Electric connection for a rotor winding of an electrical generator

Field of invention

The present invention relates to an electric generator including a stator and a rotor having a stator winding and a rotor winding, respectively . Particularly, but not exclusively, the present invention may be ef ficiently applied to an electric generator of a wind turbine .

Art Background

An electric generator, such as an electric generator installed in a wind turbine , typically comprises a rotor which rotates relative to a stator . Electric generators are known to have two di f ferent sets of windings : a stator winding and a rotor winding . A so-called Doubly Fed Induction Generator ( DFIG) is for example an electric generator of such type . The rotor and stator windings may be electrically independent from one another and separately connected to the electrical equipment outside the machine , which may be for example used to trans fer electrical power to a utility grid . Such electric generator may further include a slip ring, which is arranged on the rotor shaft and which permits , by means of sliding contacts , to establish an electrical connection between the rotor windings and the external electrical equipment .

It is known to connect the rotor winding to the slip ring through connection wires . The use of a wire connection determines a plurality of drawbacks , for example in terms of time and cost of production . Therefore , the scope of the present invention is to provide an electrical connection between the rotor winding and the slip ring, which may overcome the drawbacks of the prior art .

Summary of the invention

This need may be met by the subj ect matter according to the independent claim . Advantageous embodiments of the present invention are described by the dependent claims .

According to the present invention, it is provided an electrical connector for electrically connecting a rotor of an electric generator to a slip ring . The electrical connector comprises :

- a first support cartridge , the first support cartridge being electrically isolated,

- at least a second support cartridge distanced from the first support cartridge along a longitudinal axis of the electrical connector, the second support cartridge being electrically isolated,

- at least one conductive bar extending along the longitudinal axis , the conductive bar being fixed to the first support cartridge and the second support cartridge ,

- a winding connector for electrically connecting the at least one conductive bar to a rotor winding of the rotor .

An electric generator including the above described electrical connector may be advantageously integrated in a wind turbine . An electric generator including the above described electrical connector may be a Doubly Fed Induction Generator ( DFIG) .

The electrical connector of the present invention provides an electrical connection between the rotor winding and external stationary electrical components without using connection wires . Such solution is characteri zed by modularity and pro- vides time reduction during the manufacturing process and a reduction of costs .

According to embodiments of the invention, the electrical connector comprises a plurality of conductive bars , each conductive bar extending along the longitudinal axis and being fixed to the first support cartridge and the second support cartridge , the plurality of conductive bars being distributed about the longitudinal axis .

According to embodiments of the invention, the electrical connector comprises a hollow housing . The hollow housing provides an external surface of the electrical connector, which may be coupled with an axial cavity provided in the rotor shaft .

According to embodiments of the invention, the electrical connector comprises an insulating filler between the hollow housing and the conductive bars . The insulating filler provides stability to the assembly thus avoiding vibrations and undesired movements .

According to embodiments of the invention, the electrical connector comprises a slip ring connector for providing an electrical connection between the at least one conductive bar and an external surface of the slip ring .

The aspects defined above and further aspects of the present invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment . The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited .

Brief Description of the Drawing Figure 1 shows a scheme section of a wind turbine including an electrical generator according to the present invention, the electric generator being connected to an electric grid .

Figure 2 shows an axonometric view of an electrical connector according to the present invention, to be used in the electrical generator of figure 1 .

Figure 3 shows an axonometric view of a first component of the electrical connector of figure 2 .

Figure 4 shows an axonometric view of a second component of the electrical connector of figure 2 .

Figure 5 shows an axonometric view of a third component of the electrical connector of figure 2 .

Figure 6 shows an axonometric view of a fourth component of the electrical connector of figure 2 .

Figure 7 shows an axonometric view of a fi fth component of the electrical connector of figure 2 .

Detailed Description

The illustrations in the drawings are schematic . It is noted that in di f ferent figures , similar or identical elements are provided with the same reference signs .

Figure 1 shows a simpli fied scheme of an electrical connection between a wind turbine 1 and an electrical grid 2 . The wind turbine 1 a wind rotor 5 having a plurality of wind blades powered from the wind . The wind rotor 5 is rotationally coupled with an electrical generator 10 . The electrical generator 10 converts the mechanical power coming from the wind rotor 5 to an electrical power to be provided to the electrical grid 2 . According to other embodiments of the present invention (not shown) , the electrical generator 10 may be not connected to a wind turbine but to any other source of primary power, di f ferent from the wind . The electrical generator 10 includes a rotor 11 and a stator 12 . The rotor 11 is radially internal to the stator 12 and is rotatable with respect to the stator 12 about a rotational axis . According to other embodiments of the present invention (not shown) , the rotor 11 may be radially external to the stator 12 . The electrical generator 10 is a Doubly Fed Induction Generator ( DFIG) . The rotor 11 and the stator 12 comprises a rotor winding I la and a stator winding 12a, respectively . According to other embodiments of the present invention, the electrical generator 10 may be another type of electrical generator including a rotor winding I la . The rotor winding I la and the stator winding 12a are electrically independent and separately connected to a trans former 30 , for trans forming the electrical power provided by both the rotor winding I la and a stator winding 12a to an electrical voltage compatible with the electrical grid 2 . The rotor winding I la is electrically connected to a frequency converter 25 for trans forming the electrical power provided by the grid to an electrical frequency compatible with the rotor 11 . Between the rotor winding I la and the frequency converter 25 a slip ring 20 is provided, which permits , by means of sliding contacts , for example brushes , to establish an electrical connection between the rotor winding I la and the other stationary electrical components . The frequency converter 25 is connected to the trans former 30 . The stator winding 12a is connected to the trans former 30 via an electrical contactor 31 and a circuit breaker 32 . The output of the trans former 30 is connected to the electrical grid 2 via a switch gear 35 .

