DE102008031296A1 - Inductor device for e.g. output-sinusoidal filter of frequency converter, has three coils arranged on core from magnetic material, and another core arranged above three coils and forming single inductor acting as longitudinal inductance - Google Patents

Abstract

The device (11) has three coils (29) arranged on a core (27) from magnetic material. Another core (31) is arranged above the three coils (29) and forms a single inductor acting as longitudinal inductance. The core (27) has a high permeability and exhibits a small air gap. The core (31) has a larger air gap (33). The core (27) has horseshoe or U-shaped side piece embracing the coils with an open side and coupled to a section of the core (27). The component corresponds functionally to a series connection of a current-compensated inductor and inductor arranged in voltage-conducting phasing lines. An independent claim is also included for a filter circuit i.e. three-phase filter circuit, for limitation of a slew rate and voltages between voltage-conducting lines and earth potential, comprising capacitors.

Description

The The present invention relates to a choke coil device for a filter circuit, in particular for an output sine filter an inverter included in a frequency converter, wherein the reactor means is adapted to functionally a series connection of a current-compensated throttle with one each arranged in each live phase line, corresponds to acting as a longitudinal inductance choke. The invention further relates to a use of such a choke coil device in a filter circuit and finally a filter circuit with such a choke coil device.

Especially In drive technology, frequency converters are used for voltage and voltage frequency-controlled power supply of induction machines used. Such frequency inverters generally have a DC link for converting the mains voltage into a DC voltage. To the DC output is a controlled inverter coupled, in turn, the DC voltage in an AC voltage with a adjustable frequency transferred. The inverter is equipped with power semiconductor switches, in particular Fast-switching power FETs or IGBTs are used. With these transistors used as switching elements is a Sine AC voltage replicated from short pulses of high frequency, by making the output AC voltage small, different broad impulses is composed, so that in this way the normal voltage curve is approximated. Such power semiconductor switches have the advantage that Switching losses are kept small, but burden the steep edges the voltage pulses, especially the insulation materials of the connected Machinery. Furthermore, these short voltage rise times lead to unwanted electromagnetic interference neighboring Signal lines and equipment.

to Avoiding such disturbances and strains it is known to use so-called output sine filters, which have the task High-frequency components of the pulsed output voltage of the inverter filter out, so that only possible the fundamental voltage remains on the connected machine. Such sine filters usually consist of a choke and a capacitor, where the cutoff frequency of the sine filters is between the maximum fundamental frequency and the switching frequency of the inverter is.

These Sinusoidal filters can now work in a three-phase network depending on Application can be realized so that they either only the conductor-to-conductor voltage (differential mode) or else the phase-to-phase or phase-to-phase voltage (common mode). The present invention relates to filters, the differential mode as well as the common mode voltage filter.

Such a filter type is in particular from the EP 0 682 401 B1 known. This document teaches a corresponding filter effect by connecting a differential mode filter and a common mode filter in series, wherein the differential mode filter as a first inductance in this overall filter circuit a largely linear longitudinal inductor and the common mode filter as a second inductor having a current-compensated inductor. Current-compensated choke coils have a common core in which cancel the magnetic fluxes of the fundamental of the machine currents in a symmetrical three-phase system. Only in the case of asymmetrical currents does the choke coil with the participating capacitances of the capacitance network form an LC low-pass filter with which higher-frequency voltage pulses are filtered out. This solution of the cascaded filter thus has the disadvantage that two separate chokes must be used, which require appropriate space and cause costs.

Basically, in the aforementioned embodiment could be dispensed with the common mode throttle. In this case, the remaining throttle would have to be designed such that it acts both in differential mode and in common mode. This is known in particular by a throttle design as three separate single-phase chokes. Such throttle execution is for example in the EP 0 682 395 B1 described. Therein, the arrangement of at least three windings on a core of magnetic material is disclosed, resulting in leakage fluxes, which lead to stray inductances, which in turn are effective as longitudinal inductances, on the other hand flow partial flows through the core and a designated air gap, so that this arrangement also as current-compensated choke acts. However, since in the common mode system high inductance values are required to achieve low filter currents, such individual reactors must be made very large, which makes such a reactor very expensive for both filter purposes.

The present invention is therefore an object of the invention to provide a choke device according to the preamble of claim 1 and a use thereof in a filter circuit and a corresponding filter circuit, which choke device compact and inexpensive and yet in filter systems that both the differential mode and the common Filter mode voltage, can be used effectively is.

The Solution to this problem is inventively at Such a reactor means in that a first Core of magnetic material and at least three arranged on this core Windings are included and that over the at least three Windings each have a second core is arranged, as a Longitudinal inductance acting single choke forms. For the use of this Drosselspuleneinrich device is the object of the invention by the features of the claim 17 and for the filter circuit by the features of the claim 18 solved.

