A three-phase induction motor usually has no neutral because its three-phase windings are connected in star (Y) or delta (Δ) and the currents are balanced.
In a balanced three-phase system: IA + IB + IC = 0
Therefore, no neutral conductor is needed to provide a return path.
Power is supplied through the three phase wires (R, Y, B).
The motor’s earth/ground wire is for safety, not for carrying normal current.
So, a normal 3-phase motor can operate with 3 phase wires + earth, without neutral.
In a single-phase circuit, neutral is normally needed because it provides the return path for current.
For example:
Phase → Load (fan/bulb) → Neutral → supply
Current flows from the phase wire through the appliance and returns through the neutral wire.
Why 3-phase is different
In a balanced 3-phase motor, the three phase currents are displaced by 120° and their sum is zero:
IR + IY + IB = 0
So the currents effectively return through the other phase conductors, and a separate neutral isn't required.