its very simple first note the current rating of the motor on the name plate then adjust the current setting just above the name plate motor of the motor

It depends on a lot of factors like current density for mm^2 temperature is the cable on cable trays or buried or inclosed in PVC is that a 3 phase cable multicore or what and also depends on the voltage but in general making a current density 2 A/mm^2 for copper for simple applications is good.

First we calculate the amp rating of the equipment.for cu we take 2.5A & for alu we take 1.5 to 1.7A for 1sqmm cable.