WO2008065234A1 - Inductive component manufacturing method - Google Patents

Abstract

The invention pertains to the manufacture of inductive components and electric energy filters, particularly it relates to a modular inductive component. The method according to the invention makes it possible to manufacture effectively and flexibly various types of inductive components and the compact filters they comprise. Production logistics can be simplified and in addition products can be easily customised with a variety of added features. Production logistics can be simplified and products can be easily customised with a variety of added features. The manufacturing process of this method is also easy to automate.

Description

INDUCTIVE COMPONENT MANUFACTURING METHOD

Method for the manufacture of an inductive component and a modular inductive component as well as a filter and a filter family.

Inductive components, chokes and transformers are used in the storage of energy (choke) and transmission over galvanic separation (transformer) using a magnetic field. Inductive components are comprised of a coil and a magnetic core, of which there may be one or more and which are in direct contact with one another. Voltage applied to the coil produces in the core a magnetic field that is capable of storing energy. The voltage applied to the coil induces voltage within itself (self- induction) as well as any other possible so-called secondary coils connected to the same core, thus transmitting stored energy from the primary coil to the secondary coils. Transformer plates, iron powder, ferrite and amorphic metals, among others, are used as the core material in inductive components. Copper wire, aluminium wire, circuit boards, foil, among others, are used as the coil for inductive components. Inductive components can also be coupled with other types of components, such as resistors and capacitors as well as together with switch components in order to form, for example, filters. In electrical engineering filters are used, for example, to filter electric energy, i.e. components with different frequencies are removed or left as is. Examples of these types of filters include the following: 1) harmonics chokes, which are used to filter the waveform of the mains current; 2) sine filters, which are used to filter the signal in the pulse width modulated and high frequency components of frequency converters into sinusoidal waveform; 3) du/dt filters, which are used to filter pulse width modulated and high slew-rate frequency converter signals into lower slew rate signals; as well as numerous other filters which can be combinations of the above-mentioned filters.

Inductive components and filters are currently designed and manufactured specifically for each application and current. In such cases the design of, for example, a 1-1000A filter family requires a considerable amount of time. Furthermore, production logistics is complicated to organise, as there is an extremely wide range of different designations in production, when each filter requires its own specific subcomponents. It is therefore difficult to control the production process of both low and high output (i.e. large) inductive components simultaneously. In addition, a high output (e.g. 1000A) inductive component is large in size, as the surface area required for cooling is in relation to the total dissipation and the maximum allowable dissipation power density (dissipation per density) is therefore less than that of a smaller component. The current density and dissipation power density values used as component design parameters must then be decreased, which increases the size, price and weight of the component. In addition, the high frequency of a large inductive component (e.g. 1000A) coil, i.e. the AC resistance, will be great, as the high current output requires a large conductor. Conversely, at high frequencies the current only makes use of the conductor surface layer, thus increasing the effective resistance of a thick conductor. For example, Sintermetal Prometheous and Micrometals make chokes based on sinter metal, but they are large, single-piece chokes and high power chokes are not available or the manufacture of such a product would require exceptionally large presses.

In some cases individual E-shaped cores are installed consecutively to form a sort of modular structure. However, such a unit has a single coil, whose form is not optimal.

At lower power outputs, such as in a switched-mode power supply, several inductive components can be mounted on a circuit board side-by-side to form a sort of module. \n such cases it is possible to, for example, divide a large transformer into several smaller transformers to reduce the overall height of the unit. However, this solution is limited to low power outputs, primarily in switched- mode power supplies (typically <5kW).

It can be generally stated that power electronics filters available on the market do not effectively meet the miniaturisation and packaging efficiency currently prevailing in electronics.

The purpose of the invention being presented here is to improve the manufacture or inductive components and the filters comprised of them as well as to increase the compactness of these types of filters. The method of the invention is characterized by what is disclosed in the characterization part of claim 1.

The method according to the invention makes it possible to manufacture effectively and flexibly various types of inductive components and the compact filters they comprise. Production logistics can be simplified and in addition products can be easily customised with a variety of added features. The manufacturing process of this method is also easy to automate.

