DE102007000668B4 - Rotor of an electrical machine - Google Patents

Abstract

Rotor (10) of an electrical machine, in particular a hydrogenerator, comprising:
a rotor yoke (12) with axial winding slots (13) distributed around the outer circumference;
Winding bars (14, 15) of a rotor winding which are inserted into the winding slots (13) and whose winding ends (16, 17) emerging axially from the rotor yoke (12) form a winding head (11);
a retaining device (19,...,28) which is designed to retain the winding head (11) against centrifugal forces acting on the winding head (11), wherein the retaining device (19,...,28) comprises a plurality of radial bolts (24), each of which has heads (25) firmly connected to a shaft (31), wherein the retaining device (19,...,28) has a retaining strip (23) which runs in the axial direction on the winding head (11), and the plurality of radial bolts (24) are arranged one behind the other in the axial direction and are designed to press the retaining strip (23) from the outside against the winding head (11);
at least one hammer-shaped recess (19) designed to receive at least one counter-bar (20) provided with threaded holes for screwing in the plurality of radial bolts (24) for fastening the bolts (24) to the outer circumference of an axial extension (21) of the rotor yoke (12) located within the winding head (11), wherein the axial extension (21) is arranged in the winding head (11) and wherein the radial bolts (24) belonging to a respective retaining bar (23) are screwed into a common counter-bar (20); and
Means (28, 32, 33) for securing the plurality of radial bolts (24) against rotation, wherein the radial bolts (24) each have a recess (32) with a rectangular contact surface (33) at the inner end and the radial bolts (24) are secured against rotation by securing strips (28) which are axially inserted into the hammer-shaped recesses (19) and rest against the contact surfaces (33).

Description

TECHNICAL FIELD

The present invention relates to the field of electrical machines. It concerns a rotor of an electrical machine, in particular a hydrogenerator.

STATE OF THE ART

Due to the changing market conditions in the liberalized electricity markets and improved technologies in the field of power electronics, the topic of variable-speed drives for energy production has gained increasing importance. For this purpose, doubly fed asynchronous motors are preferred, especially for power outputs above 60 MVA.

The stator of this machine type is no different from the salient-pole synchronous machines commonly used for this application. Machines of this type are characterized by the fact that they are equipped with a three-phase winding on both the stator and the rotor. The winding heads of the rotor winding are usually arranged on a cylindrical surface (see, for example, the DE 195 13 457 A1 ).

• • Bei kleineren Maschinen wird der gesamte Wickelkopf mit mehreren Lagen aus Stahldraht umwickelt. Dies ist bei grösseren Durchmessern aus herstellungstechnischen Gründen nicht sinnvoll.
• • Bei Maschinen mit Durchmessern grösser als 2 Meter werden die Wickelköpfe entweder durch radiale Bolzen oder Gewindestangen mit einer Halterung auf der axialen Verlängerung des Rotorjochs befestigt, wie dies in der oben genannten Druckschrift beschrieben ist, oder
• • der gesamte Wickelkopf wird von einem aufgeschrumpften Stahlzylinder umgeben, wie dies bei Vollpolsynchronmaschinen bekannt ist.

Due to centrifugal force, the winding bars tend to move radially outward from the center during operation. The difficulty with this winding head design lies in adequately protecting the winding bars against deformation caused by mechanical forces. Three solutions are generally available for this:

• • For smaller machines, the entire winding head is wrapped with several layers of steel wire. This is not practical for larger diameters due to manufacturing reasons.
• • For machines with diameters greater than 2 meters, the winding heads are fixed either by radial bolts or threaded rods with a bracket on the axial extension of the rotor yoke, as described in the above-mentioned publication, or
• • the entire winding head is surrounded by a shrunk-on steel cylinder, as is known from solid-pole synchronous machines.

