Asynchronous rotating machines comprise a stator with an ideally three-phase winding, and a rotor carrying either a cage winding or a multiphase coil winding. Usually the stator device is that the primary member, whereas the rotor is that the secondary member. Induction machine is that the term for Associate in nursing asynchronous machine provided solely within the primary half. Cage induction machines prevail in industrial electrical drives. Pole combine numbers P of 2,4,6 and generally eight square measure in use, with a preference for p = a pair of thanks to benefits in producing and specific price.
Wound rotor asynchronous machines feature slip-rings and brushes, permitting to feed the rotor winding. This can be the case with the doubly-fed asynchronous machines, typically used as WEG generators.
Figure above depicts a circuit diagram of a three-phase induction machine with star connected stator winding, the terminals U, V, W provided from the lines L1, L2, L3 of a three-phase grid. The rotor is additionally shown with a three-phase winding, the terminals K, L, M connected to slip-rings, the rotor circuit accessible by means that of slip-rings and brushes. Once the rotor-side is short-circuited the machine is comparable to a cage induction machine. For modeling functions the cage rotor winding may be transformed into a three-phase winding as shown. Note but, that for cage windings the properties relating to current displacement square measure totally different from actual wound rotors, thanks to the rotor conductor cross section pure mathematics.
Power conversion in asynchronous machines happens by means that of magnetic flux coupling the members via the air-gap. Its elementary element is rotating with synchronous speed spoken stator frame, with rotor speeds asynchronous to the main field, the rotor induced e.m.f. is of slip frequency (causing currents of identical frequency) and a force is created.
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