The “motor current” is the amplitude of the motor phase currents while the “phase current” represents the current measured on each of the motor phases.
The picture below shows the motor current and the phase currents in case of a brushless motor, driven in sinusoidal mode.

With red line is the current on the A phase (IA), with yellow, the current on the B phase (IB), with blue, the current on the C phase (IC) and with white, the motor current (IQ).
The motor current (IQ) is always the amplitude of the currents on each phase.

The motor current is computed using the relation below:

IQ = [IA*(1/sqrt(3)) + IB*(2/sqrt(3))]*cos(theta) – IA*sin(theta)

where:
– IA and IB are the phase currents (IC is considered to be IC = – IA –  IB)
– IQ is the motor current;
– theta is the electric angle.