The DE 195 13 457 A1 focuses primarily on the description of the overall design with the associated winding head support system. The bolts used serve to radially support the rotor winding heads and are anchored in the axially raised rotor yoke (see 4 and 5 The bolts are threaded rods that are screwed into the rotor yoke by screwing them into threaded guides (36) mounted in a support ring arrangement. On the other hand, they absorb the centrifugal forces on the air gap side by means of rectangular individual elements and nuts. The disadvantage of the described system lies in the large number of individual parts and the associated risk of destroying the machine if a bolt or nut is lost.

DE 701 612 A discloses a winding head of a rotor winding of an electrical machine with ring segments fastened to the outside of the winding head against the effect of centrifugal forces, which are fastened to a winding support ring located below the winding head by means of radial screw bolts and nuts.

DE 10 2005 051 349 A1 discloses an anti-twist device for a screw connection with a screw head clamped against a body and with a locking plate positively supported against the body and against a contact surface of the screw head.

GB 1910/14680 A discloses a rotor assembly with windings whose winding ends projecting beyond the pole pieces are secured to an armature shaft by means of a plurality of radial bolts, each having heads rigidly connected to a shaft. In one embodiment, the bolt heads are rounded.

The development described below goes into more detail about the bolts used and in particular their secure fixation.

DESCRIPTION OF THE INVENTION

It is the object of the invention to further develop the rotor mentioned at the outset in such a way that the disadvantages of the known solution are avoided and, in particular, a secure fixation of the radial bolts is achieved.

The problem is solved by the totality of the features of claim 1 and claim 7.

A key feature of the invention is that the radial bolts have heads firmly connected to the shaft. This drastically reduces the number of components used. It also eliminates the risk of external nuts or washers coming loose and damaging or even destroying the machine.

According to one embodiment of the invention, the heads of the radial bolts are integrally connected to the shaft, preferably by forging or welding. This facilitates the use of specially shaped heads.

In order to reduce the air resistance of the rotating rotor, it is advantageous if the heads of the radial bolts have an aerodynamically favorable shape, whereby in particular the heads of the radial bolts are rounded on the upper side and have two straight flanks on opposite sides for tightening the bolts.

According to one aspect of the invention, several radial bolts arranged one behind the other in the axial direction are configured to each press a common, axially extending retaining strip against the winding head from the outside. This achieves a uniform pressure distribution of the tightened bolts on the winding head without having to significantly increase the number of elements used by separate washers. To keep air resistance low in this case as well, the retaining strips have rounded longitudinal edges to improve aerodynamics.

According to a further aspect of the invention, hammer-shaped recesses are provided for fastening the bolts to the outer circumference of an axial extension of the rotor yoke located within the winding head. Counter bars provided with threaded holes for screwing in the radial bolts are inserted into these recesses in the axial direction. In particular, the radial bolts belonging to each retaining bar are screwed into a common counter bar. This not only simplifies assembly but also keeps the number of components small.

Furthermore, means are provided for securing the radial bolts against rotation, wherein in particular the radial bolts each have a recess with a rectangular contact surface at the inner end, and the radial bolts are secured against rotation by securing strips which are axially inserted into the recesses and rest against the contact surfaces.

BRIEF EXPLANATION OF THE FIGURES

• 1 in radialer Richtung von aussen gesehen den Wickelkopf mit einer Rückhaltevorrichtung gemäss einem bevorzugten Ausführungsbeispiel der Erfindung;
• 2 einen vergrösserten Ausschnitt aus 1 mit den aerodynamisch geformten Köpfen der radialen Bolzen;
• 3 eine Draufsicht auf den Wickelkopf aus 1;
• 4 einen vergrösserten Ausschnitt aus 3 mit den Befestigungs- und Sicherungselementen für die radialen Bolzen; und
• 5 in zwei 5(a) und 5(b) zwei unterschiedliche Ansichten eines radialen Bolzens, wie er in der Rückhaltevorrichtung der 1 zum Einsatz kommt.

The invention will be explained in more detail below using exemplary embodiments in conjunction with the drawing.

