US-12620852-B2 - Rotor for rotary electric machine, manufacturing method and corresponding rotary electric machines

US12620852B2US 12620852 B2US12620852 B2US 12620852B2US-12620852-B2

Abstract

The present invention relates to a rotor ( 100 ) for a rotary electric machine, in which each package of plates ( 300 ) of the rotor ( 100 ) comprises, at both ends or end sections thereof, at least one first inverted plate ( 311 ) and at least one last inverted plate ( 312 ), said plates being inverted in relation to the other plates ( 310 ) of the package of plates ( 300 ).

Inventors

Jacques Roberth Ruthes

Assignees

Weg Equipamentos Elétricos S.a.

Dates

Publication Date: 20260505
Application Date: 20201211

Claims (8)

1 . A rotor for rotary electric machine, comprising: a package of plates, wherein each package of plates of the rotor comprises, at both ends or end sections thereof, at least one first inverted plate and at least one last inverted plate, said plates being inverted in relation to other plates of the package of plates; wherein the at least one first inverted plate and the at least one last inverted plate are positioned so as to physically cover and seal channels formed by upper holes of the other plates to prevent any conductive material injected into lower holes from migrating into the upper holes during manufacturing; wherein the upper holes of the other plates are arranged in an off-centered, offset or mirrored manner relative to a central radial shaft of the lower holes, such that the lower holes remain aligned throughout the package of plates; and wherein the upper holes are filled with an insulating material, and the lower holes are filled with a conductive material.
2 . The rotor according to claim 1 , characterized in that the at least one first inverted plate and the at least one last inverted plate are identical to the other plates, differing only by their inverted orientation within the package of plates.
3 . The rotor according to claim 1 , characterized in that the at least one first inverted plate and the at least one last inverted plate can be arranged, alone or together with one or more of the other plates, at ends or end sections of the same package of plates, serving as physical restrictors for the channels formed by the upper holes at such positions.
4 . The rotor according to claim 1 , characterized in that the package of plates can have more than one inverted plate at each end or end section thereof.
5 . The rotor according to claim 1 , wherein the insulating material is air and the conductive material is selected from aluminum or an alloy thereof.
6 . A method of manufacturing a rotor of claim 1 , the method comprising: i. stamping the plates with a central hole, lower holes and upper holes; ii. grouping and concurrently aligning a plurality of plates with the holes aligned with each other forming at least one package of plates; iii. arranging one or more inverted plates in each end or end section of the package of plates, inverted or mirrored in relation to the other plates; iv. arranging the package of plates to allow filling the channels formed by aligning the lower holes of the lower cage; v. injecting injectable material to fill the channels formed by the lower holes; and vi. pressing the shaft into one or more package of plates by inserting the shaft through the center hole.
7 . A rotary electric machine manufactured by the method of claim 6 .
8 . A rotary electric machine comprising a rotor of claim 1 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This patent application is a 35 U.S.C. § 371 National Stage filing of International Application No. PCT/BR2020/050539, filed on Dec. 11, 2020, the disclosure of which is incorporated herein by reference in its entireties. FIELD OF APPLICATION The present invention pertains to the field of rotary electric machines, including manufacturing and assembly methods thereof, in particular variable frequency asynchronous induction electric machines, notably electric machines equipped with rotors with short-circuited coils and with one or more cages. BACKGROUND OF THE INVENTION Rotary electric machines or simply electric motors are equipment used to transform electric energy into mechanical energy, in the case of motors, and vice versa, in the case of generators. They consist of essentially four basic structures, which are the housing, stator, rotor, and bearings/caps. The housing is the element responsible for integrating the other structures, encasing the stator and rotor. The stator is the static active (energized) component responsible for conducting the magnetic flow to rotate the rotor, in the case of motors, and conducting the energy generated by the rotor, in the case of generators, while the rotor is the active (energized) rotary component of the rotary electric machine. The bearings and caps are the elements responsible for coupling the static parts to the rotary parts of a rotary electric machine. In addition to these elements, depending on the distinct features of each rotary electric machine, there may be auxiliary systems such as excitation, cooling, lubrication, among others. The rotor, on the other hand, is basically composed of a shaft onto which a package of sheet or plates fixed together is arranged to form a package of plates that is sufficiently structured to withstand the use conditions of a motor, such as centrifugal force, temperature and others features which can influence and compromise the dimensional stability of the rotor set. The rotors of the motors addressed herein have through holes or openings or longitudinal grooves formed in the package of plates itself and parallel to the rotor shaft, in which each radially equidistant hole set, when filled with conductive material (forming bars) and having the ends joined by conductive material (short-circuit ring), form a cage, the same rotor can have one or more cages. Double-cage rotors basically have a cage closer to the motor shaft or lower and one closer to the outer surface of the package of plates or higher, in which the outer cage takes advantage of the skin effect to improve start performance, at which point the frequency of the currents in the rotor bars is equal to or close to the frequency of the supply line. Induction rotary electric machines can be powered by frequency converters producing a three-phase voltage system of variable frequency and amplitude, and the start of the electric machine controlled by a frequency converter does not imply a large start current. Instead, the stator frequency is reduced to a value close to the nominal slip frequency and the voltage amplitude is determined to produce the nominal flux. As such, obtaining the necessary start torque does not demand stator currents greater than the nominal current. Therefore, given that frequency-controlled induction electric machines are not exposed to the nominal voltage in the start condition, they do not need to have their leakage inductance increased, as limiting the starting current is not necessary. They can therefore be equipped with single cage rotors with open holes, which result in a smaller leakage flux, lower leakage inductance, and higher maximum torque value. However, due to the number of holes in magnetic circuits being constructively limited and the non-sinusoidal field distribution in conductors, the windings of an induction machine contain electromotive forces with higher order harmonics. In addition to said harmonics, there are also those imposed onto the motor by the supply voltage generated by the frequency converter. Said harmonics cause electric currents with equal frequency and the amplitude of said currents in the rotor is directly proportional to the amplitudes of the electromotive force frequency component and inversely proportional to the winding impedance. Note that the winding impedance at higher frequencies is predominantly determined by the leakage reactance. This is why reducing the leakage inductance causes an increase in current amplitude in the windings caused by the harmonics, fundamental and higher order, increasing current ripple and thus Joule losses in the windings. The adverse effects of high frequency losses can be avoided by using double cages with different materials, shaping the magnetic circuits of the stator and rotor, so as to reduce the electromotive forces induced by the distortions of higher order harmonics. One possible solution is using a single-cage rotor, in which the lower