Damage check points of Thyristor (SCR) or Quick fuse
Check protection system connection, contact is good or not.
During protection action check, the conduction angle of rectifier can drive into inverting condition 120°<α<150°.
Check smoothing reactor, wire has breakdown short circuit or not.
Check thyristor RC-snubbers circuit is good or not, any loose or dropping on connection.
Check main power circuit fastener has any loose or not.
Check load system has open path or not.
Check inverter has three-leg running or not, rectifier has lack phase running or not (sm
oothing reactor has abnormal shock noise).
Check main power ground insulation condition.