In the primary embodiment an inductive component and the filter comprised of it are manufactured by coupling smaller inductive components so-called modules in a parallel and/or serial configuration. In this case only the module requires optimisation during the design phase and a product family is quickly grown up by scaling. Logistical benefits are also gained in production with a reduced number of product designations. The core of these modules is made with a "Sintermetal" material, whose excellent mechanical properties allow the transformer core to also be used as the mechanics or part thereof of an inductive component and a filter comprised of a component of this kind. The modules can be designed and manufactured with a variety of, for example, fastening structures or parts for fastening structure, thus making it possible to mechanically couple the modules to one another using the fasteners integrated in the module cores.

In the second embodiment some of the modules are also fitted with electronics, thus making it possible to implement the method in the manufacture of a compact power electronics converter.

In the third embodiment electronics is integrated inside the main inductive modules.

The invention is described below in greater detail, with reference to suggestive drawings, where:

Figure 1 shows the graphic symbol of a choke (1), which has two terminals (2) and (3) and a core (4). Figure 2 shows the graphic symbol of a filter (5), which has a choke (6) and capacitor (7) as well as an input (8) and output port (9).

Figure 3 shows a three-phase filter (10), which has chokes (11) and capacitors (12).

Figure 4 has a power electronics converter (13), whose input (14) is fitted with a filter (15) and output (16) is fitted with a filter (17), and whose output filter (17) has connections to the converter (13) intermediate circuit + (18) and - (19) poles.

Figure 5 shows a du/dt filter input (20) and output voltage (21) curve as well as the sine filter input (22) and output voltage (23) curve.

Figure 6 shows the three-phase choke (24), which has coils (25) and a common core (26).

Figure 7 shows the three-phase choke (27), which has coils (28) around separate cores (29).

Figure 8 shows a choke (30), which has an input terminal (32) and output terminal (33) and which is comprised of one or more modules (31) and terminals connection (36) and mechanics connection (35).

Figure 9 shows the modules (39) in a three-dimensional arrangement (37).

Figure 10 shows a cooling gap (41) between the modules (40)

Figure 11 shows a cooling module (43) within the modules (42).

Figure 12 shows suggestively a rotationally symmetrical cross-section of a module (44) comprised of a coil (45), core (46) and insulation (47). Figure 13 shows a one-phase core (48), which has a center pin (49), corner pin (50) and mounting hole (51).

Figure 14 shows a three-phase core (52), which has a pin (53) and mounting hole (54).

Figure 15 shows a coil (55), an insulator half (56) and a core half (57).

Figure 16 shows an assembled module (58), which has an insulator mount (59), a module assembly coupled with insulator connectors (61) and a modular choke (62), which is comprised of a connector (63) and a capacitor (64).

Figure 17 shows a modular structure (65), which has a mounting element (66)

Figure 18 shows the sinter metal core (67), which is comprised of several parts (70), (69) and (68), and which has a mounting element.

Figure 1 shows the symbol for the simplest inductive component, the choke. The choke (1), or inductance, is comprised of the coil, which has two terminals, or poles (2) and (3). In most cases the choke (1) also has a core (4) made of a magnetic material, such as ferrite or iron. The choke stores energy in its magnetic field and this energy can be added or discharged via the terminals. More complex inductive components, such as transformers, may have even several coils, thus allowing energy to be transferred between the terminals of the different coils. This invention also comprehends these types of complex inductive components. In many cases the core (4) symbol is not shown.

A so-called filter (5) can be created, for example, by connecting the choke (6) to the capacitor (7) as shown in Figure 2. This type of filter can be used, for example, to prevent high frequency interferences from moving from the input port (8) to the output port (9).

In power electronics, particularly at higher power outputs (e.g. >10kW) it is typical to use a three-phase system. A three-phase system filter (10) is comprised of chokes (11) and capacitors (12) for each phase. Figure 3 shows the capacitors

(12) coupled using a so-called star connection, but they may be connected in other configurations, such as a delta connection. Furthermore, the number of filter phases can also be something other than 1 or 3. The capacitors (12) pictured can be physically comprised of several separate capacitors.

