• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A rotating structure of an electromechanical system (1) is surrounded by a closed ferromagnetic structure (13) that increases the electrical impedance to shaft currents and reduces the wear of bearings caused by electrical currents passing through them.
    公开号:BE1019355A3
    申请号:E201000331
    申请日:2010-05-31
    公开日:2012-06-05
    发明作者:Sande Hans Vande
    申请人:Atlas Copco Airpower Nv；
    IPC主号:
    专利说明:

    Electromechanical system and method for manufacturing such electromechanical system.
    This invention relates to electromechanical systems that contain, for example, frequency-controlled AC machines or large-network-connected AC machines.
    The use of power electronic energy converters for frequency control of electrical machines is widespread.
    The majority of low voltage and medium voltage power electronic converters used in the industry are based on voltage source inverter technology. In voltage source inverters, the sinusoidal alternating mains voltage is first rectified into an approximately constant voltage, before being converted again into an alternating voltage with a certain amplitude and frequency. The latter is done by using semiconductor switches. Consequently, the output voltage can only be a discrete number of values. .take. A sinusoidal. . outgoing voltage can only be obtained in an average way, by switching at a much higher frequency than the desired basic frequency and according to a certain switching pattern. In this context, modulation techniques such as pulse width modulation (PWM) or space vector modulation (SVM) are often encountered.
    Although the advent of frequency control has unleashed a revolution in electrical drive technology and automation, it has also introduced a number of additional problems such as harmonic currents in the network, accelerated aging of electrical insulation, grounding problems, electromagnetic interference, shaft and bearing currents, and Others. This description only focuses on shaft and bearing flows.
    In perfectly balanced multi-phase electrical systems, the sum of all phase voltages and phase currents equals zero at any time. At the output of most voltage source inverters it is only possible to satisfy this condition in an average way: the instantaneous sum generally differs from zero. A so-called common mode voltage is generated by the voltage source inverter. The common mode voltage, being the difference between the average voltage and the earthing voltage, changes constantly during switching, but its average value is zero.
    Just like the phase voltages, the common mode voltage can only assume a discrete number of values. Very short voltage transitions occur during switching. Short switching times are important to keep the switching losses to a minimum. However, in modern power electronic energy converters that use, for example, IGBT semiconductor switches, the rate of voltage change can be such that capacitive currents can flow into the machine. Consequently, high-frequency common mode currents can flow from the copper coils through the electrical capacity of the insulation materials to a stack of grounded stator blades. Similarly, another fraction of the common mode current can capacitively pass through the air gap to the rotor and flow back to earth through the bearings of both the electrical machine and the installation that is mechanically coupled to it. Current can flow within a bearing by means of conduction, capacitive coupling or even electrical breakdown of the bearing lubricants. This explains a first source of bearing currents.
    Common mode currents that flow to the ground through the insulation system and the stator frame cause a net circulating magnetic flux in the core of the electrical machine. This flux, in turn, can induce significant high-frequency axial axis stresses and, consequently, also additional axis and bearing currents. This explains a second source of bearing currents.
    In fact, axial axis stresses as a source of bearing currents have been known long before the advent of frequency control. In fact, each electrical machine has a residual magnetic asymmetry of the can package. Consequently, there is always a certain alternating scattering flux coupled to the shaft, which causes shaft stresses. The big difference with frequency-controlled machines is the considerably lower frequency of this phenomenon. Induced axial stresses of this type are only of greater importance in larger electrical machines, but form a third. source of. bearing currents.
    As previously indicated, the majority of low voltage and medium voltage power electronic energy converters used in the industry are based on voltage source inverter technology. In addition, there is an important class of power electronic energy converters based on power source inverter technology. Common mode voltages are also present in current source inverters, but their harmonic content is considerably smaller than in voltage source inverters. However, axis voltages and common mode currents have also been observed in a number of applications where current source inverters were used.
    Regardless of the type of power electronic inverter that is used or the remaining magnetic anisotropy of the electrical machine, dirty, damage to the bearings of electrical machines and the mechanically coupled installation has already been assigned to shaft and bearing currents in many industrial applications. Engine and generator builders are aware of common mode phenomena and have identified a number of solutions for solving or reducing the following problems. However, the phenomenon is often difficult to predict, experts must be approached, and solutions may depend on the specific application, the power electronic components and the electrical machine construction. System builders who use electrical machines in their applications are therefore required to take a number of remedial measures, regardless of the type of drive or electrical machine.
    One measure can be the use of a perfectly insulated coupling between the electrical machine and the installation that is mechanically coupled to it. Sometimes this is not possible, for example in systems where a gearbox connects the driving machine and the driven machine. Even when it is possible, it does not prevent ash flows from occurring in the electrical machine itself.
