Bus current represents total power through the DC link, while phase currents represent what each motor phase actually receives and what the FOC or torque controller needs to regulate. Ignoring inefficiencies, commutation and commutation details (see below), the product of "input voltage x input current" should be equal to the "output current x effective motor voltage". Moreover, electrical current can be measured with different sensor types. From this. BLDCs are fascinating because the phase currents make up a three-phase sine wave - essentially three sine waves, each 120° offset from eachother.