Efficiency is the ratio of (Drive power) and (Drive power + losses)
The losses are giving in Altivar 12 catalog ( Refer the attached file )
Example for ATV12HU22M2
Example for ATV12HU22M2
Power=2.2 Kw
Losses=93W
Efficiency (at 100% of load) = (2200)/ (2200+93) =95.94%