Rotating Fields: Creation and Effects on the Machine Features

Abstract

The principle of operation of AC machines lies on the rotating field concept. Basically, it consists in a flux density moving in the cylindrical trajectory of the air gap of AC rotating machines. This chapter deals with the formulation of the rotating fields that could be generated considering different techniques, such as: (i) moving a single phase winding linked to the rotor and fed by a DC current (case of the field of the synchronous machines), and (ii) feeding a poly-phase winding by poly-phase sinusoidal currents. Then, the effects of the rotating field on the winding located in the vicinity, on the other side of the air gap, are analyzed. These effects are initiated by the induction of back-EMFs that could lead to the circulation of poly-phase currents in the involved winding. Consequently, a second rotating field is generated which is synchronized with the initial one, resulting in the production of an electromagnetic torque.