In this topic, you study Induction Motor – Definition & Diagram.
Induction motor operates with alternating current supplied directly to the stator winding and by induction, or transformer action, to the rotor winding. It is for this reason that motors of this type are known as induction motors. A pictorial Dismantled view of a 1-phase induction motor s
Fig. 1: Dismantled view of a 1-phase induction motor
In fact, an induction motor can be considered as a sort of rotating transformer i.e. one in which a stationary winding on stator is connected to the ac source, while the other winding mounted on a rotor receives its power by transformer action while it rotates. of all the types of ac motors, the three phase induction motor is by far the most common type.
Fig. 2: Three-phase induction motor
Essential Conditions to be satisfied for obtaining a rotating Magnetic Field. When the three phase windings displaced in space through 120 electrical degrees are supplied with the three phase currents having time phase difference of 120 electrical degrees, they produce a uniformly rotating magnetic field. Similarly, it can be shown that when a two-phase supply is applied across two phase windings displaced in space through 90 electrical degrees, a rotating magnetic field is produced. In general, following conditions should the satisfied for obtaining a rotating magnetic field:
- A polyphase supply must be available i.e. say 2-phase. 3-phase, etc.
- A polyphase winding across which a polyphase supply is being applied for obtaining the rotating magnetic field should have phases equal to number of supply phases.
- The various phases of the polyphase winding must be displaced from each other by an angular distance (in electrical degrees) in space equal to the electrical phase difference (with respect to time) between the currents supplied to them by the polyphase supply.