DE112021008063T5 - Air guide element for the coil head of rotors of rotating electrical machines and corresponding rotating electrical machine - Google Patents

Abstract

The present invention relates to an air guide element (100) for the coil head (200) of pole (300) rotors (400) of rotating electrical machines, which is arranged under the coil heads (200) in a position which is closest to the area with increased air supply (210) and is located substantially centrally or midway with respect to each of the poles (300). The present invention further relates to a corresponding rotating electrical machine.

Description

field of use

The present invention belongs to the field of rotating electrical machines, in particular synchronous machines with a solid pole rotor, in particular arrangements for air cooling or ventilation through channels in parts of the magnetic circuit or between conductors.

Background of the invention

Rotating electrical machines are devices that convert mechanical energy into electrical energy (generators) or electrical energy into mechanical energy (motors).

The rotors of turbo generators with four solid poles are usually self-ventilated and do not require additional fans for ventilation. In the rotor coil head, some components, such as the shaft fins and the rotor press ring, contribute to generating air flow in this area, although they are not able to better homogenize the air flowing through the exposed coils.

In conventional turbogenerators of typical power, this air flow and distribution condition is sufficient to cool the magnetic and conductive assembly and maintain temperatures at suitable and satisfactory levels for the expected thermal performance.

In high-performance turbogenerators, a commonly used solution to reduce mechanical losses and increase performance is to reduce the airflow through the rotor's radial channels and coil ends by creating a pressure drop, thereby reducing the friction between the rotor (and its components) and the air.

However, this solution significantly reduces the airflow cooling the coil heads of the solid pole rotor. This creates an uneven distribution of the airflow, causing some areas of the rotor coil head to receive a stronger airflow than others. This causes a thermal imbalance in this area and therefore an undesirable temperature increase in certain places of the coil head. In addition to the temperature increase in some hot spots, there is also an increase in the temperature difference between the less hot and the hotter spots due to poor heat exchange. This can lead to generator failures due to local overheating, create a short circuit between the turns and even cause undesirable movement of the winding.

Increasing the performance of rotating electrical machines of the type discussed here is at odds with the necessary heat exchange. Balancing performance and cooling is therefore a challenge and imposes limitations on turbogenerator manufacturers around the world that go beyond size and power constraints.

State of the art

In the state of the art, there are several solutions that describe ventilation or cooling systems for solid-pole rotor coil heads of rotating electrical machines of the type discussed here.

For example, the patent discloses and describes WO2020021673 entitled "ROTOR OF ROTATING ELECTRIC MACHINE", a rotor having a cylindrical retaining ring covering the end of the coil and open in the outer axial direction, and a rotor baffle and an insulating baffle circumferentially connected to each other to divide a space in the retaining ring into first and second spaces. The first space is formed along the entire circumference about an axis, and the rotor baffle is provided with a first tapered part tapering from a cross part toward the center side of the rotor in the axial direction at the position where the cross part is present on the outside of the rotor baffle in the radial direction.

Although the solution of WO2020021673 achieves an even direction of the air flow generated by the rotor, it relies on a set of rotor baffles, which also depend on insulating baffles. This solution nevertheless does not equalise the temperature distribution in the coil head due to the baffles because they are mounted in the areas between the poles and do not have openings for air entry. Instead, they are completely closed and direct the air to the air ducts in the rotor pack. The retaining ring limits heat exchange by keeping the coil head area closed. In addition, the air flow from this rotor is directed, among other things, in air paths cut into the rotor, i.e. it must be taken into account that the rotor is specifically built for this solution, which limits its versatility.

As can be seen from the above description, there is a need for a cooling solution for rotating solid-pole rotors of electrical machines that eliminates the disadvantages of the prior art, in particular especially for cooling the coil heads of solid pole rotors.

Objectives of the invention

One of the objects of the present invention is therefore to provide an air guide element for the coil head of rotors of rotating electrical machines according to the features of claim 1 of the appended claims.

Yet another object of the present invention is to provide a rotating electric machine according to the features of claim 12 of the appended claims.

Further features and their details are described by the dependent claims.