    Another measure is the mounting of an axle earthing brush around the drive shaft, to divert all ash flows directly to the ground. This requires an electrical contact between a rotating and a non-rotating part, which can be subject to wear and therefore maintenance. Moreover, it does not prevent ash flows from being generated. The latter can be problematic, since shaft currents derived in this way can still cause grounding problems and electromagnetic interference if not executed properly.
    It is a fundamentally better strategy to tackle the cause of axes bearing currents than to direct axes away from the bearings when they are already there. To do that, one must try to increase the impedance for common mode currents, without affecting the impedance for normal operational currents. Various solutions have already been described for this, such as sine wave filters, galvanically isolated transformers, common mode transformers and common mode coils. These components are always physically mounted somewhere between the power electronic energy converter and the electrical machine. They all represent a certain cost, level of complexity and size.
    A simple magnetically permeable ring that forms a common mode coil and is placed around machine cables, where the ring forms an inductance for common mode currents but hardly forms an impedance for perfectly balanced multiphase currents, is already known. This technique is well known in the field of electric drive systems.
    The present invention aims at overcoming one or more problems and disadvantages related to existing electromagnetic systems and more particularly the problems related to the occurrence of shaft and bearing currents.
    With this in mind, the invention relates to an electromechanical system comprising an electrical subsystem and a mechanical subsystem, wherein the electrical subsystem and the mechanical subsystem are mechanically coupled, wherein at least one of the aforementioned electrical subsystem and said mechanical subsystem have a rotating structure, wherein, according to the invention, a closed ferromagnetic structure encloses the aforementioned rotating structure.
    Compared with the classical annular common mode coil around the machine cables, the use of a ferromagnetic structure around a rotating structure of an electromechanical system has the advantage that low frequency common mode axis currents are also reduced due to the remaining anisotropy of the can package.
    An additional advantage is that one should not take into account the electromagnetic shielding of the machine cables, which should normally be used in frequency-driven electrical machines but not have to go through the opening of the common mode coil.
    Another advantage of the electromechanical system according to the invention is that the ferromagnetic structure can be mounted in a contactless manner, with which friction losses are avoided and, in addition, that it is a very inexpensive solution.
    The invention also relates to a method for mounting an electromechanical system, the method comprising the following steps: - providing an electrical subsystem; - providing a mechanical subsystem; - mechanically coupling said electrical subsystem to said mechanical subsystem, wherein at least one of said electrical subsystem and said mechanical subsystem comprises a rotating structure; and - mounting a closed ferromagnetic structure with a continuous inner opening over the rotating structure.
    For the purpose of better illustrating the features of the invention, a description is given below without any limiting character of some preferred embodiments of an electromechanical system according to the invention and of a method for mounting an electromechanical system, with reference to the accompanying drawings, in which: figure 1 represents a schematic overview of a known electromechanical system; Figure 2 represents a schematic overview of a known electromechanical system provided with a classical annular common mode coil; Figure 3 represents an electrical subsystem of an electromechanical system according to the invention; Figure 4 represents a ferromagnetic structure as indicated by arrow F4 in Figure 3; Figure 5 represents a variant of a ferromagnetic structure of Figure 4; Figure 6 represents a variant of Figure 3; Figure 7 represents a schematic overview of a mechanical subsystem according to the invention; figure 8 represents a schematic overview, on a larger scale, of a part of a mechanical subsystem of an electromechanical system according to the invention; Figure 9 represents a 3D image of a closed ferromagnetic structure that encloses an axis; Figure 10 represents a variant of Figure 9; Figure 11 represents a 3D image of a closed ferromagnetic structure that can be used in an electromechanical system according to the invention; Figure 12 represents a variant of Figure 11; Figure 13 represents another variant of Figure 9, while the closed ferromagnetic structure is mounted; Figure 14 represents a motor that drives a compressor via a shaft provided with a closed ferromagnetic structure according to the invention; Figure 15 represents a motor that drives a pump via a shaft provided with a closed ferromagnetic structure according to the invention; Figure 16 represents a motor that drives a fan via a shaft provided with a closed ferromagnetic structure according to the invention; Figure 17 represents a motor that drives a crane or lift via a shaft provided with a closed ferromagnetic structure according to the invention; Figure 18 represents a generator driven by a gas turbine or steam turbine via a shaft provided with a closed ferromagnetic structure according to the invention; Figure 19 represents a generator driven by a windmill or water turbine via a shaft provided with a closed ferromagnetic structure according to the invention; Figure 20 represents a generator driven by a motor or combustion engine via a shaft provided with a closed ferromagnetic structure according to the invention;
    Figure 1 shows a conventional electromechanical system 1 in the form of a drive comprising an electrical subsystem 2 and a mechanical subsystem 3. The electrical subsystem 2 is electrically coupled to an electricity network 4 via an electrical power converter 5. The electrical subsystem 2 is mechanically coupled to the mechanical subsystem 3.
