Sunday, 7 July 2013

Sinusoidally distributed windings and fields in a 3-phase ac machine


The stator of a 3-phase (2-pole) AC machine may be represented by 3 sinusoidally distributed windings [RGB] whose axes are displaced by 120o. When the windings are excited with balanced 3-phase sinusoidal currents, each phase produces a pulsating sinusoidal field described by a space vector directed along the winding axis and pointing to where the field is maximum positive. The combined effect is equivalent to having a single sinusoidally distributed winding which is excited with a constant current and rotates at the excitation frequency. The motion of the associated space vectors is illustrated.

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