Harmonics effect on rectifier current imbalance

Analyzed data collected during the field test of close coupled 12 pulse rectifier-transformer with wye and delta bridges connected in parallel. Observed the wye delta current imbalance higher then expected based on transformer data. Found the substantial presence of 5^th harmonic in the incoming line voltage. Provided explanation of measured difference between the wye delta voltages due to harmonics presence. Presented the effect of harmonics on the rectifier current imbalance. Calculated current imbalance based on the observed harmonic content and transformer during the tests.