Figure 4 shows a power electronics converter (18), which is connected to the input (14) via the filter (15) and to the output (16) via the filter (17). The converter could be, for example, a rectifier, inverter or frequency converter, where the input (14) would be mains power and the output (16) would be connected to an electric motor with a cable. Alternatively, the input (14) could be connected to a generator and the output (16) could be connected to the mains power. The output (16) filter (17) is connected via capacitors to the + (18) and - (19) poles of the converter's

(13) intermediate circuit. Thus, energy can be effectively and optimally transferred between the input (14), output (16) and converter (13). It is also possible to effectively dampen electromagnetic interferences. The connections shown in Figure 4 are examples - filters can be configured in several different ways depending on the application. In addition connections from the filter (17) to the converter's (13) intermediate circuit + (18) and - (19) poles can be made with means other than capacitors. Likewise, the converter (13) could also be one- phase.

Figure 5 shows examples of filtered curves in motor drive applications. The so- called du/dt filter dampens the input vo\tage (20) slew rate (typically 5kV/us) into a slower output voltage (21) (typically 1kV/us). This kind of filtering reduces motor overvoltages and, in turn, reduces insulator damages and bearing faults when using long motor cables. In the second example pulse width modulated input voltage (22) is filtered into sinusoidal output voltage (23). This improves the motor's efficiency and reduces the disturbing noise level. Harmonic current filtering can also be mentioned in addition to these applications. These types of filters can also be coupled together to form, for example, an LCL filter, which is used to transmit energy from the frequency converter to mains power. The LCL filter choke degrees can be comprised of one or three-phase chokes. In addition to the above-mentioned filters, the invention can also be adapted for use in the manufacture of transformers, for example, if the frequency converter output voltage is to be increased to a higher level.

Figure 6 shows one way of making a three-phase choke (24). In this case the three coils (25) of the choke are coiled on a common, three-leg core (26). Thus, the three-phase choke forms a mechanically solid structure. The structure can also be used to advantage the three-phase system property, wherein the sum of operating currents is zero, thus resulting in a decrease in the total amount of core material used, where each coil's magnetic flux can run through two other coils and individual flux returns are not required for each coil. Correspondingly, a problem with this structure is that it does not have significant inductance against nonfunctional parasitic noise currents, which would like to be often also filtered.

Figure 7 shows another way to make a three-phase choke (27). In this example each phase is coiled (28) on its own core (29). This alternative requires slightly more core material, because each phase has its own magnetic flux return route. However, this type of configuration provides substantial damping also of nonfunctional aka parasitic noise currents.

In Figure 8 the choke (30) is formed by coupling smaller choke modules (31) together. In its simplest form this can be done by connecting the input terminals (32) of parallel-connection modules to each other and, correspondingly connecting the output terminals (33) to each other, using an appropriate connection method (36), such as soldering, screwing, riveting or another generally known method. Likewise, the mechanics of the choke modules (31) is connected to each other (35), using an appropriate connection method. This makes it possible to quickly design and manufacture a choke for different current values, using, for example, tested and optimised base modules. There can be one or more types of these base modules in a choke.

Figure 9 shows a six module (39) three-dimensional arrangement (37). The modules could be coupled together in several different ways. For example, all the modules could be connected electrically in a parallel, thus forming a single high current module. At the other extreme, the modules would not be electrically connected to one another, thus forming a unit of six low current chokes. In practice a more probable connection might be to always connect two modules electrically in a parallel configuration in order to form a three-phase choke.

It is therefore essential that the mechanical structure of the core of the individual modules also forms the mechanical structure of the modular inductive component. In other words, the assembly process comprehends the mechanical interconnection of all modules and, where electrical function is concerned, the proper electrical interconnection of the proper modules. This type of assembly process is effective and flexible. Alternatively, assembly can be done in phases, so that the assembly and apossible testing of all the modules required for the modular choke are done first, and only then the modular choke itself is assembled, or that also the modules are physically assembled only during the assembly of the modular choke.

