ELECTROMECHANICAL SYSTEM AS WELL AS SUPERIMPOSED GEARING FOR TRANSFERRING ROTATIONAL ENERGY

Abstract

An electromechanical system transfers rotational energy, torque and power in a powertrain coupled with a first, a second and a third machine for energy conversion (2, 3, 4). A superimposed gearing (1) includes a planetary gearbox (7) with a sun gear (8), coupled by a first shaft (5) transferring a torque to the first machine (2), and a planetary gear (9) coupled by a second shaft (6) transferring a torque to the second machine (3). The third machine (4) is configured as a three-phase synchronous machine. An internal gear (10) of the planetary gearbox (7) forms a rotor of the three-phase synchronous machine (4). The internal gear (10) is connected to a housing (15) of the planetary gearbox (7), and permanent magnets (11), exciting the three-phase synchronous machine, are arranged on the internal gear (10) and/or on the housing (15) of the planetary gearbox (7).

Claims

1. An electromechanical system for transferring rotational energy, torque and power in a powertrain, the system comprising: a first, a second and a third machine for energy conversion coupled to the powertrain, wherein the third machine is configured as a three-phase synchronous machine; a superimposed gearing comprising a planetary gearbox comprising: a planetary gearbox housing; a sun gear coupled to the first machine via a first shaft for transferring a torque to the first machine; at least one planetary gear coupled to the second machine via a second shaft for transferring a torque to the second machine; and an internal gear that forms a rotor of the three-phase synchronous machine, wherein the internal gear is connected to the planetary gearbox housing; and permanent magnets arranged at the internal gear and or at the planetary gearbox housing for exciting the three-phase synchronous machine.

2. An electromechanical system in accordance with claim 1, wherein the three-phase synchronous machine is configured as a permanent magnet-excited three-phase synchronous machine and the internal gear of the planetary gearbox is in functional connection with the permanent magnets for exciting the three-phase synchronous machine.

3. An electromechanical system in accordance with claim 1, further comprising a drive electronic system, wherein the three-phase synchronous machine is coupled to the drive electronic system for controlling the energy conversion, and the drive electronic system is configured such that the energy conversion takes place in the three-phase synchronous machine as a function of the energy converted by the first and or second machines.

4. An electromechanical system in accordance with claim 3, wherein the drive electronic system is configured such that the three-phase synchronous machine is operated at least at times in a four-quadrant operation.

5. An electromechanical system in accordance with claim 3, wherein the drive electronic system is configured such that an air gap torque of the three-phase synchronous machine is changed at least at times as a function of the energy converted by the first aid or second machines.

6. An electromechanical system in accordance with claim 1, further comprising at least one additional gearing is arranged between the planetary gearbox and the first and/or the second machine.

7. An electromechanical system in accordance with claim 6, wherein the planetary gearbox is arranged in a common oil chamber with the at least one additional gearing.

8. An electromechanical system in accordance with claim 1, wherein the first or the second machine is configured as a three-phase asynchronous machine connected to a power supply.

9. An electromechanical system in accordance with claim 1, wherein the first or the second machine is configured as an internal combustion engine, a turbo-engine, a wind rotor or a wind turbine.

10. A superimposed gearing comprising: a planetary gearbox comprising: a planetary gearbox housing; a centrally arranged sun gear; at least one planetary gear meshing with the sun gear; a first shaft connected to the sun gear for transferring a torque; a second shaft; at least one planetary gear connected to the second shaft for transferring a torque; and an internal gear of the planetary gearbox is mounted rotatably; and devices for dividing, in a specific manner, torque introduced into the planetary gearbox as a function of a control signal, which is generated on the basis of a current operating situation by a drive electronic system, introduce a braking or acceleration torque into the internal gear, wherein the devices for dividing in a specific manner a torque introduced into the planetary gearbox comprises a three-phase synchronous machine wherein a rotor of the three-phase synchronous machine is formed by the internal gear or by a component connected to the internal gear, wherein the internal gear is connected to the planetary gearbox housing, at which permanent magnets are arranged.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In the drawings:

[0028] FIG. 1 is a schematic view of a powertrain of a wind energy plant; and

[0029] FIG. 2 is schematic view of a powertrain of a processing machine.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] Referring to the drawings, FIG. 1 shows an electromechanical system configured according to the present invention for transferring rotational energy, torque and power, which is used as a powertrain of a wind energy plant. The system is configured, in particular, for the variable-speed transfer of rotational energy, torque and power. The first and second machines for energy conversion 2, 3, are an asynchronous generator 2 as well as a wind rotor 3 in this case, both of which are connected to one another via the main powertrain. The wind rotor 3 of the wind power plant is connected to the asynchronous generator 2 via a rotor power take-off shaft 14, a main gearing 12 and a superimposed gearing 1, which is connected in series therewith and is configured as a planetary gearbox 7. The asynchronous generator 2 is connected to the power grid and converts the power introduced by the wind rotor 3 into the powertrain into electrical energy. It is essential here that the wind rotor 3 and hence the rotor power take-off shaft 14 rotate at variable speed, while the speed of the generator shaft is at least nearly constant.

[0031] A synchronous generator may also be used instead of the asynchronous generator 2. The generator shaft must be synchronous in this case with the grid frequency based on the number of pole pairs.

[0032] The sun gear 8 of the planetary gearbox 7 is connected to the drive shaft 5 of the asynchronous generator 2. In addition, the planetary gears 9 circulating around the sun gear 8 are connected at least indirectly to the rotor power take-off shaft 14 and to the rotor 3 of the wind power plant via the carrier, the planet carrier 6 connected thereto and via the main gearings 12. The planetary gears 9 move, furthermore, the internal gear 10 of the planetary gearbox 7 or are driven by the internal gear 10. The internal gear 10 is connected, in turn, to the housing 15 of the planetary gearbox 7, and the internal gear 10 and the housing 15 are mounted rotatably.

[0033] Permanent magnets are fastened to the housing 15 of the planetary gearbox 7 as well as to the outer wall of the internal gear 10 such that the internal gear 10 with the housing 15 forms the rotor of a higher-poled, permanently excited synchronous machine, which is a third machine for energy conversion 4, and which machine 4 is coupled to the powertrain. The synchronous machine 4 is controlled by a drive electronic system 13 with a frequency converter 16 and is operated as a function of the operating situation such that power is transferred from the synchronous machine 4 to the internal gear 10 or is taken up from the internal gear 10 as needed. It is possible in this manner to introduce a braking torque or an acceleration torque into the internal gear 10 and hence into the powertrain connected to the planetary gearbox 7 as needed.

[0034] The asynchronous generator 2 is blocked at low wind speeds and hence low powers. The power generated by the wind rotor is introduced in this case into the synchronous machine 4 via the rotor power take-off shaft 14, the main gearing 12, the planet carrier 5, the planetary gears 9 and the internal gear 10, so that the synchronous machine is operated as a generator and the electrical energy generated is fed directly into the connected power grid via the drive electronic system 13. As soon as the speed of the wind rotor 3 has approximately reached the nominal speed of the generator shaft of the asynchronous generator 2, the brake of this generator is released and an additional rotation is generated at the generator shaft by the permanently excited synchronous machine 4 until the phase angle and the rotary frequency correspond to the values that are present in the connected grid and the generator 2 can be connected directly to the grid.

[0035] As soon as the asynchronous generator 2 was connected to the power grid, the permanently excited synchronous machine 4 is operated such that it holds only the housing 15 and the internal gear 10 of the planetary gearbox 7, which said internal gear 10 is connected thereto. The permanently excited synchronous machine 4 does not release power into the connected power grid in this operating state, nor does it take up power to a noteworthy extent from the power grid. The result of this is that the power of the powertrain can be fed over a broad range into the connected power grid by means of the asynchronous generator 2 operating at constant speed with a simultaneously sinusoidal voltage and current curve. It is, however, also possible to stop the permanently excited synchronous machine completely in this speed range of the plant when the internal gear 10 is stopped via a suitable braking device.