Short description of the characters

• 1: eine isometrische perspektivische Ansicht eines erfindungsgemäßen Luftleitelements;
• 2: eine Draufsicht auf den in 1 gezeigten Luftleitelement;
• 3: eine isometrische perspektivische Ansicht eines Rotors einer erfindungsgemäßen elektrischen Maschine;
• 4: eine teilweise Draufsicht der in 3 gezeigten elektrischen Maschine und die Position des Luftleitelements;
• 5: eine Seitenansicht eines Teilausschnitts des Rotors einer erfindungsgemäßen elektrischen Maschine;
• 6: eine vergrößerte Ansicht von in 5 gezeigten Detail A und die Position des Luftleitelements;
• 7: eine Vorderansicht des in 5 gezeigten Abschnitts B-B, die die Position des Luftleitelements zeigt; und
• 8: Diagramme von praktischen Tests, die die Temperaturverteilung im Rotor-Spulenkopf (oben im Diagramm) und die Luftgeschwindigkeitsverteilung in radialer Richtung am Lufteinlass des Spulenkopfes (unten im Diagramm) mit und ohne Luftleitelement gemäß der Erfindung darstellen.

In order to better illustrate the subject matter of the present invention, it will now be described with reference to the accompanying figures, which illustrate the technical effect achieved by an exemplary embodiment without limiting the scope of the present invention. They show schematically:

• 1 : an isometric perspective view of an air guiding element according to the invention;
• 2 : a top view of the 1 shown air guide element;
• 3 : an isometric perspective view of a rotor of an electrical machine according to the invention;
• 4 : a partial plan view of the 3 shown electrical machine and the position of the air guide element;
• 5 : a side view of a partial section of the rotor of an electrical machine according to the invention;
• 6 : an enlarged view of in 5 shown detail A and the position of the air guide element;
• 7 : a front view of the 5 shown section BB, which shows the position of the air guide element; and
• 8th : Diagrams of practical tests showing the temperature distribution in the rotor coil head (top of the diagram) and the air velocity distribution in the radial direction at the air inlet of the coil head (bottom of the diagram) with and without an air guide element according to the invention.

Detailed description of the invention

The present invention relates to an air guide element (100) for balancing the air flow that cools a coil head (200) of the poles (300) of the rotor (400) of a rotating electrical machine. The air guide element retains a portion of the air flow in an area with increased air supply (210) and directs it into an area with lower air supply (220).

In the context of the present invention, the term "air flow" refers to any and all air movements, be it axial or radial or mixed, caused by the rotation of the rotor (400) in its protruding elements and/or projections and/or bumps and/or the like, for example, among others, on the ribs of the shaft (410) and/or on the rotor press ring (420) and/or on another element or part of the rotor (400).

In the context of the present invention, the term "region of increased air supply" (210) refers to the part of the coil head (200) that receives a volume of air from the total amount of air that reaches the coil head (200) that is greater than the volume of air that a "region of reduced air supply" (220) receives. These regions (210, 220) have neither a defined nor a clear size, and there is no defined or clear boundary between them. Rather, they should be understood as regions (210, 220) with variable size and boundaries that change according to the conditions and dynamics of the air movement that flows through them.

The region with increased air supply (210) is usually, among others, the one that is axially furthest from the free end of the coil head (200), or the region that is furthest from the turning points or windings of the turns (201), or the region that is adjacent to the axially innermost structure (421) of the rotor press ring (420), while the region with reduced air supply (220) is usually, among others, the one that is axially closest to the free end of the coil head (200), or is closer to or further from the turning points or windings of the turns (201), or the region that is adjacent to the axially outermost structure (422) of the rotor press ring (420). It should be noted that this condition may be reversed or different depending on the rotor structure (400) and the characteristics of the rotating electrical machine, which ultimately requires a different positioning of the air guide element (100).

The term “equilibrium” therefore refers to the equalization or redistribution of air flows with different flow and/or pressure characteristics and/or intensities and/or velocities. The goal is to achieve maximum air delivery in all parts of the coil head (200). This is achieved by partially withholding the flow, thereby reducing the volume of air reaching the area of increased air delivery (210). The excess volume is diverted by the air guide element (100) to increase the volume of air reaching the area of reduced air delivery (220). In this way, balancing of the air delivery in these two areas (210, 220) is promoted.

The air guiding elements (100) are arranged under the coil heads (200) in the radial space between the poles (300) and the rotor (400), in particular in the area with increased air supply (210), in a position close to the axially innermost structure (421) of the rotor press ring (420) which is closest to the rotor package (430) and is arranged substantially centrally with respect to each of the poles (300). Therefore, there must be at least one air guiding element (100) per pole (300).

It should be noted that the term "close" should not be interpreted in a restrictive manner and can include both an inclined position with no play and a close position with slight clearance or minimal play.

