The preciseness of the Torque display is depends of:
1. ... the correct adjusted Motordatas (Parametergroup B3)
2. ... the Autotuning datas (basically flux current and rotor coefficient), they have to be similar together.
3. ... the slip of the machine (a little bit different from motor to motor)
4. ... the different warming of the motors.
5. ... if there is used a SFB (speed feed back) or not ( depend to the adjustingof feed-back ).
The torque which is transmitted through the air gap in the motor is calculated via flux multiplied by current (vector product).