    In this case, both the electrical subsystem 2 and the mechanical subsystem 3 comprise a rotating structure 6. One or more of these rotating structures 6 is supported by one or more bearings which are not shown in Figure 1.
    Figure 2 shows a conventional variant of Figure 1, in which an annular common mode coil 7 is mounted around the cables that connect the electrical power converter 5 to the electrical subsystem 2.
    Figure 3 shows, on a larger scale, an electrical subsystem 2 of an electromechanical system 1 according to the invention, wherein the electrical subsystem 2 comprises, for example, a rotating electric motor or generator consisting of a stator 8 with a housing 9 and a rotor 10 with a shaft 11, wherein the rotor 10 is supported by bearings in the stator housing 9 by means of bearings 12 and thus forms the aforementioned rotating structure 6.
    According to the invention, a closed ferromagnetic structure 13 encloses the aforementioned rotating structure 6. Figure 4 shows a schematic overview of a closed ferromagnetic structure 13 that can be used for that purpose. Such a closed ferromagnetic structure 13 is preferably constructed as a ring of highly permeable ferromagnetic material that has a high saturation flux density.
    In the example of Figure 3, the ferromagnetic structure 13 is located between the bearings 12 of the electrical subsystem 2, and more particularly next to the bearing 12 on the side of the electrical subsystem 2 which is coupled to the mechanical subsystem 3 which is not shown is in Figure 3.
    According to the invention, the aforementioned closed ferromagnetic structure 13 can take various forms, as long as it is provided with a continuous inner opening 14 which allows to fasten the closed ferromagnetic structure 13 around any rotating structure 6 of the aforementioned electromechanical system 1. This means that the shape of the closed ferromagnetic structure 13 must be homotopic equivalent to the shape of a ring.
    Figure 5 shows, for example, such another embodiment of a closed ferromagnetic structure 13 according to the invention, wherein the closed ferromagnetic structure 13 is manufactured in the form of an a-hexagonal core of highly permeable material with a high saturation flux density.
    In the example of Figure 6, the closed ferromagnetic structure 13 is located outside the bearings 12 of the electrical subsystem 2, and more particularly on the side of the electrical subsystem 2 which is coupled to the mechanical subsystem 3 which is not shown in Figure 6.
    Figure 7 shows a schematic overview of a mechanical subsystem 3 of an electromechanical system 1 according to the invention, wherein the mechanical subsystem 3 is provided with a rotating structure 6 which is supported by bearings 12. This mechanical subsystem 3 further comprises a closed ferromagnetic structure 13 which encloses at least a part of the rotating structure 6, in this case between the bearings 12 of the mechanical subsystem 3.
    Figure 8 shows, on a larger scale, a part 15 of a mechanical subsystem 3, which in this case contains a mechanical coupling 16 connecting two shafts 11 to each other by means of two radial flanges 17, the part 15 of the mechanical subsystem 3 is free of bearings 12 and wherein the part 15 of the mechanical subsystem 3 is preferably axially mounted between the flanges 17 and at an axial distance therefrom.
    The closed ferromagnetic structure 13 can either be attached to a rotating structure 6 of the electromechanical system 1 and thus rotate with that rotating structure 6 as shown in Fig. 9, or the closed ferromagnetic structure 13 can be attached around a rotating structure 6 of an electromechanical system 1 so that it does not rotate with this rotating structure 6, which is represented by figure 10.
    In order to be able to attach the closed ferromagnetic structure 13 to the relevant rotating structure 6, the closed ferromagnetic structure 13 preferably comprises a continuous inner opening 14 whose inner diameter is slightly smaller or equal to the outer diameter of the part of the respective rotating structure 6 to which it closed ferromagnetic structure 13 is attached.
    In the case that the closed ferromagnetic structure 13 is mounted about the axis 11, the closed ferromagnetic structure 13, for example in the form of a ring, contains a through-going inner opening 14 with a diameter larger than the outer diameter of the part of the rotating structure 6 around which the closed ferromagnetic structure 13 is provided.
