The production of Rotating magnetic field in 3 phase supply is very interesting.

When a 3-phase winding is energized from a 3-phase supply, a rotating magnetic field is produced. This field is such that its poles do no remain in a fixed position on the stator but go on shifting their positions around the stator. For this reason, it is called a rotating field.

It can be shown that the magnitude of this rotating field is constant and is equal to **1.5 **fm where fm is the maximum flux due to any phase.

The three-phase currents flow simultaneously through the windings and are displaced from each other by 120° electrical. Each alternating phase current produces its own flux which is sinusoidal.

So all three fluxes are sinusoidal and are separated from each other by 120°.

If the phase sequence of the windings is R-Y-B, then mathematical equations for the instantaneous values of the three fluxes Φ_{R , }Φ_{Y ,}Φ_{B} can be written as,

_{R }= Φmsin(ωt)

_{Y }= Φmsin(ωt – 120)

_{B}

_{ }= Φmsin(ωt – 240)

### Case 1 : ωt = 0

_{R }= Φmsin(0) = 0

_{Y }= Φmsin(0 – 120) = -0.866 Φm

_{B}

_{ }= Φmsin(0 – 240) = +0.866 Φm

### Case 2 : ωt = 60

_{R }= Φmsin(60) = +0.866 Φm

_{Y }= Φmsin(- 60) = -0.866 Φm

_{B}

_{ }= Φmsin(- 180) = 0

### Case 3 : ωt = 120

_{R }= Φmsin(120) = +0.866 Φm

_{Y }= Φmsin(0) = 0

_{B}

_{ }= Φmsin(- 120) = -0.866 Φm

### Case 4 : ωt = 180

_{R }= Φmsin(180) = 0

_{Y }= Φmsin(60) = +.866 Φm

_{B}

_{ }= Φmsin(- 60) = -0.866 Φm

Anne says

Not sufficient content.please do explain. the direction of fields due to 3 windings.Thank you!

admin says

Thank you Anne for your suggestion. We will update the article shortly.