Is it possible to determine the KW of AC induction motor without checking the nameplate
KW = power factor* line voltage * full load current *
1.7321( if it’s a 3 phase motor)
Use a strobe tachometer to determine motor RPM and then set up a generic motor in the database for that RPM. If loading cannot be provided by the operator use the acquired data and RPM to approximate loading. You can view the power factor for a value around .88 to .92 to approximate the full load. you can just run the motor for three minutes while clap on one phase, the current reading and the supply voltage with the square root of three will give you approximately the Rating of your equipment.
To determine the HP run your motor at full load, use your clamp meter to know the full load current. Then apply the formula √3vi*pf in the case of a 3phase motor