• 1 in the radial direction from the outside, the winding head with a retaining device according to a preferred embodiment of the invention;
• 2 an enlarged section of 1 with the aerodynamically shaped heads of the radial bolts;
• 3 a top view of the winding head 1 ;
• 4 an enlarged section of 3 with the fastening and locking elements for the radial bolts; and
• 5 in two 5(a) and 5(b) two different views of a radial bolt as used in the retaining device of the 1 is used.

WAYS OF IMPLEMENTING THE INVENTION

The proposed solution is based on the idea of reducing the number of individual parts of the winding head retention device while simultaneously mechanically securing all parts against loosening due to vibration. This significantly increases the safety of the system.

In 1 Viewed radially from the outside, a section of a rotor 10 of a large hydrogenerator/motor with a winding head 11 is shown. The winding head is equipped with a retaining device according to a preferred embodiment of the invention. The basic structure of the rotor 10 can be found in the document cited at the beginning. The rotor 10 has a cylindrical rotor yoke 12 with axial winding slots 13 distributed around the outer circumference. Winding bars 14, 15 of the rotor winding are inserted into the winding slots 13 (each in pairs, one above the other). The winding ends 16, 17 emerging axially from the rotor yoke 12 are bent and electrically connected to one another at the ends by means of round eyelets 18 according to a predetermined winding or phase pattern. The winding ends 16, 17 are part of the winding head 11.

Within the winding head 11, a (cylindrical) axial extension 21 of the rotor yoke 12 extends in the axial direction. The end face of the extension is closed by a press plate 29, on which a plurality of axial clamping bolts 30 are supported, which hold the laminated core of the rotor yoke 12 together in the axial direction. On the outer circumference of the extension 21, several wheel rims 34 are arranged one behind the other in the axial direction, in which hammer-shaped recesses 19 are provided, evenly distributed over the circumference, which serve to secure the retaining device according to the invention for the winding head 11. The retaining The device comprises a plurality of radial bolts 24.

As from 2 and 5 As can be seen, radial bolts 24 are used which have heads 25 firmly connected to the shaft 31. The firm connection of the heads 25 to the bolts 24 is preferably effected by a material bond, for example by forging or welding. Thus, in particular, bolts 24 with forged or permanently welded heads 25 are used. The heads 25 have two opposing straight flanks 26, 27, which serve to tighten the bolts 24 with an open-end wrench or the like. Furthermore, instead of rectangular washers, axially extending retaining strips 23 are used, which distribute the retaining forces of the bolts 24 evenly over the winding or the winding head 11.

The screw heads 25 as well as the retaining strips 23 are further characterized by their aerodynamic shape (round heads 25 and rounded edges of the retaining strips 23), which leads to a reduction of friction losses during operation.

The radial bolts 24 extend radially through the winding head 11 and are received in the hammer-shaped recesses 19 in the axially extended rotor yoke (21). The bolts 24 are held in place by a counter bar 20 with offset threaded holes. Corresponding to the retaining bar 23 on the front, the counter bar 20 extends the length of the rotor yoke extension. Each bolt 24 can thus be individually screwed in and tensioned to the required level. Additional axial spacers 22, through which the bolts 24 extend, are arranged between the winding head 11 and the extension 21 of the rotor yoke 12.

As from 5 As can be seen, the otherwise round bolts 24 have a recess 32 with a rectangular contact surface 33 at the free end. This is due to the following reason: The bolts 24 are tightened to the necessary tension using suitable tools, so that in the final position the straight flanks 26, 27 of the screw heads 25 are transverse to the longitudinal axis of the machine; as shown in 1 and 2 is shown. In this position, the rectangular contact surface 33 of the ends of the bolts 24 runs parallel to the flanks of the hammer-shaped recesses 19. As soon as all bolts 24 of a row (retaining strip 23) are attached, a securing strip 28 ( 4 ) are inserted into the remaining recess. The securing strip 28 is dimensioned such that the bolts 24 can no longer be rotated. This principle allows for a simple way of securing all parts of the restraint device against accidental loosening of the screwed parts. Furthermore, it is also possible to secure the bolts 24 on both sides with an inserted strip in the same way if the ends of the bolts are provided with two parallel contact surfaces. Finally, another securing option would be to provide the bolts 24 with slots at the rear through which a metal wire can be inserted for securing purposes.

