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What are the probable causes of current unbalancing at input side of ATV71 Drive.

(1) Example: input current R=175, Y=215, B=216
To know, if the problem comes from the ATV71 or from the main supply; this can be done if you inverse R and Y and perform the measurement of current like you did. If the current   in R becomes equal to 215 and the current in Y is 175, it means that the problem comes from the main supply.
(2) The balance of the current depends on the supply characteristics:
(a)Voltage balancing:
 An unbalanced input current may be caused by an unbalanced main supply voltage. we say that the unbalance voltage do not exceed 1.8% of the nominal voltage.    Please check it.
(b) Impedance balancing.
(3) Perhaps other devices are unbalanced or connected between two phases or phases and neutral.
(4) The input phase unbalance may be caused by a too small power for the main transformer. The transformer must be 2 times minimum the power of the drive.
(5) Make confirm cable size is same for all 3 phases as impedance network can cause unbalance of phase input current.
(6) Please check that there should be no-capacitor bank (APFC) connected to the R-phase.
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