Each air guiding element (100) comprises a base body (105) which is substantially polygonal, elongated, thin and curved with a radius which is preferably adapted to the radius of the rotor (400), the air guiding element (100) having substantially two longer edges (110, 120) which preferably run perpendicular to the longitudinal axis of the rotor (400) and two shorter edges (130, 140) which preferably run parallel to the longitudinal axis of the rotor (400). However, the longer (110, 120) and shorter edges (130, 140) may have a geometry deviating from the preferred geometry without losing the technical effect produced, as long as the other geometric relationships of the series of openings (150) are maintained. Thus, the longer edges (110, 120) can enclose an angle other than 90° to the longitudinal axis of the rotor (400), just as the shorter edges (130, 140) can enclose an angle other than 0° to the longitudinal axis of the rotor (400).

Adjacent to the longer inner edge (110) there is an inner flap (111) which runs substantially perpendicular to the surface of the body (105), which extends towards the axis of the rotor (400) and serves to attach the air guide element (100) to the axially innermost structure (421) of the rotor press ring (420).

Adjacent to the longer outer edge (120) there is at least one outer flap (121), preferably perpendicular to the surface of the body (105) and therefore preferably parallel to the inner flap (111), which extends in the direction of the turns (201) of the coil head (200). This can finally adjoin the radial support section (423) of the coil head (200), which in an exemplary embodiment can be understood as the inner surface of the struts (423) of the rotor press ring (420). This structure serves to control the air flow passing through the air guide element (100) and to prevent the passing air from deviating in random directions.

The length or the dimension of the arc (106) of the longer edges (110, 120) covers between 30 and 80%, preferably between 55 and 65% of the length or the dimension of the arc (301) of a pole (300). The width (107) or the dimension of the shorter edges (130, 140) or the dimension between the flaps (111, 121) covers between 30 and 80%, preferably between 40 and 75% of the axial distance of the free/ventilated section (202) of the coil head (200), which is usually the section of the coil head (200) that protrudes beyond the edge of the stack (430) of the rotor (400).

The air guiding element (100) comprises at least one, preferably more than one opening (150) for the passage of air in the form of recesses on the base body (105), wherein these are preferably, but not necessarily, grouped and arranged equidistantly from one another. This forms a row of openings (150) which are preferably arranged asymmetrically with respect to the edges (110, 120, 130, 140) and preferably closer to the longer inner edge (110) than to the longer outer edge (120). In relation to the direction of rotation of the rotor (400), they are preferably closer to the shorter edge (130) upstream than downstream to the shorter edge (140). The distance (152) between the first opening (150) and the longer inner edge (110) is preferably a value of 0.1 to 10%, preferably 0.5 to 8% of the length (107) of the shorter edges (120, 130). The distance (153) between the first opening (150) and the shorter edge (130) upstream is preferably a value of 1 to 40%, preferably 5 to 25% of the length or dimension of the arc (106) of the longer edges (110, 120). In machines with bidirectional rotation, a different positioning of the openings (150) may be required, such as a symmetrical arrangement with respect to the shorter edges (130, 140).

The shape of the openings (150) can be polygonal and symmetrical, polygonal and asymmetrical, circular, oval, elongated or any other suitable shape, with an elongated polygonal shape being preferred.

The sum of the areas of the recesses forming the openings (150) corresponds to a value between 1 and 35%, preferably between 3 and 25%, particularly preferably between 5 and 15% of the total surface of the base body (105).

Therefore, the air flow moving radially from the region of the axis of the rotor (400) towards the coil heads (200) is partially retained when it reaches the air guide element (100). Only the amount of air that flows through the openings (150) for the air passage is allowed to pass, while excess air that is retained in the closed part of the base body (105) is deflected and directed to the edges (120, 130, 140). In this way, the amount of air that reaches the region with increased air supply (210) is reduced in favor of an increase in the volume of air that reaches the region with lower air supply (220). This leads to an even distribution and therefore an equalization or equalization of the volume of air that reaches the coil head (200).

Therefore, the air guide element (100) is arranged under the coil heads (200) in a position closest to the area of increased air supply (210) and substantially central or midway with respect to the poles (300). With the dimensions and areas described, it can equalize the distribution of the air flow generated by the movement of the rotor (400) and redirect it from a more ventilated area to a less ventilated area.

