WO2009142566A1

WO2009142566A1 - Device in an electric generator

Info

Publication number: WO2009142566A1
Application number: PCT/SE2009/000213
Authority: WO
Inventors: Leif Jonson
Original assignee: E.On Es Sverige Ab
Priority date: 2008-05-19
Filing date: 2009-04-24
Publication date: 2009-11-26
Also published as: SE0801149L; SE532417C2

Abstract

A support arrangement (1) for a stator device (2) of an electric generator, extending in ring shape around a vertically oriented symmetry axis (A), wherein the support arrangement (1) includes on the one hand a number of vertical support units (3) arranged to be distributed over the circumference of the stator device for transferring the force of gravity of the stator device (2) to a foundation (5), on the other hand a number of horizontal support units (4) for anchoring the stator device (2) in horizontal direction in respect of the foundation (5), wherein each vertical support unit (3) includes one first support element (6) being fastenable against a lower side of the stator device (2) and a second support element (7) being fastenable to the foundation. The vertical support unit (5) includes a flexible element (8) in the form of a layer of flexible material (8) applied between the first (6) and the second (7) support element for allowing a relative movement in a radial direction of the stator device (2) between these support elements. The invention also concerns a vertical support unit (3) and a method for frequency tuning.

Description

DEVICE IN AN ELECTRIC GENERATOR

FIELD OF THE INVENTION

The invention concerns a support arrangement for a stator device of an electric generator according to the preamble of claim 1. The invention also relates to a vertical support unit being included in such a support arrangement as well as a method for frequency tuning.

BACKGROUND OF THE INVENTION

GB 1 403 090 shows an example of a support arrangement for a stator device of a dynamo-electric machine, wherein a stator device rests on support feet for receiving vertical load and further is rotationally stabilized by tangentially aligned anchoring means. The support feet have a lower base portion and an upper stator portion, wherebetween mutual movement in radial direction is possible. The reason for this is to allow the stator device to be able to expand radially without great breaking forces occurring in the foundation in connection with heating of the stator from a cold state during operation. Besides influencing the foundation, there is also a risk that a rigid or erroneous support construction can lead to subjecting plates in the stator core for unwanted buckling tendencies . The slide guides shown in the patent document are problematic, i.a. because of unforeseeable friction between the parts of the support feet and high demand for maintenance, which results in that the entire plant relatively often can be required to be shut off for repair and service. Because of the very high weight of the stator, the support feet are produced from rigid, load supporting plates, between which relative movement is intended. Other examples of the background art are described in JP58015455 and JP58015454, which documents show different embodiments of arrangements with flexible steel strips (different elements) , which are fastened on the one hand in the stator device, in the other hand to the foundation, and which allows radial expansion of the heated stator device through elastic deflection in radial direction. A problem with this solution is that of the necessary increased space requirement for the arrangement, which can result in that such arrangements are not applicable in certain applications.

As background art also US 3 387 152 and US 5 117 140 can be mentioned.

AIM AND MOST IMPORTANT FEATURES OF THE INVENTION It is an aim of the present invention to provide a support arrangement, as stated initially, wherein the drawbacks of the background art are avoided or at least mitigated. It is further an aim with the present invention to provide a support arrangement, which allows use in existing plants as replacements for existing support arrangements, as well as in new plants wherein space-saving support arrangements with long working life is desired.

These aims are obtained in an arrangement as mentioned above through the characterizing features of claim 1. Hereby is achieved that the stator device is allowed to expand without great breaking forces being transferred to the foundation at the same time as movement between contacting surfaces is avoided. It is further achieved that a very compact arrangement is made possible, which can be applied in existing plants where there is a shortage of space as well as in new plants. In particular it is the combination of vertical support units and horizontal support units that altogether according to the invention gives the unexpected and advantageous result.

The function of the vertical support unit is to transfer the force of gravity of the stator to the foundation and allow a radial movement of the stator relative thereto. This movement is a result of the length expansion of the stator because of heating in operation.

The function of the horizontal support unit is to transfer horizontal forces acting on the stator to the foundation. With horizontal forces are intended also force couples being reaction forces against the brake torque which acts between stator and rotor.

The properties and dimensions for the flexible element may be tested of the person skilled in the art for the respective application, wherein can be mentioned that choice of material is determined also in respect of resistance against heating etc.

In a preferred embodiment, the flexible element is a layer of a rubber material or a rubber-like material, which is arranged, fastened against the first as well as the second support element . Hereby it can be mentioned that the height of the flexible element is calculated based on expected expansion such that the shearing strain in the material is within acceptable limits. The dimensional extension of the respective flexible element in the horizontal plane is determined from the prevailing load.