The modular structure also has other advantages. For example, because the current of a single module is lower than that of the entire modular choke, the coil wire used in the module can be designed very thin compared to the combined coil surface area of parallel-connected modules. This reduces the coils' high frequency resistance or AC resistance, which reduces losses.

The module can also be configured for different voltages (% of Unom), for example, by connecting the coil parts in a parallel or serial configuration. This approach can be used, for example, when configuring the module for 400VAC or 690VAC.

The invention method makes it possible to integrate multiple filter's, such as an LCL filter, filter degrees to form a single mechanical unit.

Furthermore, because it is possible to leave small gaps at suitable points between modules for air circulation as shown in Figure 10, the total surface area of a choke comprised of modules can be made considerably larger than that of a conventional choke, whereupon a higher density of current and dissipation power can be used in design and, in turn, a more economical filter can be achieved. Another alternative for enhancing cooling is to use specially designed cooling modules as shown in Figure 11. These may utilise, for example, liquid, Peltier or "phase change" cooling. Cooling structures, such as liquid cooling ducts, could also be directly integrated in the choke modules. For example, different types of cooling structures, such as cooling ribs and liquid cooling ducts, can be designed into the modules.

In addition to or instead of the cooling module, a module being integrated in the module unit can also be a capacitor module or electronics module, particularly a module containing power electronics connections.

Figure 12 shows a rotationally symmetrical cross-section of a module (44) comprised of a core (46) (or parts of a core), coil (45) and insulation (47). The insulation can be in the coil or core, it could be a separate part, such as a coil former, or in several of these parts. The module may also have connectors to hold it together and couple it to other modules, filter parts or external parts. For example, the core halves are held together with claw-like clips found in the insulated coil former or, alternatively, the core halves can be pressed against one another using bolt(s) or some other generally accepted method, such as lacquering, gluing, pressing or welding.

An effective core material is sinter metal. It is based on a pressed and sintered metal powder. Sinter meta) can be pressed into the desired form and the forms being manufactured can be extremely detailed, thus allowing power electronics, cooling ribs and liquid cooling to be integrated into the module. In this case the choke/inductive component itself functions as a cooling element. Another alternative core material is iron powder, which is made of pressed magnetic powder.

Figure 13 shows one economical form of the module core (48). The exterior form of the module is square, which makes the modular choke compact. However, the module's center pin (49) is round, which, in turn, is the optimal shape in terms of minimising coil resistance and coil losses. Other geometric forms than those mentioned above can also be used. The corner pins (50) leave the coil exposed, which enhances cooling. Each corner pin (50) also has a mounting hole (51). Because the module core includes through holes for mechanical coupling, the module cores can be pressed (screwed) tightly into place using nuts and a threaded bar. This type of structure reinforces itself. The coils can be coupled to one another, for example, by using threaded bars to conduct the current. Modules can be stacked and fastened using, for example, threaded pins and nuts, other connectors, gluing or welding.

The module core's geometry can be optimised for the sinter metal process. For example, its surface area and height can be made optimal for the process. In addition the module core can consist of several different magnetic materials. For example, it is possible to use a more expensive material with high saturation flux density and low dissipation properties, such as amorphic iron, for the core center pin, and sinter metal elsewhere, due to its excellent mechanical properties. This type of so-called composite core has a superior price/performance ratio than a single-material core would.

Figure 14 shows a three-phase module core. The pins (53) are round and the structure has mounting holes (54). Ready-to-use modules can be retrofitted to make the desired configuration, such as one-phase or three-phase.

