A device for effectively suppressing the corrosion of bearings by the shaft voltage of a doubly-fed generator

Abstract

A device for effectively suppressing the corrosion of the bearing by the shaft voltage of a doubly-fed generator belongs to the technical field of motors, and includes an inverter, a rotating shaft, a rotor core and a stator core. The rotor core is sleeved on the rotating shaft. Both ends of the stator core are respectively installed on the rotating shaft through bearings, and the stator core corresponds to the rotor core. Opposite coils are provided on both the rotor core and the stator core. The coil on the rotor core is electrically connected to the inverter. A grounding device for releasing the shaft voltage is provided on the rotating shaft between the two bearings, and the grounding device does not make frictional contact with the bearings. The inverter provides a high-frequency voltage to the coil of the rotor core. Under the interaction of the coils of the rotor core and the stator core, the rotating shaft and the rotor core rotate together. At the same time, with the cooperation of the grounding device arranged between the two bearings, it is possible to prevent the common-mode voltage formed inside from passing through the bearings, thereby protecting the bearings.

Description

Technical Field

[0001] The present invention belongs to the technical field of motors, and particularly relates to a device for effectively suppressing the corrosion of the bearing by the shaft voltage of a doubly-fed generator. Background Art

[0002] A wind turbine is a power device that converts wind energy into mechanical energy, the mechanical energy drives the rotor to rotate, and finally outputs alternating current. A doubly-fed generator is the most widely used generator in wind turbines. A doubly-fed generator consists of a generator stator, a rotor, a drive-end bearing, a non-drive-end bearing, etc. At present, the failure of the bearing caused by shaft voltage corrosion is the most frequent reason for the removal of the doubly-fed generator from the shelf. Therefore, solving the problem of shaft voltage corrosion of the bearing has become an urgent problem to be solved for the doubly-fed generator. Currently, the method for preventing shaft voltage corrosion of the bearing in a doubly-fed generator is usually to arrange a set of grounding brushes on the outer side of each of the two bearings at both ends of the generator, or only arrange grounding brushes at one end, and the bearing is protected by grounding through the grounding brushes.

[0003] There are currently two technical defects in the existing technology:

[0004] 1. For the grounding brushes of the generator, whether it is two sets of grounding brushes or one set of grounding brushes, the grounding brushes are located outside the generator, while the common-mode voltage is generated inside the generator. The common-mode voltage needs to pass through the bearing first before reaching the grounding brush, resulting in a decrease in the protection effect;

[0005] 2. Whether it is the common-mode voltage or the voltage generated by the end leakage magnetic field, the high-frequency content is high, and the high-frequency voltage cannot be effectively grounded through the grounding brush. Summary of the Invention

[0006] To solve the problems in the existing technology that the common-mode voltage needs to pass through the bearing to complete the release, resulting in the shaft voltage having an impact on the bearing during the release process, and the high-frequency voltage cannot be effectively released, the present invention provides a device for effectively suppressing the corrosion of the bearing by the shaft voltage of a doubly-fed generator.

[0007] The present invention is realized by the following technical solutions:

[0008] A device for effectively suppressing the corrosion of the bearing by the shaft voltage of a doubly-fed generator includes a converter, a rotating shaft, a rotor core, and a stator core. The rotor core is sleeved on the rotating shaft. Both ends of the stator core are installed on the rotating shaft through bearings respectively, and the stator core corresponds to the rotor core. Opposite coils are provided on both the rotor core and the stator core. The coil on the rotor core is electrically connected to the converter. A grounding device for releasing the shaft voltage is provided on the rotating shaft between the two bearings, and the grounding device does not come into frictional contact with the bearing.

[0009] The converter supplies the coil of the rotor core with a high-frequency voltage. Under the interaction of the coils of the rotor core and the stator core, the rotating shaft and the rotor core rotate together. At the same time, in cooperation with the grounding device arranged between the two bearings, it can prevent the common-mode voltage formed inside from passing through the bearings, causing the breakdown of the oil film of the bearings and resulting in the failure of the bearings, thus forming a protection for the bearings.

