current measurement
3 phase motors will have the current in each phase pretty close to equal , if not, there will usually be a problem and eventually failuire due to overheat.
I am more familiar with 3 phase 400 volt motors and the rule of thumb I use is 2.2 amps /Kw/phase. With 220 volt 3phase the current will be approximately double that of 400 volt 3 phase.
Again, the motors I am familiar with will have only one phase measured. This method you use for depends on the type of ammeter you opt for.
It can be a direct reading ammeter in which case the current measured is taken through the ammeter, or in the indirect type the CT is matched to the ammeter and the current in the ammeter is a sample of that flowing in the supply to the motor.
Hope this helps.
JMcG