LIST OF REFERENCE SYMBOLS

10

rotor

11

winding head

12

Rotor yoke

13

winding groove

14.15

winding rod

16,17

Winding end (cranked)

18

Round eyelet

19

recess

20

Counter bar

21

Extension (rotor yoke)

22

spacer body

23

retaining strip

24

bolt

25

Head (bolt)

26.27

flank

28

fuse strip

29

Press plate

30

clamping bolt

31

shaft

32

recess

33

contact surface

34

rim

Claims (7)

Rotor (10) of an electrical machine, in particular of a hydrogenerator, comprising: a rotor yoke (12) with axial winding slots (13) distributed around the outer circumference; winding bars (14, 15) of a rotor winding, which are inserted into the winding slots (13) and whose winding ends (16, 17) emerging axially from the rotor yoke (12) form a winding head (11); a retaining device (19,...,28) which is designed to retain the winding head (11) against centrifugal forces acting on the winding head (11), wherein the retaining device (19,...,28) comprises a plurality of radial bolts (24), each of which is fixedly connected to heads (25) connected to a shaft (31), wherein the retaining device (19,..,28) has a retaining strip (23) which runs in the axial direction on the winding head (11), and the plurality of radial bolts (24) are arranged one behind the other in the axial direction and are designed to press the retaining strip (23) from the outside against the winding head (11); at least one hammer-shaped recess (19) which is designed to receive at least one counter-bar (20) which is provided with threaded holes for screwing in the plurality of radial bolts (24) for fastening the bolts (24) to the outer circumference of an axial extension (21) of the rotor yoke (12) located within the winding head (11), wherein the axial extension (21) is arranged in the winding head (11) and wherein the radial bolts (24) belonging to a respective holding bar (23) are screwed into a common counter-bar (20); and means (28, 32, 33) for securing the plurality of radial bolts (24) against rotation, wherein the radial bolts (24) each have a recess (32) with a rectangular contact surface (33) at the inner end and the radial bolts (24) are secured against rotation by securing strips (28) which are axially inserted into the hammer-shaped recesses (19) and rest against the contact surfaces (33). Rotor after Claim 1 , characterized in that the heads (25) of the radial bolts (24) are integrally connected to the shaft (31). Rotor after Claim 2 , characterized in that the heads (25) of the radial bolts (24) are welded to the shaft (31). Rotor after Claim 1 or 2 or 3 , characterized in that the heads (25) of the radial bolts (24) have an aerodynamically favorable shape. Rotor after Claim 4 , characterized in that the heads (25) of the radial bolts (24) are rounded on the upper side and have two straight flanks (26, 27) on opposite sides for tightening the bolts (24). Rotor after Claim 1 , characterized in that the retaining strips (23) have rounded longitudinal edges to improve aerodynamics. A rotor (10) of an electrical machine, in particular a hydrogenerator, comprising: a rotor yoke (12) with axial winding slots (13) distributed around the outer circumference; winding bars (14, 15) of a rotor winding, which are inserted into the winding slots (13) and whose winding ends (16, 17) project axially from the rotor yoke (12) form a winding head (11); a retaining device (19,...,28) which is designed to retain the winding head (11) against centrifugal forces acting on the winding head (11), wherein the retaining device (19,...,28) comprises a plurality of radial bolts (24), each of which has heads (25) firmly connected to a shaft (31), wherein the retaining device (19,...,28) has a securing strip (28) which is designed to secure the plurality of bolts (24) against rotation, wherein the radial bolts (24) each have a recess (32) with a rectangular contact surface (33) at the inner end, wherein the securing strip (28) is axially inserted into a hammer-shaped recess (19) formed on the outer circumference of the rotor yoke (12) and is arranged in contact with the rectangular contact surfaces (33).

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