In a variant of the invention the flexible element is a polymeric low friction material, which is fastened to one of the support elements and exerts low friction against the other one of the support elements. A preferred example of such a material is a plate of PTFE (Teflon ^®) .

The flexible element is suitably plate-shaped and oriented with a main plane disposed essentially horizontally, which allows simple construction and installation of the support arrangement .

Each horizontal support unit includes at least one strut capable of receiving tensile or compressive forces, occurring during operation of the generator. This gives a reliable construction which is easy to install. It is particularly preferred that each horizontal support unit is arranged close to a vertical support unit and in particular as an integral unit therewith. It is further suitable that each horizontal support unit on the one hand is fastened to a first support element and on the other hand to a fastener being arranged on the foundation.

The first support element is preferably arranged with such a play in rotational direction to the fastener that the latter serves as a rotational stop at possible occurrence of abnormal rotational forces on the stator device.

The invention also concerns a vertical support unit according to the above wherein advantages corresponding to the ones mentioned above are achieved. The vertical support unit is characterized by applicable corresponding features as the support arrangement itself.

The invention also concerns a method for frequency tuning of a system including a stator of an electric generator and a support arrangement according to the above . According to the invention, horizontal support units being included in the system are adjusted in respect of the foundation as concerns the number and rigidity of the horizontal support units such that the natural frequency of the system for rotational movements around its central axis deviates a predetermined degree from an excitation frequency affecting the system.

In particular the dimensions in length and cross sectional direction of the horizontal support units being included in the system are adjusted. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail by way of the embodiments with reference to the annexed drawings, wherein: Fig. 1 diagrammatically shows a stator device resting on a foundation over an inventive support arrangement,

Fig. 2 diagrammatically shows the support arrangement in Fig. 1 with the stator device removed,

Figs. 3 and 4 in different views showing details of the support arrangement in Figs. 1 and 2 in larger scale,

Fig. 5 shows a unit being included in an alternative support arrangement in a perspective view, and

Fig. 6 shows the unit in Fig. 5 in a plane view.

DESCRIPTION OF EMBODIMENTS

In Fig. 1 is shown a support arrangement 1 for a stator device 2 of a not shown electric generator, the stator device 2 extending around a vertically oriented symmetry axis A. The support arrangement 1 rests on a foundation 5. The stator device 2, the foundation 5 and the not shown electric generator is of a kind that is well known within the field and will therefore not be described further here.

The support arrangement 1 includes a number of vertical support units 3 which are distributed over the circumference of the stator device below a lower limiting surface of the stator device for transferring the force of gravity thereof to the foundation 5.

Further, the support arrangement 1 provides a number of horizontals support units 4 for anchoring of the stator device in a horizontal direction in respect of the foundation 5, such that the stator device is essentially prevented from moving in rotational direction around the axis A. It should, however, be noted that limited movements of the stator in radial direction caused by heating is allowed by the horizontal support units 4. For that reason the horizontal support unit has a flexing capability in a radial direction of the stator device, such that it can expand radially under a certain deflection of the horizontal support units when the stator device is heated in operation of the plant. Besides, they have preferably a certain flexing capability in the vertical direction in order to be capable of functioning at downward yielding of, and certain possible permanent sinkage in the rubber material . By the construction of the horizontal support units with slim crosswise dimensions, they will not present any significant resistant against the radial movement of the stator.

In Fig. 2 the support arrangement 1 is shown with removed stator device, wherein is evident that in this case six vertical support units 3 and six horizontal support units 4 are arranged. The number of these units can be higher or lower depending on the application.

It is further not necessary that the number of horizontal support units 4 is the same as the number of vertical support units 3. Because of space reasons, also the horizontal support units and the vertical support units can be positioned at a distance from each other and be independent of each other. It is, however, suitable to co-ordinate the positioning based on for example cast-in respectively existing steel plates in the foundation.

Referring to Fig. 3, each vertical support unit 3 has a first support element 6 which is fastened to a lower side of the stator device 2 and a second support element 7 which is fastened to the foundation 5. Between the first and the second support element is placed a flexible element 8 of a rubber material or a rubber-like material, which is fastened in a suitable manner such as for example by vulcanizing or gluing against the first as well as the second support element. This arrangement allows a relative movement in radial direction, as seen of the stator device, between these support elements under simultaneous providing a certain stabilizing return force . The horizontal support unit 4 on Fig. 3 includes a stator fastener 9, a foundation fastener 10 and a strut 11. The strut is here in the form of a rounded steel rod, which is rigidly attached to the stator fastener as well as to the foundation fastener, but which because of its length extension tolerates a displacement in radial direction of these fasteners in respect of each other, because of respective heating and cooling of the stator device 2.

