of thyristors , pulse relay for the respective thyristors and Semi convertor circuit  for the Field Card .

One MCB ie 2 AC , 400 V for 3U1 and 3 W1  of Field found Burnt .

I am unable to find the cause for this extreme damage .

Can anybody help me on this matter ? 

One Doubt : If the Field Setpoint for the Field Drive becomed Zero in Running mode which is coming from the Armature Drive , What will be the outcome ? Can it bring the damages which happened with me .

Thanks .

I will be really thankful for the Help / Advice .

Sarabjot Singh Manku