[0010] A further improvement of the present invention is that the above-mentioned grounding device includes a hard copper long conductor, a conductive short rod and a voltage reduction circuit; the hard copper long conductor is arranged coaxially in the rotating shaft; there are three conductive short rods, namely two inner short rods and one outer short rod, and both the inner short rods and the outer short rod penetrate through the rotating shaft and the hard copper long conductor. The two inner short rods are respectively arranged on the inner sides close to the two bearings opposite to each other, and the outer short rod is arranged on the outer side of the bearing close to the converter; the outer short rod is grounded through the voltage reduction circuit. The inner short rod is close to the inner side of the bearing and close to the bearing, which can effectively prevent the common-mode voltage from entering the inside of the bearing; the inner short rod transfers the common-mode voltage to the outer short rod through the hard copper long conductor, and finally releases it to the ground through the voltage reduction circuit.

[0011] A further improvement of the present invention is that the middle section of the above-mentioned conductive short rod is provided with a first threaded section; a threaded hole matching the first threaded section is opened on the hard copper long conductor. The conductive short rod is fixed by screwing the first threaded section onto the hard copper long conductor.

[0012] A further improvement of the present invention is that the two ends of the above-mentioned conductive short rod are respectively provided with a second threaded section; threaded holes matching the second threaded section are opened on the rotating shaft. By screwing the second threaded section onto the rotating shaft, the firmness of the conductive short rod during rotation can be increased.

[0013] A further improvement of the present invention is that the above-mentioned rotating shaft is provided with tin-plated annular bands corresponding to the conductive short rods respectively. The tin-plated annular bands can improve the introduction of the common-mode voltage.

[0014] A further improvement of the present invention is that the above-mentioned voltage reduction circuit includes a capacitor and a resistor connected in parallel. The capacitor can export the high-frequency voltage, and the resistor can export the DC voltage.

[0015] A further improvement of the present invention is that the above-mentioned grounding device further includes grounding brushes, and the grounding brushes are respectively arranged on the sides of the two bearings facing away from each other. The voltage formed outside the bearings can be released through the grounding brushes.

[0016] A further improvement of the present invention is that a slip ring body and a slip ring brush are arranged between the above-mentioned rotating shaft and the converter; the slip ring body is sleeved on the rotating shaft, and the slip ring brush corresponds to the slip ring body and is electrically connected to the converter. The converter outputs the high-frequency voltage through the cooperation of the slip ring body and the slip ring brush.

[0017] As can be seen from the above technical solutions, the beneficial effects of the present invention are as follows: The converter provides a coil of the rotor core with a high-frequency voltage. Under the interaction of the coils of the rotor core and the stator core, the rotating shaft and the rotor core rotate together. At the same time, with the grounding device arranged between the two bearings, it is possible to avoid the common-mode voltage formed inside passing through the bearings, causing the oil film of the bearings to break down and leading to bearing failure, thereby protecting the bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a schematic structural diagram of a specific embodiment of the present invention.

[0020] In the drawings: 1, converter; 2, slip ring brush; 3, slip ring body; 4, rotor core; 5, stator core; 6, rotating shaft; 7, motor housing; 8, drive-end bearing; 9, non-drive-end bearing; 10, bearing insulation; 11, bearing clearance; 12, hard copper long conductor; 13, inner short rod; 14, outer short rod; 15, fastening nut; 16, tinned ring band; 17, drive-end grounding brush; 18, non-drive-end grounding brush; 19, resistor; 20, capacitor; 21, rolling element. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] In order to make the objectives, features, and advantages of the present invention more obvious and understandable, the technical solutions in the present invention will be clearly and completely described below with reference to the drawings in the specific embodiments of the present invention. Obviously, the embodiments described below are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments in this patent, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this patent.

[0022] As shown in the atta Figure 1As shown in the figure, a device for effectively suppressing the corrosion of the bearing by the shaft voltage of a doubly-fed generator includes an inverter 1, a rotating shaft 6, a rotor core 4, and a stator core 5. The rotor core 4 is sleeved on the rotating shaft 6. Both ends of the stator core 5 are respectively mounted on the rotating shaft 6 through bearings, and the stator core 5 corresponds to the rotor core 4. A motor housing 7 connected to the two bearings is sleeved outside the stator core 5. The bearing includes an inner ring, an outer ring, and rolling elements 21. The inner ring is sleeved on the rotating shaft 6, the outer ring is connected to the stator core 5, and the rolling elements 21 are all between the inner ring and the outer ring to achieve coaxial rotation of the inner ring and the outer ring. An insulating layer 10 is provided on the side wall of the outer ring close to the rolling elements 21. There is a bearing clearance 11 between the rolling elements 21 and the inner ring to fill lubricating grease to form an oil film. The insulating layer 10 of the bearing can isolate part of the conduction of the common-mode voltage and form a protection for the bearing oil film.

