Rotating Magnetic Field from Single Phase CurrentSingle phase current passing through a coil will produce a fluctuating magnetic field.
|Fig.1 Fluctuating magnetic field produced by a single phase current|
|Fig.2 In secondary winding magnetic flux will fluctuate perpendicular to first winding flux|
|Fig.3 A capacitor in secondary winding will make sure that the fluctuating fluxes are in 90 degree phase difference|
Variation of Resultant Magnetic Field with TimeResultant magnetic field is sum of these two fields. Now note the variation of resultant magnetic field with time.
|Fig.4 Resultant is sum of 2 fluctuating fields, this is same as rotating magnetic field|
|Fig.5 Magnetic field rotates in the direction of arrow|
Different Number of PolesWinding in Fig.5 produced 2 poles. In actual machines there could be many poles, so that synchronous speed can be varied. Following figure shows a 4 pole magnetic field.
|Fig.6 A 4 pole rotating magnetic field|