[0036] As the speed of rotation and hence the speed of the wind rotor 3 increase further, for example, because of wind gusts, the power provided hereby additionally in the powertrain is converted into electrical energy by the rotation of the internal gear 10 configured as the rotor of the synchronous machine 4, and this electrical energy is fed via the drive electronic system 13 into the connected grid. Furthermore, stronger wind gusts can be additionally compensated by adjusting the air gap torque of the permanently excited synchronous machine 4 shown in FIG. 1.

[0037] A special advantage of the electromechanical system with superimposed gearing 1, which system is shown on the basis of the powertrain of a wind power plant, is that wind gusts lead to an additional acceleration of the rotor of the synchronous machine 4 and hence to an increased power production, without the overall system being mechanically overloaded. The system characteristic explained is thus similar to that of wind power plants that are connected to twin-fed asynchronous generators, but it does avoid the drawbacks of the latter, such as the use of carbon brushes, which are subject to wear, as well as the lack of support of the connected power grid.

[0038] FIG. 2 shows the use of an electromechanical system configured according to the present invention with superimposed gearing 1 for transferring torque, rotational energy and power in a powertrain of a processing machine, as it is used, for example, in mining. The system is configured, in particular, for the variable-speed transfer of torque, rotational energy and power. The powertrain according to FIG. 2 has an asynchronous motor, which forms the first machine for energy conversion 2, which is connected directly to the power grid, as well as the processing machine, which is the second machine for energy conversion 3, which is coupled to the main powertrain, according to this configuration. If a corresponding powertrain is used in mining or in other areas with explosion hazard, all parts of the plant, especially the electric motors and generators used, are to be configured as explosion-proof or flameproof parts.

[0039] Compared to the powertrain explained in connection with FIG. 1, identical or at least similar components are used with the exception of the wind rotor, but the direction of the power flow in the powertrain is reversed, namely, from the asynchronous motor 2 via the motor power take-off shaft 5, the superimposed gearing 1 configured as a planetary gearbox 7, the planet carrier 6, an additional gear stage 12 and the drive shaft 17 of the processing machine 3 to the processing machine 3. The advantage of the embodiment shown is that the asynchronous machine 2 operating as a motor can be connected directly to the power grid. While the asynchronous machine 2 is switched to the grid, a low counter-torque is built up at the same time by the drive electronic system 13 in the air gap of the permanently excited synchronous machine, which is the third machine for energy conversion 4 coupled to the powertrain, so that the internal gear 10 configured as the rotor of the synchronous machine 4 is rotated and most of the power introduced by the asynchronous machine 2 into the powertrain is fed in the form of electrical energy into the connected power grid via the synchronous machine 4 and via the drive electronic system 13 thereof. The power released by the asynchronous motor 2 is fed now again nearly completely into the power grid via the synchronous machine 4 especially at the beginning of the start phase. Pulse-like overloads of the powertrain are avoided nearly completely due to a soft build-up of the counter-torque in the synchronous machine 4.

[0040] As soon as the asynchronous machine 2 and the processing machine 3 connected to this via the superimposed gearing 1 as well as via a stepup gearing 12 have reached the operating speed and the powertrain is thus in a quasi-stationary operation, the effect of an overload clutch can be achieved by setting a defined torque in the synchronous machine 4 with the superimposed gearing 1. An overload situation, for example, due to a blockage of the processing machine 3, would bring about an acceleration of the rotor of the synchronous machine 4 and feed again the additional power, which is present in the powertrain and is generated by the asynchronous machine 2, directly into the grid, without the other components of the powertrain being mechanically overloaded. Since only a portion of the power is sent via the drive electronic system 13, this drive electronic system 13 can be adapted corresponding to the power and manufactured in a comparatively cost-effective manner.

[0041] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.