    Each common mode current through any rotating structure 6 of the electromechanical system 1 generates a magnetic flux around this rotating structure 6. The inductance of the closed ferromagnetic structure 13 is equal to the ratio of that magnetic flux to the common mode current. If the rotating structure 6 is not enclosed by the closed ferromagnetic structure 13, the inductance is small. However, by attaching the closed ferromagnetic structure 13, the inductance can be increased considerably because its value is proportional to the relative permeability of the closed ferromagnetic structure 13, which is easily a factor of 1000 higher than that of air.
    In addition, the inductance is proportional to the area of the axial cross-section of the closed ferromagnetic structure 13 and inversely proportional to the circumference of the closed ferromagnetic structure 13. For this reason, it is best that the closed ferromagnetic structure 13 make the rotating structure 6 as narrow as as possible. If the rotor dynamics of the rotating structure 6 is of no importance, the closed ferromagnetic structure 13 can be attached to any rotating structure 6, as previously explained.
    Since the aforementioned common mode current varies over time, the magnetic flux also varies over time. Consequently, the closed ferromagnetic structure 13 is subject to time-varying magnetic fluxes, and measures must be taken to limit the resulting eddy current losses.
    For this reason, a ferrite core or soft-magnetic composite powder core with a low electrical conductivity is preferably used. The invention is of course not limited to this, since various options are available. The closed ferromagnetic structure 13 can be manufactured, for example, as a stack of fully enclosed thin slats as shown in Figure 11, in a similar manner to the laminated core of most electric motors.
    Alternatively, one may wrap the closed ferromagnetic structure 13 on the circumference as shown in Figure 12. In this case, one may use even more advanced ferromagnetic materials, such as amorphous or nanocrystalline materials, or soft-magnetic metal fiber composites.
    In order to facilitate the assembly of the closed ferromagnetic structure 13 in an application, it is permitted to manufacture it from a plurality of ferromagnetic components 18 as shown in Figure 13. The necessary condition is that the closed magnetic circuit does not show any air gaps after assembly, since these air gaps significantly reduce the inductance and current limiting capability of the closed ferromagnetic structure 13.
    It is clear that, according to the invention, the closed ferromagnetic structure 13 can be provided around any rotating structure 6 of an electromechanical system 1, such rotating structures 6 being part of an electrical subsystem 2 and / or a mechanical subsystem 3. Of course, such ferromagnetic structure 13 can also be provided around more than one rotating structure 6 and can only enclose a part of the rotating structure 6, or the rotating structure 6 as a whole.
    It is clear that the rotating structure 6 can be supported by bearings, however, it is also possible that the rotating structure 6 around which the closed ferromagnetic structure 13 is provided is free of bearings 12, since such rotating structure 6 can be coupled to other structures supported by bearings.
    In the event that the aforementioned electrical subsystem 2 is made in the form of an electric motor coupled to an electricity network 4 via a direct connection, a filter, a transformer, a power electronic energy conversion system or a combination of two or more of these, the mechanical subsystem 3 consists of different types of loads including a compressor 19 as shown in Figure 14, a pump 20 as shown in Figure 15, a fan 21 as shown in Figure 16, a lift or crane 22 as shown in Figure 17, etc.
    Conversely, if the electrical subsystem 2 is a generator, then the mechanical subsystem 3 is a driving machine, including a gas turbine or steam turbine 23 as shown in Figure 18, a windmill or water turbine 24 as shown in Figure 19, an engine or internal combustion engine 25 such as shown in Figure 20, etc.
    The invention is in no way limited to the embodiments described by way of example and shown in the figures, since an electromechanical system 1 according to the invention can be made in all shapes and dimensions without departing from the scope of the invention. The method according to the invention for manufacturing an electromechanical system 1 can also be realized in various ways and yet remain within the scope of the invention.
    权利要求:
    Claims (29)
    [1]
    An electromechanical system comprising an electrical subsystem (2) and a mechanical subsystem (3), wherein the electrical subsystem (2) and the mechanical subsystem (3) are mechanically coupled, wherein at least the electrical subsystem (2) or the mechanical subsystem (3) comprises a rotating structure (6), characterized in that a closed ferromagnetic structure encloses the aforementioned rotating structure (6).
    [2]
    Electromechanical system according to claim 1, characterized in that the electrical subsystem (2) is directly electrically coupled to an electricity network (4).
    [3]
    Electromechanical system according to claim 1, characterized in that the electrical subsystem (2) is electrically coupled to an electricity network (4) via passive electrical components, such as transformers and filters.
    [4]
    The electromechanical system according to claim 1, characterized in that the electrical subsystem (2) is electrically coupled to an electricity network (4) via a power electronic energy converter.
    [5]
    Electromechanical system according to claim 1, characterized in that the electrical subsystem (2) comprises an electric motor.