[0023] One end of the rotating shaft 6 is the driving end, and the other end is the non-driving end. Therefore, the bearing close to the driving end is the driving-end bearing 8, and the other bearing is the non-driving-end bearing 9.

[0024] Opposite coils are provided on both the rotor core 4 and the stator core 5. The coil on the rotor core 4 is electrically connected to the inverter 1, and the inverter 1 is arranged outside the non-driving-end bearing 9. A slip-ring body 3 and slip-ring brushes 2 are provided between the rotating shaft 6 and the inverter 1. The slip-ring body 3 is sleeved on the rotating shaft 6, and the slip-ring brushes 2 correspond to the slip-ring body 3 and are electrically connected to the inverter 1. The slip-ring body 3 is connected to the coil of the rotor core 4. Therefore, the inverter 1 can output a high-frequency voltage to the coil of the rotor core 4 through the cooperation of the slip-ring body 3 and the slip-ring brushes 2.

[0025] A grounding device for releasing the shaft voltage is provided on the rotating shaft 6 between the driving-end bearing 8 and the non-driving-end bearing 9, and the grounding device does not make frictional contact with the bearing. The inverter 1 provides a high-frequency voltage to the coil of the rotor core 4. Under the interaction of the coils of the rotor core 4 and the stator core 5, the rotating shaft 6 and the rotor core 4 rotate together. At the same time, with the cooperation of the grounding device arranged between the driving-end bearing 8 and the non-driving-end bearing 9, it is possible to avoid the common-mode voltage formed inside passing through the bearing, causing the breakdown of the bearing oil film and resulting in bearing failure, thereby forming a protection for the bearing.

[0026] The grounding device includes grounding brushes. The grounding brushes are respectively provided on the sides of the driving-end bearing 8 and the non-driving-end bearing 9 facing away from each other. The grounding brush close to the driving-end bearing 8 is the driving-end grounding brush 17, and the grounding brush close to the non-driving-end bearing 9 is the non-driving-end grounding brush 18. The voltage formed outside the bearing can be released through the grounding brushes.

[0027] The grounding device further includes a long hard copper conductor 12, a conductive short rod, and a voltage reduction circuit; the long hard copper conductor 12 is coaxially arranged inside the rotating shaft 6. Specifically, a hollow through hole allowing the long hard copper conductor 12 to pass through is provided on the axis of the rotating shaft 6, so as to facilitate the assembly of the long hard copper conductor 12 inside the rotating shaft 6; there are three conductive short rods, namely two inner short rods 13 and one outer short rod 14, and both the inner short rods 13 and the outer short rod 14 penetrate through the rotating shaft 6 and the long hard copper conductor 12. The two inner short rods 13 are respectively arranged on the opposite inner sides close to the driving end bearing 8 and the non-driving end bearing 9, and the outer short rod 14 is arranged on the outer side of the bearing surface close to the converter 1, that is, on the outer side of the non-driving end bearing 9; the outer short rod 14 is grounded through the voltage reduction circuit. The inner short rod 13 is close to the inner side of the bearing and close to the bearing, which can effectively prevent the common mode voltage from entering the inside of the bearing; the inner short rod 13 transfers the common mode voltage to the outer short rod 14 through the long hard copper conductor 12, and finally releases it to the ground through the voltage reduction circuit.

[0028] A first threaded section is provided in the middle section of the conductive short rod; a threaded hole matching the first threaded section is opened on the long hard copper conductor 12. The conductive short rod is fixed by screwing the first threaded section with the long hard copper conductor 12.

[0029] Second threaded sections are respectively provided at both ends of the conductive short rod; threaded holes matching the second threaded sections are opened on the rotating shaft 6. Specifically, grooves corresponding to the conductive short rods are opened on the rotating shaft 6, and fastening nuts 15 matching the second threaded sections are provided in the grooves. The conductive short rod is locked on the rotating shaft 6 by the cooperation connection of the second threaded section and the fastening nut 15, which can increase the firmness of the conductive short rod during rotation.