The core parts can be halves, such as shown in Figures 13 and 14, or sub-pieces of a half, such as quarter pieces. The core can also be comprised of sectoral sections. Connecting superimposed core parts in an overlapping manner will achieve a robust structure. Air circulation and cooling can be improved by leaving a small gap between sections. The module core halves can also be comprised of various superimposed projections, thus reducing the press area required in the sinter metal process. Conversely, the surface of the core half can be designed so that various air gaps are left between the module core halves during the module assembly phase, e.g. the mutual alignment of the two module halves forms an air gap. Another possibility is that the module halves slide partially into one another. The core halves can be designed so that they slide partially inside one another, thus achieving an adjustable air gap. They can also be designed in such a way that by rotating the square core half 90 degrees against the other half will achieve a variable air gap. It may be appropriate to use several different modules in order to create a wide choke family. The most important thing is that the module dimensions, coil aperture and core cross-section ratios are such that the module's material costs are kept to a minimum and production logistics for the entire choke family is optimised. The risers necessary to form air gaps can be integrated directly in the comer pins using plates inserted in the press mould.

Figure 15 shows the module structural parts: coil (55), insulation (56) and core (57).

Figure 16 shows an assembled module (58), whose insulator section has a mounting structure (59). This structure is used to couple two modules (60) together, thus forming a conductor channel (61) between them. The coil ends of modules in the modular choke (62) can be run to the connector (63) along the conductor channel. In other words, the coil ends can be run along the formed conductor channels to the connection point. Another alternative for the electrical connection of modules is to use separate line bars, to which the coil ends are connected. A line bar can also be run along the conductor channel. It can also be appropriate to fit the structure with various end plates and partition plates between the modules in order to form mounting structures required for the later installation of a ready-fitted filter. These can be freely configured for vertical and/or horizontal mounting.

The module core can be made to fulfil protective insulation requirements, thus the entire modular component is protective insulated and external housing is not needed.

Other electronics, particularly power electronics, can also be integrated into the same mechanical entity with the filter, thus resulting in a compact power electronic unit for example for supplying energy to mains. Even a generator or motor can be integrated into this entity. Electronics can be integrated inside the core half or even within a section of it. For example, a cavity for the installation of other electronics can be left in the sinter metal core. Figure 17 shows how different mounting elements (66) can be integrated into the modular structure (65) for use in such applications as wall mounting. Although the mounting shown in the figure uses a flange (66), the mounting element could also be another generally known mounting method, such as a DIN rail mount. Mounting structures can also be made either entirely or partially in the core module.

It may be appropriate that the sinter metal core used in the manufacture of modules be comprised of several parts. For example, the size of the press may be limited in such a way that the desired core cannot be manufactured in one stroke. Figure 18 shows this type of core (67). It is made using parts (68), (69) and (70). Parts (68) and (69) are connected to each other by, for example, gluing, soldering or another generally known method. Parts (70) and (69) are connected to each other using also amounting element (71), which is used to join parts (70) and (69) to each other.

Claims

1. Method for the manufacture of an N-phase modular inductive component of modules by joining of module mechanics and module coils together, characterized in that the modules' mechanics are joined to form a single mechanical connection, whereas the coils are joined to form N electrical connections.

2. A modular inductive component according to claim 1 whose modules are comprised of a core, a coil and an insulation, characterized in that a sinter metal material is used as the core material.

3. A modular inductive component according to claim 1 whose modules are comprised of a core, a coil and an insulation, characterized in that a sinter metal material and some other magnetic material is used as the core material.

4. A modular inductive component according to claim 3 whose modules are comprised of a core, a coil and an insulation, characterized in that a material possessing a higher flux density and/or lower dissipation is used in the center pin.

5. A modular power electronics device according to claim 1 , characterized in that the modules are chokes, capacitors or electronic.

6. A modu)ar inductive component according to claim 2 whose modules are comprised of a core, a coil and an insulation, characterized in that electronics have been integrated into the core.

7. A modular inductive component according to claim 1 whose modules are comprised of a core, a coil and an insulation, characterized in that a conductor channel is formed by the insulation.

8. A modular inductive component according to claim 1 whose modules are comprised of a core, a coil and an insulation, characterized in that liquid cooling ducts have been integrated into the core. 5

9. A modular inductive component according to claim 1 whose modules are comprised of a core, a coil and insulation, characterized in that the modules are protective insulated.

10 10. A modular inductive component according to claim 1 , characterized in that said component can be configured from one-phase to three-phase and vice versa.