    [6]
    Electromechanical system according to claim 1, characterized in that the electrical subsystem (2) comprises an electrical generator.
    [7]
    Electromechanical system according to claim 1, characterized in that the mechanical subsystem (3) contains a compressor.
    [8]
    Electromechanical system according to claim 1, characterized in that the mechanical subsystem (3) comprises a pump (20).
    [9]
    Electromechanical system according to claim 1, characterized in that the mechanical subsystem (3) comprises a fan (21).
    [10]
    Electromechanical system according to claim 1, characterized in that the mechanical subsystem (3) comprises a turbine (23).
    [11]
    Electromechanical system according to claim 1, characterized in that the mechanical subsystem (3) comprises a windmill (24).
    [12]
    Electromechanical system according to claim 1, characterized in that the mechanical subsystem (3) comprises a combustion engine (25).
    [13]
    Electromechanical system according to claim 1, characterized in that the mechanical subsystem (3) comprises a lift (22),
    [14]
    Electromechanical system according to claim 1, characterized in that the closed ferromagnetic structure (13) is connected to the rotating structure (6).
    [15]
    The electromechanical system according to claim 1, characterized in that the closed ferromagnetic structure (13) is connected to a non-rotating part of the electrical subsystem (2).
    [16]
    The electromechanical system according to claim 1, characterized in that the closed ferromagnetic structure (13) is connected to a non-rotating part of the mechanical subsystem (3).
    [17]
    The electromechanical system according to claim 1, characterized in that the electromechanical system (1) further comprises an external non-rotating holder to which the closed ferromagnetic structure (13) is connected.
    [18]
    The electromechanical system according to claim 1, characterized in that the closed ferromagnetic structure (13) is composed of a plurality of interconnected parts.
    [19]
    The electromechanical system according to claim 1, characterized in that the closed ferromagnetic structure (13) has a rotationally symmetrical shape.
    [20]
    The electromechanical system according to claim 1, characterized in that the closed ferromagnetic structure (13) comprises a stack of thin slats that are electrically insulated from each other.
    [21]
    The electromechanical system according to claim 1, characterized in that the closed ferromagnetic structure (13) is composed of wound flat ribbon.
    [22]
    The electromechanical system according to claim 1, characterized in that the closed ferromagnetic structure (13) is composed of a magnetic fiber matrix composite.
    [23]
    Electromechanical system according to claim 1, characterized in that the closed ferromagnetic structure (13) is composed of a ferrite.
    [24]
    The electromechanical system according to claim 1, characterized in that the closed ferromagnetic structure (13) is composed of a soft-magnetic composite powder.
    [25]
    Electromechanical system according to claim 1, characterized in that the closed ferromagnetic structure (13) is made up of an amorphous or nano-crystalline material.
    [26]
    Method for constructing an electromechanical system, characterized in that the method comprises the following steps: - providing an electrical subsystem (2); - providing a mechanical subsystem (3); - mechanically coupling the electrical subsystem (2) to the mechanical subsystem (3), wherein at least the electrical subsystem (2) or the mechanical subsystem (3) comprises a rotating structure (6); and - mounting a closed ferromagnetic structure (13) with a continuous inner opening over the rotating structure (6).
    [27]
    Method according to claim 26, characterized in that the closed ferromagnetic structure (13) is split into separate ferromagnetic parts that are pressed against each other after the closed ferromagnetic structure (13) is attached over the rotating structure (6).
    [28]
    Method according to claim 26, characterized in that the method comprises the step of attaching the closed ferromagnetic structure (13) to the rotating structure (6).
    [29]
    A method according to claim 26, characterized in that the method comprises the step of attaching the closed ferromagnetic structure (13) to a non-rotating part of the electromechanical system (1).
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    同族专利:
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    引用文献:
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    US6984906B1|2000-07-13|2006-01-10|General Electric Company|Bearing current reduction assembly|
    DE102005012656A1|2005-03-18|2006-06-14|Siemens Ag|Inverter fed AC machine has core around drive shaft at drive end and further cores around shaft within the machine|
    US20090273251A1|2005-09-30|2009-11-05|Ralf Cordes|Synchronous Machine|
    FR2933544A1|2008-07-03|2010-01-08|Alstom Transport Sa|Machine e.g. alternating current asynchronous electrical motor, for rail transit car, has fixed rim fixed to carcass outside extension of exterior space of bearings, and rotating rim fixed to shaft remote from internal ring of bearings|
    法律状态:
    2013-11-30| RE| Patent lapsed|Effective date: 20130531 |
    优先权:
    申请号 | 申请日 | 专利标题
    US32782610P| true| 2010-04-26|2010-04-26|
    US32782610|2010-04-26|
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