Calculating phase currents and neutral phase current
No guarantees as to correctness, but this shows the general method.


Find the real and reactive power flowing in each phase.
Determine the current flowing in each phase, including the angle between phase current and phase voltage.
Add all currents vectorially - real and imaginary components. A diagram helps.


By convention, phase rotation is anti-clockwise. An inductive load will make the current lag behind the voltage. (Remember, inductors resist changes in voltage dv/dt.)

Diagrams below are not to scale.