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The multifunctional asynchronous electrical machine

Domenii publicaţii > Stiinte ingineresti + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Vasile Tudor

Editorial: 2011.


The technical solution for electric operations refers to a multifunctional asynchronous electrical machine, capable of executing diverse movements, from rotation and translation, to compound movement of the helical type, which is especially used as an electric motor in the field of electric operations, but as an electromagnetic brake and even an electric generator. At the moment the asynchronous electric engine with a spinning magnetic field which, although has a simpler build than the synchro and allows to regulate the revolution, cannot execute other movements than rotation, which limits its range of uses. The technical solution proposed eliminates these disadvantages through the fact that the multifunctional electric asynchronous machine is fitted with an intermediary empty cylinder type impeller with both faces in short-circuit, disposed coaxial between the exterior stator (on which there are the polyphased winding for the spinning magnetic field) and interior stator (on which there are the polyphased winding that assures a progressive magnetic field of longitudinal translation on the direction of the succession of the phases). Further is given an example of achieving the technical solution, which represents a section through a multifunctional electric asynchronous machine. The electric asynchronous machine prototype is mainly composed of an exterior stator 2, an interior stator 4 and an intermediary impeller 1, which are coaxially disposed. The exterior stator 2 and impeller 1 are of empty cylinder type, and the interior stator 4 is of a full cylinder shape. The spinning magnetic field is generated by the three-phase electric winding, arranged in the notches applied on the interior face of the stator 2, and the progressive translation magnetic field is produced by the 5 three-fazed winding, placed in the notches applied in the lateral surface of the 4 stator.
The intermediary rotor 1 has both faces in short circuit , squirrel cage type for the exterior face, an assembly of parallel and equidistant conductor rings for the interior face. The 3 and 5 three-phase winding (with the role of electric circuits) are made of copper wire isolated with varnish, and the 2 and 4 feromagnetics supports, which make up the magnetic circuits, as well as the 1 intermediary rotor are made of electrotechnical steel plate cold laminated and isolated with varnish, to reduce the losses through hysteresis effect and flow vortexes. From a structural and functional point of view, the multifunctional asynchronous machine is a combination of a rotating electric asynchronous machine (unit 1 and 2) and a new constructive variant of asynchronous machine with linear action (unit 1 and 4) coupled between them through a common mobile part. As for the engine, the multifunctional asynchronous machine assumes electric power from the charging network, which it transforms in mechanical power through the interaction forces between the magnetic fields produced by the three-phase currents from the constantly and the currents induced into the rotors conductors. Further on only the structure is being presented and the way the unit made of rotor 1 and stator 4 will work, because rotating asynchronous electric machines are well-known at the level of today’s technology, from specialty works for electric operations. The 5 three-phased winding is made of circular coils, placed parallel and equidistant on stator 4, in the notches applied on its lateral surface. The coils for every phase of the charging tension are made from coils joined in series and alternatively wrapped, in one way or another. The beginning extremities of the phase winder are tied separately at the exterior terminals A, B and C, and the ending extremities are tied together at the O null coil. The electrical charging from the three-phase network of alternative current can be made from a star fitting or a triangle fitting. The electric currents from the 5 three-phased winding can produce a progressive translation magnetic field on the longitudinal direction. The variable magnetic field made by the 5 three-phase winding induces in the conductive rings of the mobile part 1 alternative electromotive tensions in proportion with the variation speed of the magnetic flow through surfaces delimited by the rings. The magnetic fields inductor and induced, interact among themselves through electromagnetic forces whose resultant has a unnull longitudinal component, which assures the translation motion of the mobile part 1 of the multifunctional asynchronous machine. The rotation movement of the mobile part 1 is assured by the torque of the interaction forces rotating magnetic field made by the three-phase winding 3 and the magnetic field produced by the currents induced into the squirrel cage type electric circuit conductors. It’s easy to understand, on the basis of the law of electromagnetic induction and the principal of effect overlapping, the independent actions of the magnetic fields produced by the three-phase winding 3 and 5 on the faces in the short-circuit of the intermediary rotor. The whirling magnetic field produced by the three-phase winding 3 has the field lines arranged normally on the surfaces limited by the squirrel cage conductors in its vicinity, in which it induces intense electric currents. The interaction forces which brings forth the torque engine are perpendicular to the rotation axis, unlike the translation magnetic field produced by three-phase winding 5 (which induces intense electric currents only in the conductor rings of mobile part 1, their surfaces being mostly recrossed by field lines, the interaction forces have in this case a component parallel with the rotation axis, which assure the translation motion). In other words, the rotating magnetic field and the translation magnetic field, having perpendicular field lines, will act through perpendicular forces on the mobile part, which has the squirrel cage conductors on the planes normally arranged on the planes of the conductor rings. Through the make up of the translation motion with the rotation one we obtain a resulting motion of the mobile part 1 of helical type. Another constructive variant of the multifunctional electric machine is obtained through mutual changing winding positions 3 and 5, in which case the lateral exterior side of the mobile part 1 is fitted with conductor rings and the interior side is fitted with squirrel cage type electric circuit. Even the mobile part 1, with both sides in short-circuit, can be replaced with a rotor having fitted on the sides permanent magnets or feromagnetics pieces which assure a variable reluctance, their shape being adapted to the type of polyphased winding which it neighbours. To avoid electrical overcharges and mechanic shocks, the starting of the asynchronous engines with the rotor in short-circuit can be achieved by connecting directly to the network, only for small powers, and for powers bigger than 10kW, the starting is made through some autochanger, some star-triangle switches or some coils tied in series with three-phased statoric windings. Adjusting the revolution and the speed of the longitudinal displacement of the mobile part 1 can be made through the variation of the amplitude and frequency of the tensions applied to the winding coils 3 and 5, with the help of rheostats, respective of some frequency converters. The alternative motion of mobile part 4 can be obtained with the help of tripolar electric switches (to change the order of phase succession) or even through the usage of some stators which present symmetric sectors with inversion in the order of phase succession. For the production we can use a modified version of the asynchronous motor, in which the intermediary rotor 1 is fitted on both sides with squirrel cage type electric circuits, and stator 4 and coil 5 are replaced with a interior rotor on which a three-phase winding is placed for generating the second rotating field. In this case, the global effect is cumulative if the two rotating fields determine the same motion direction as the interior rotor. Multifunctional asynchronous electric machines are reversible, the rotation and translation speed (also known as synchronism speed) of the rotating magnetic field respective progressive, represent limit values for the proceeding from the motor system to the electric generator system and vice versa. As for the engine, the rotation and translation speed of the mobile part 1 are less than the corresponding synchronism speed, and by overlapping of this limit values it shifts to the electric generator system. Hindering asynchronous motors can be realized, not only through shifting to generator system with energy recovery, when induced currents create a resistant torque, but also through reversed connection or even through continuous current injection. There are different variants for asynchronous electric machines which differ through the number of fazes and the manner of arranging of the electric circuits, as well as through the dimensions and the nature of the materials from which the components are made of. It is easy to imagine a multifunctional electric motor of a step by step type. Multifunctional asynchronous motors are especially useful in robotics, and generally in automatization, as elements of executions in automatic regulation systems. By associating with processing computers, we can accomplish automatic systems which can carry out complex functions.

Cuvinte cheie: Ad Astra