Practical tests and temperature simulations prove the effectiveness of the air guide element (100) according to the invention, the use of which not only leads to a reduction in the temperature at the already existing hot spots of the coil head (200), but also to a significant reduction in the temperature peak values, whereby the temperature difference between the highest and the lowest temperature is reduced by more than 50% compared to a similar machine without air guide element (100), as shown in the diagram in 8th Furthermore, graphical analyses of the air velocity distribution in the radial direction at the air inlet of the coil head (200) demonstrate the almost complete equalization of the air flow distribution.

The air guiding elements (100) can be attached to one or more elements of the rotor structure (400) by any suitable means or fastening element selected from the group consisting of screws, pins, rivets, welds, high-performance adhesives, fittings, clamps and the like, individually or in combination with one another.

The air guiding elements (100) can be made of any material suitable for the application. The material can be selected from the group comprising metals and their alloys, thermoplastic or thermosetting polymers, alone or in combination with one another.

By attaching the air guide element (100) to one or more highly dimensionally stable elements of the rotor structure (400), such as the rotor press ring structure (420), it is also ensured that even at high speeds, significant deformations of the air guide elements during operation are avoided or minimized. This ensures the effectiveness of the air guide elements (100) in almost all areas of application and conditions of the rotating electrical machine.

Finally, a rotating electrical machine according to the invention is a four-pole turbo generator which is constructed with solid poles and is provided with at least one air guide element (100) according to the invention.

Conclusion

It will be readily apparent to those skilled in the art that modifications can be made to the present invention without departing from the spirit and scope of the invention as set forth in the specification. Such modifications are considered to be within the scope of the present invention. Accordingly, the specific embodiments described in detail herein are only illustrative and exemplary and are not limiting of the scope of the present invention, which is to be given the full breadth of the appended claims and all equivalents thereof.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely to provide the reader with better information. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• WO 2020021673 [0009, 0010]

Claims (12)

Air guide element for the coil head of rotors of rotating electrical machines, characterized in that it is arranged under the coil heads (200) in a position which is closest to the area with increased air supply (210) and is substantially central or midway with respect to each of the poles (300). Air guide element according to Claim 1 , characterized in that it comprises a base body (105) which is provided with two longer edges (110, 120) preferably lying perpendicular to the longitudinal axis of the rotor (400) and two shorter edges (130, 140) preferably lying parallel to the longitudinal axis of the rotor (400). Air guide element according to Claim 1 , characterized in that it comprises openings (150) for the passage of air, which are grouped and preferably arranged asymmetrically with respect to the longer edges (110, 120), preferably being arranged closer to the longer inner edge (110). Air guide element according to Claim 3 , characterized in that the distance (152) between the first opening (150) and the longer inner edge (110) is preferably a value of 0.1 to 10%, preferably 0.5 to 8% of the length (107) of the shorter edges (120, 130). Air guide element according to Claim 1 , characterized in that the openings (150) are preferably arranged asymmetrically with respect to the shorter edges (130, 140), wherein they are preferably arranged closer to the shorter edge (130) upstream with respect to the direction of rotation of the rotor (400). Air guide element according to Claim 5 , characterized in that the distance (153) between the first opening (150) and the shorter edge (130) upstream is preferably a value of 1 to 40%, preferably 5 to 25% of the length or dimension of the arc (106) of the longer edges (110, 120). Air guide element according to Claim 1 , characterized in that the sum of the areas of the cutouts forming the openings (150) corresponds to a value between 1 and 35%, preferably between 3 and 25%, particularly preferably between 5 and 15% of the total surface of the base body (105). Air guide element according to Claim 1 , characterized in that the length or the dimension of the arc (106) of the longer edges (110, 120) covers between 30 and 80%, preferably between 55 and 65% of the length or the dimension of the arc (301) of a pole (300). Air guide element according to Claim 1 , characterized in that the width (107) or the dimension of the shorter edges (130, 140) or the dimension between the flaps (111, 121) covers between 30 and 80%, preferably between 40 and 75% of the axial distance of the free/ventilated section (202) of the coil head (200). Air guide element according to Claim 1 , characterized in that it comprises at least one outer flap (121) which is preferably perpendicular to the surface of the body (105) and extends in the direction of the turns (201) of the coil head (200), whereby it can adjoin the surfaces of the radial support portion (423) of the coil head (200). Air guide element according to Claim 1 , characterized in that it is attached to the axially innermost structure (421) of the rotor press ring (420) and/or to one or more elements of the rotor structure (400). Rotating electrical machine, characterized in that it is a turbo generator with four solid poles, which is provided with at least one air guide element (100) according to one of the Claims 1 until 6 is provided.

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