The horizontal support unit 4 is positioned such that the forces occurring in operation of the electric generator are received by the strut 11. This can be the form of tractive, compressive as well as bending forces. The positioning is suitably optimized such that the expected greatest occurring forces will be received as tensile forces in the struts, which thus receive these forces by tensile stresses in the material . In some applications it is suitable to arrange struts for similar reception of compressive as well as tensile forces.

In this connection can be mentioned that besides rotational forces, which are reaction forces caused by a braking movement in operation, also translation forces on the stator device occurs in operation, originating from on the one hand that the rotor is not rotating completely concentrically with the stator device, on the other hand because of that the rotor can be somewhat eccentric, i.e. have a magnetically centre deviating from the stator centre. It is thus the task of the arrangement with horizontal support units to receive these forces and transfer them to the foundation. The reaction forces are mainly received by these struts having a direction in the horizontal plane being parallel with the force direction and in reduced degree also by the other struts.

Each strut in form of for example a rod has a direction in the horizontal plane which is parallel to the tangential direction of the stator where the strut is fastened to the stator. The respective strut further is slim such that it will not give any significant resistance (by bending or pulling) against the radial movements of the stator.

The nature of the horizontal support units is to be flexible for radial forces (and also vertical forces) in order to allow the vertical support units to work in a way that is as balanced as possible. An alternative adequate term for "horizontal support unit" is "horizontal force receiver" .

In Fig. 4 the details of the vertical support unit 3 and the horizontal support unit 4 respectively are shown from another angle, whereof is shown on the one hand the construction of the vertical support unit 3 with rectangular shape to the first and second support elements and of the flexible element. The fasteners have a stabilizing U-shape, as seen in vertical views. The fasteners are usually intended and constructed to be welded to the lower plate of the stator device and a foundation plate, respectively.

Figs. 5 and 6 illustrate an alternative embodiment of a unit being included in an inventive support arrangement. Similar to the previously mentioned embodiment, this unit is arranged to be positioned with a number of units distributed over the circumference of the stator device in a manner corresponding to what is shown in Fig. 2. In this case, however, the vertical support unit 3' is integrated with the horizontal support unit in such a way that a first support element 6' on the one hand in the same way as is described for the previous embodiment co-operates with a second support element 7' over a flexible element 8', on the other hand has fastening means 13 which co-operates with struts 11' .

On these figures there are, as an example only, being arranged two struts 11' which also co-operate with a foundation fastener 10' which in turn is fastened to a foundation plate 5', which in turn in a suitable manner is fastened to a foundation through bolting, casting in or in any other way.

The first support element 6' has an upwardly directed recess 12 for a force transferring wedge, which is intended to co-operate with a corresponding groove on a not shown foot of a stator device. The groove 12 is intended to be aligned radially in respect of the stator.

The foundation fastener 10' has besides holes for co- operating with the struts 11', a central portion indicated with 14, with which is arranged a rotational stop for the first support element 6' and thereby for the stator device in operation. The rotational stop is intended to receive and prevent excessive movements of the stator device, which could otherwise occur during unusual operational conditions. The rotational stop is at 14 arranged such that the first support element 6' has an abutment surface 15 being positioned with a chosen play against the corresponding abutment surface on the foundation fastener 10' . The rotational stop also works in the other direction through an adjustable screw arrangement, whereby screws drawn into the first support element 6' and passing not shown holes in the foundation fastener 10' have an abutment surface 16, which is positionable in a chosen distance on a corresponding abutment surface on the foundation fastener 10' for having a corresponding play.

The invention can be modified within the scope of the following claims and in one embodiment the arrangement is provided with a force transferring wedge for positioning in the wedge groove 12, said force transferring wedge also possibly having recesses for surrounding the respective struts 11' for protection against overload and cracking thereof.

The struts can be arranged with another cross sectional form than circular, for example have a rectangular cross section.

The fastening between strut and fastener and support element respectively can be made differently, which will be evident for the person skilled in the art. The horizontal support units and vertical support units can instead of being positioned below the stator device be positioned entirely or partly outside it if desired because of for example space requirement reasons.

In the embodiment where the flexible element is of a low friction material, such as PTFE, it is obtained in respect of the background art unexpected properties, since the levelling character of the flexible material gives relatively low surface pressure and predetermined and very low friction.