[0030] Tinned ring belts 16 corresponding to the conductive short rods are provided on the rotating shaft 6. The introduction of the common mode voltage can be improved through the tinned ring belts 16.

[0031] The voltage reduction circuit includes a capacitor 20 and a resistor 19 connected in parallel. The capacitor 20 can export high-frequency voltage, and the resistor 19 can export DC voltage.

[0032] In summary, the operating principle of this device is as follows: The high-frequency components containing common-mode voltage output by the converter 1 will generate common-mode voltage in the motor housing 7, stator core 5, and rotor core 4. The coil leakage magnetic flux at the ends of the stator core 5 and rotor core 4 will also induce stray voltage on the motor housing 7 and the rotating shaft 6. Both of these voltages will generate oil film voltage on the oil film of the bearing, break down the oil film, cause damage to the bearing and deterioration of the grease, resulting in bearing damage. This device forms the function of a damping ring through the tin-plated ring belt 16. The tin-plated ring belt 16 forms a "moat" and bypasses the non-drive-end bearing 9 with the common-mode voltage through the hard copper long conductor 12, conducting the common-mode voltage to the non-drive-end grounding brush 18 side. The common-mode voltage releases the high-frequency voltage component and DC voltage component respectively through the parallel circuit of the capacitor 20 and the resistor 19, finally releases the stray voltage and the common-mode voltage, and ultimately forms good protection for the bearing.

[0033] The converter 1 supplies a voltage containing high-frequency components to the rotor coil through the slip ring brush 2 and the slip ring body 3. This high-frequency voltage will generate high-frequency voltage at various positions due to the mutual parasitic capacitance 20 between the coils of the stator core 5, the coils of the rotor core 4, the rotor core 4, and the motor housing 7. The high-frequency voltage generated by the coils of the stator core 5 and the motor housing 7 can release the voltage through the good grounding of the motor housing 7. The high-frequency voltage generated by the coils of the rotor core 4, the rotor core 4, and the rotating shaft 6 can only pass through the rotating shaft 6, through the drive-end bearing 8, the non-drive-end bearing 9, the drive-end grounding brush 17, and the non-drive-end brush grounding. When flowing through the drive-end grounding brush 17 or the non-drive-end grounding brush 18 from the rotating shaft 6, due to the strength problem of the bearing insulation 10, part of the shaft voltage may exceed the oil film breakdown voltage of the bearing clearance 11, causing the oil film to break down, and then grounding through the drive-end bearing 8 and the non-drive-end bearing 9 and then through the motor housing 7. Similarly, the end leakage magnetic flux of the coils of the rotor core 4 and the stator core 5 will also induce stray voltage between the rotor core 4 and the rotating shaft 6. Like the induced voltage of the common-mode voltage, it may break down the oil film of the bearing clearance 11 and ground through the motor housing 7, causing corrosion of the bearing.

[0034] A tin strip 19 and a conductive bolt 14 are arranged in the inner direction of the drive-end bearing 8, and a tinned ring strip 16 and a conductive inner short rod 13 are arranged in the inner direction of the generator of the non-drive-end bearing 910. The shaft voltage of the rotor core 4 and the shaft 6 can bypass the drive-end bearing 8 and the non-drive-end bearing 9 and be connected to the outside of the grounding brush through a hard copper long conductor 12, so that the shaft voltage jumps over the drive-end bearing 8 and the non-drive-end bearing 9 and directly reaches the position of the conductive outer short rod 14. A tinned ring strip 16 is arranged at the position of the outer short rod 14, and there is a non-drive-end grounding brush 18 nearby. The non-drive-end grounding brush 18 is connected to a parallel circuit of a resistor 19 and a capacitor 20. The resistor 19 can ground the DC component of the voltage, and the capacitor 20 can ground the high-frequency voltage component, which can effectively inhibit the corrosion of the bearing by the shaft voltage.

[0035] For a device for effectively suppressing the corrosion of the bearing by the shaft voltage of a doubly-fed generator according to the present invention, the converter provides a coil of the rotor core with a high-frequency voltage. Under the interaction of the coils of the rotor core and the stator core, the shaft rotates together with the rotor core. At the same time, a grounding device arranged between the two bearings can prevent the common-mode voltage formed inside from passing through the bearing, causing the breakdown of the oil film of the bearing and resulting in the failure of the bearing, thereby protecting the bearing.