Figures 2 to 7 show an electrical connector 100 for electrically connecting the rotor winding I la of the rotor 11 to the slip ring 20 . The electrical connector 100 has an elongated shape and extend along a longitudinal axis Y . The electrical connector 100 may be housed inside a cavity 16 of a rotor shaft 15 of the rotor 11 . The cavity 16 and the longitudinal axis Y may be parallel or coincident with a rotational axis of the rotor shaft 15 . According to the present invention, the electrical connector 100 may be used in a new electrical generator 10 or for refurbishing an existing electrical generator . The electrical connector 100 comprises a first support cartridge 110 and a second support cartridge 120 , distanced from the first support cartridge 110 along the longitudinal axis Y . The first support cartridge 110 and the second support cartridge 120 are electrically isolated . For example , the first support cartridge 110 and the second support cartridge 120 may be made from a molded or machined insulated material . According to other embodiments of the present invention (not shown) , the electrical connector 100 may comprise more than two support cartridges 110 , 120 . The electrical connector 100 further comprises one or more conductive bar 130 ( three conductive bars 130 in the embodiment of the attached figures ) extending along the longitudinal axis Y . As shown in the attached figures , a plurality of conductive bars 130 may be distributed about the longitudinal axis Y . In particular, the plurality of conductive bars 130 may be regularly distributed about the longitudinal axis Y ( as shown in figure 3 , each of the three conductive bar 130 is angularly distanced from the other two conductive bars 130 of an angle of 120 ° , measured about the longitudinal axis Y) . The conductive bar 130 are made of copper . According to other embodiments of the present invention, the conductive bar 130 may be made of another conductive material . The conductive bars 130 are fixed to the first support cartridge 110 and the second support cartridge 110 . In embodiments including more than two support cartridges , the conductive bars 130 may be fixed to two or more support cartridges . Each conductive bar 130 extends from a first longitudinal end 131 to a second opposite longitudinal 132 . The first longitudinal end 131 and the second opposite longitudinal 132 are respectively coupled with the first support cartridge 110 and the second support cartridge 120 . Each conductive bar 130 further comprises an in- termediate bar portion 133 extending between the first support cartridge 110 and the second support cartridge 120 .

The electrical connector 100 comprises a winding connector 140 for electrically connecting the at least one conductive bar 130 to the rotor winding I la . The winding connector 140 may be connected, for example by means or screws or by welding, to the first longitudinal end 131 of at least one conductive bar 130 . A connection plate 145 is used for fixing the winding connector 140 to the conductive bar 130 , in such a way that the conductive bar 130 is interposed between the winding connector 140 and the connection plate 145 . In such embodiment the connection plate 145 act as a counterpart for the connection with the winding connector 140 , i . e . screws or bolts passing through holes provided on the conductive bar 130 may be active between the winding connector 140 and the connection plate 145 . According to other embodiments of the present invention, the connection plate 145 may not be present , i . e . the winding connector 140 may be directly fixed to the at least one conductive bar 130 . The winding connector 140 and the connection plate 145 are electrically conductive . The electrical connector 100 comprises a slip ring connector 170 for electrically connecting at least one conductive bar 130 to the slip ring 20 , in such a way that the electrical power from the rotor winding I la is trans ferred to an external surface 26 of the slip ring 20 , where sliding contacts , for example stationary brushes (not shown in the attached figure ) , are provided . The slip ring connector 170 is electrically conductive . The slip ring connector 170 may be connected, for example by means or screws or by welding, to the second longitudinal end 132 of at least one conductive bar 130 . Another conductive connection plate 145 may be also be used, as described above for the winding connector 140 , for fixing the slip ring connector 170 to the conductive bar 130 , in such a way that the conductive bar 130 is interposed between slip ring connector 170 and the connection plate 145 . The conductive bar ( s ) 130 , the winding connector 140 , the slip ring connector 170 and the connection plate ( s ) 145 are made of materials providing an electrical connection between the rotor winding Ila and the sliding contacts of the slip ring 20. The winding connector 140 and the slip ring connector 170 may be shaped as rigid elements. The winding connector 140 and the slip ring connector 170 may be shaped as plates having an "I" or an "L" or "Z" profile.

The electrical connector 100 further comprises a hollow housing 150. The hollow housing 150 may comprise aluminum or steel, for example stainless steel. The hollow housing 150 may be shaped as a cylindrical hollow wall coaxial with the longitudinal axis Y. The diameter of the hollow housing 150 is dimensioned in order that the electrical connector 100 can be housed in the axial cavity 16 of the rotor shaft 15. The hollow housing 150 may longitudinally extend between the first support cartridge 110 and the second support cartridge 120, about intermediate bar portion 133. In other embodiments of the present invention, the hollow housing 150 may extend also about the first longitudinal end 131 and the second longitudinal end 132. The hollow housing 150 is distanced from the conductive components of the electrical connector 100, in particular from the conductive bar(s) 130, an insulating filler 160 being provided between the hollow housing 150 and the conductive bar(s) 130. The insulating filler 160 may be made of resin. The insulating filler 160 hold the assembly including the conductive bar(s) 130, the first support cartridge 110, the second support cartridge 120, the winding connector 140, the slip ring connector 170 and the connection plate (s) 145, avoiding vibrations and movements.