A consequence of the invention is that the system stator and horizontal support units (struts) forms an elastic system with a certain natural frequency which can be tuned by varying the rigidity of the struts such that this natural frequency significantly differs from the excitation frequency which occurs during unusual operational cases, such as short transient moment occurring between rotor and stator at short circuit of the stator circuit or in case of incorrect face angle during phase synchronization to the network, which excitation frequently is usually 50 Hz or 60 Hz. The moment amplitude can in these load cases be up to 15 times greater than normal braking moment between rotor and stator.

Through variation or lengths, cross-sectional dimensions and number of horizontal support units, the system can be given a natural frequency which is on a safe distance from said excitation frequency. It is desired to have a natural frequency below 40 Hz of the system and most preferred below 30 Hz (for excitation frequency of 50 Hz) in order to get as small as desired amplification factor. This way is avoided unwanted influence from natural vibrations of the system which would otherwise be amplifying on unwanted forces and moments affecting the stator in operation.

With the construction shown in Figures 1 and 2 of the horizontal support units with screw fastenings of struts vis- a-vis the fasteners it is given an advantageous possibility of adjusting the position of the stator in the horizontal plane by using the screw fasteners for fine adjustment of the horizontal position, wherein the person skilled in the art understands that a suitable screw adjustment of these fastenings provokes movement at desired direction and degree.

Claims

C L A I M S

1. Support arrangement (1) for a stator device (2) of an electric generator, said stator device extending in ring shape around a vertically oriented symmetry axis (A) , wherein the support arrangement (1) includes on the one hand a number of vertical support units (3) arranged to be distributed over the circumference of the stator device for transferring the force of gravity of the stator device (2) to a foundation (5) , on the other hand a number of horizontal support units (4) for anchoring the stator device (2) in horizontal direction in respect of the foundation (5) , wherein each vertical support unit (3) includes one first support element (6) being fastenable against a lower side of the stator device (2) and a second support element (7) being fastenable to the foundation, c h a r a c t e r i z e d in that the vertical support unit (5) includes a flexible element (8) in the form of a layer of flexible material (8) applied between the first (6) and the second (7) support element for allowing a relative movement in a radial direction of the stator device (2) between these support elements.

2. Support arrangement according to claim 1, c h a r a c t e r i z e d in that the flexible material (8) is a rubber material or a rubber-like material which is arranged fastened against the first (6) as well as the second (7) support element.

3. Support arrangement according to claim 1, c h a r a c t e r i z e d in that the flexible material (8) is a polymeric low friction material, which is fastened to one of the first (6) and second (7) support element and exerts low friction against another one of the first (6) and the second

(7) support element.

4. Support arrangement according to any one of the claims 1 - 3, c h a r a c t e r i z e d in that the flexible element

(8) is plate-shaped and oriented with a main plane disposed essentially horizontally.

5. Support arrangement according to any one of the claims 1 - 4, c h a r a c t e r i z e d in that each horizontal support unit (4) includes at least one strut (11) .

6. Support arrangement according to any one of the claims 1 - 5, c h a r a c t e r i z e d in that each horizontal support unit (4) is arranged adjacent to a vertical support unit (3) .

7. Support arrangement according to claim 6, c h a r a c t e r i z e d in that each horizontal support unit (4') is arranged as an integral unit together with a vertical support unit (3') .

8. Support arrangement according to any one of the previous claims, c h a r a c t e r i z e d in that each horizontal support unit (4) on the one hand is fastened to a first support element (6) and on the other hand to a fastener (10) which is arranged on the foundation.

9. Support arrangement according to claim 8, c h a r a c t e r i z e d in that the first support element (6') is arranged with such a play in rotational direction of the fastener (10') that the latter serves as a rotational stop at possible occurrence of abnormal rotational forces on the stator device (2) .

10. Vertical support unit (3) being included in a support arrangement (1) according to any one of the claims 1 - 9, including a first support element (6) being fastenable against a lower side of a stator device (2) and a second support element (7) being fastenable to a foundation, c h a r a c t e r i z e d in that the vertical support unit (5) includes a flexible element (8) in the form of a layer of flexible material (8) applied between the first (6) and the second (7) support element for allowing a relative movement in a radial direction of the stator device (2) between these support elements.

11. Method for frequency tuning of a system including a stator of a electric generator and a support arrangement (1) according to any one of the claims 1 - 9, including adjusting of horizontal support units (4) in the system in respect of the foundation (5) as concerns number and rigidity such that the natural frequency of the system for rotational movements around its central axis deviates by a determined degree from an excitation frequency affecting the system.

12. Method according to claim 11, wherein dimensions in length and cross-sectional direction of horizontal support units (4) being including in the system are adjusted.