A balanced 3-phase-4-wire electric power supply is given with constant and equal line voltages be tween any two phases a

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A balanced 3-phase-4-wire electric power supply is given with
constant and equal line voltages be tween any two phases and
constant and equal line currents on all three phases.
Mathematically show that there is no current on the neutral wire if
current harmonics do not exist. Estimate the neutral current if 3rd
harmonic currents exist on all three phases with a magnitude equal
to 1/5 of the fundamental currents and the phase current = 100 A on
each phase. Besides that, there is no other harmonic current.