In many three phase motor applications (both 480V wye and 240V delta)I have noted voltage imbalances around 1% to 2% with corresponding current imbalances ranging from 18% to 22%. Normally, two legs are close to FLA while the third led is exceedingly high. When motor leads are switched (keeping the same motor direction) the high leg always stays with the imcoming power indicating the problem is not load related. In addition, when multiple motors are unsed on the same power system the high amp leg is common to all motors. The power quality engineers at three different local power companies have no explanation except that the current to voltage imbalance ratio is normally 10:1. My question is; what is the mathematical relationship leading to this excessive current imbalance and what can be done to mitigate its effects short of derating the motors? Will checking power with a three phase power quality analyzer yield any answers?