[0036] In front of the bearing of the present invention, a conductive tinned ring strip is arranged at the neck position of the shaft voltage, and a hard copper long conductor is arranged for drainage, bypassing the bearing to reduce the voltage at the bearing position.

[0037] In the present invention, the conductive tinned ring strip is made of tinned material with good conductivity, which does not increase the weight of the rotor and does not increase the size, and plays a good role in conducting electricity, blocking the shaft voltage, and forcing grounding;

[0038] In the present invention, the conductive band connection adopts 50Mn18Cr4 non-magnetic steel and a hard copper long conductor with excellent conductivity, which plays a good conduction role;

[0039] In the non-drive-end grounding brush of the present invention, it is grounded through a resistor and capacitor circuit. The DC voltage part can be grounded through the resistor, and the high-frequency part can be grounded through the capacitor, which plays a good role in conducting stray voltage and common-mode voltage.

[0040] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same and similar parts between the embodiments, reference can be made to each other.

[0041] The terms "upper", "lower", "outer side", "inner side", etc. in the description and claims of the present invention and the above-mentioned drawings, if any, are used to distinguish the relative relationships in position and do not have to be given a qualitative definition. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion.

[0042] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus for effectively suppressing the corrosion of the bearing by the shaft voltage of a doubly-fed generator, comprising a converter (1), a rotating shaft (6), a rotor core (4) and a stator core (5), wherein the rotor core (4) is sleeved on the rotating shaft (6), both ends of the stator core (5) are respectively mounted on the rotating shaft (6) through bearings, and the stator core (5) corresponds to the rotor core (4). Opposite coils are provided on both the rotor core (4) and the stator core (5). The coil on the rotor core (4) is electrically connected to the converter (1), and it is characterized in that, A grounding device for releasing shaft voltage is provided on the rotating shaft (6) between two bearings, and the grounding device does not make frictional contact with the bearings; the grounding device includes a hard copper long conductor (12), a conductive short rod, and a voltage-reducing circuit; the hard copper long conductor (12) is coaxially arranged inside the rotating shaft (6); there are three conductive short rods, namely two inner short rods (13) and one outer short rod (14), and both the inner short rods (13) and the outer short rod (14) penetrate through the rotating shaft (6) and the hard copper long conductor (12), the two inner short rods (13) are respectively arranged on the inner sides close to the two bearings opposite to each other, and the outer short rod (14) is arranged on the outer side surface of the bearing close to the converter (1); the outer short rod (14) is grounded through the voltage-reducing circuit.

2. The device for effectively suppressing the corrosion of the bearing by the shaft voltage of the doubly-fed generator according to claim 1, wherein A first threaded section is provided in the middle section of the conductive short rod; a threaded hole matching the first threaded section is provided on the hard copper long conductor (12).

3. An apparatus for effectively suppressing the corrosion of bearings by the shaft voltage of a doubly-fed generator according to claim 2, characterized in that, Second threaded sections are respectively provided at both ends of the conductive short rod; threaded holes matching the second threaded sections are provided on the rotating shaft (6).

4. A device for effectively suppressing the corrosion of the bearing by the shaft voltage of a doubly-fed generator according to claim 1, characterized in that, Tinned ring bands (16) corresponding to the conductive short rods are provided on the rotating shaft (6).

5. An apparatus for effectively suppressing the corrosion of bearings by the shaft voltage of a doubly-fed generator according to claim 1, characterized in that, The voltage-reducing circuit includes a capacitor (20) and a resistor (19) connected in parallel.

6. An apparatus for effectively suppressing the corrosion of bearings by the shaft voltage of a doubly-fed generator according to claim 1, characterized in that, The grounding device further includes grounding brushes, and the grounding brushes are respectively provided on one side of the two bearings facing away from each other.

7. A device for effectively suppressing the corrosion of the bearing by the shaft voltage of a doubly-fed generator according to claim 1, characterized in that, A slip ring body (3) and a slip ring brush (2) are provided between the rotating shaft (6) and the converter (1); the slip ring body (3) is sleeved on the rotating shaft (6), and the slip ring brush (2) corresponds to the slip ring body (3) and is electrically connected to the converter (1).

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