By the filter circuit according to the invention is in particular an output sine filter of one included in a frequency converter Inverter provided by the rising and falling edges the voltage pulses generated by the inverter are reduced, so that a reduction of the burden of isolation in the connected Machines is ensured. At the same time are also disturbances switched off or at least reduced by unbalanced Voltages are caused against the earth potential. To the desired compact and cost-effective To achieve construction, the invention comes Choke coil device used. This is as common Realized component, which functionally one Series connection of a current-compensated choke and one each in each live phase conductor arranged as a longitudinal inductance acting throttle corresponds. This inductor device has a first core of magnetic material on which at least three Windings are arranged. A second core is each about arranged the windings, said second core with the associated Winding each acting as a longitudinal inductance Throttle forms. Such an arrangement allows it, with only one winding per phase line attenuation in both unbalanced (common mode) and symmetric (Differential mode) to adjust admission, with the inductors the two filter systems by an advantageous arrangement of the windings and magnetic paths is reached.

The Core material of the first core advantageously has a high Permeability up. This is a high inductance the current-compensated choke made by this core adjustable, so that the size also kept correspondingly small can be. For a particularly small embodiment it is favorable if the first core is closed magnetic circuit with no or only a small air gap having. In this way, the magnetic scattering is particular reduced compared to a rod.

The Choke coil device is special for their purpose in any case, if the second cores each have an air gap possibly larger than any existing air gap in the first core. Alternatively or additionally the second core also has a lower permeability material as the first core. This ensures that that the common mode flow almost exclusively in the first Kern due to the higher permeable material used there and the smaller or nonexistent air gap flows. The first core thus determines the common mode inductance.

A special embodiment provides that the second core a Horseshoe or U-shaped legs, with his open side, the winding surrounds and to the section of the first Kerns, which carries the winding, is coupled, whereby the Coupling in particular via an air gap on one or takes place at both coupling points. Generated in this second core each associated winding is independent of its own flow from the other windings, leaving the core material of the second Kerns and the possibly existing air gaps the river for determine the differential mode system and thus the height Define the inductance for this system. Close the flows for the differential mode system in the first core. Is in the design of a specific inductor device required that an air gap be provided in the first core, so it is convenient to this in a subsection of this Kerns to arrange in which no second core is coupled.

Around a particularly compact design of the inductor device can reach the first core and the second cores be arranged at an angle to each other, so that a three-dimensional Arrangement is given. In this way is the space requirement in an arrangement of the inductor device on a circuit board kept low. In particular, forms in an arrangement of the first core and the second cores at right angles to each other at least approximately a cube shape.

In a further embodiment, the first core is configured in an elongated, in particular rectangular shape, so that at least one rectilinear section is formed thereon, on which the three windings are arranged next to one another. This embodiment is advantageous if only an elongated throttle fits into the installation site. This elongated throttle arrangement can again be represented in a three-dimensional manner, as explained above. In addition, there is still an optimization in terms of space requirements and material use in such a way that the second cores on the we at least three adjacent windings are summarized into a single component, which forms an E-shaped figure with at least four prongs.

Regarding the optimization of the size is yet another Embodiment conceivable. This is that the first core and the second core lie in one plane, however the second core disposed within the area bordered by the first core is. This in turn can horseshoe or U-shaped second Cores are the case, all of them inside the first core meet and also touch. A very space-optimized Solution, however, provides a structure with a first core, which is formed as a toroidal core, and with a second core, the is star-shaped and comprises at least three arms. each Armende delimits one winding from one adjacent one. Since in this way two adjacent windings having an arm of the second core in common, becomes very much of the second core material little mass needed.

After all will be mentioned a fourth embodiment become. In this case, the second core material consists of a magnetic conductive potting compound. In this case, from the first core and the windings arranged thereon, first a common Mode throttle produced and this subsequently in the magnetically conductive material are poured. A Such representation of the inductor device according to the invention is particularly suitable because of the core material of the second Kerns no particularly high permeability is required.

The Core material of the second core may also be referred to as magnetically conductive Sintered material, for. As iron powder, be prepared, wherein the inductor device is generated in particular by the fact that the first core with the at least placed three windings in a sintered mold and surrounded with sintered material and then performed a sintering process becomes.

The The invention is described below with reference to the drawings of several embodiments explained in more detail. Showing:

1 a frequency converter for speed control of induction machines with an output filter;

2 to 5 various embodiments of inductor devices used for the output filter; and

6 the arrangement of the inductor device in a three-phase network in front of an actively pulsed mains converter.

1 shows a designated for speed control of induction motors frequency converter, of which, however, only a DC intermediate circuit (symbolized by a capacitor 1 ) and an inverter connected to it 3 are shown. The DC link is powered by a connected to the power grid with a constant voltage and constant frequency, in this figure is not asked power rectifier. The inverter 3 sets the DC voltage provided by the DC link with the help of power semiconductor switches 5 into a three-phase three-phase network and puts this at its output terminals 7 with variable frequency and voltage for the connected, not shown here three-phase machine, in particular a three-phase motor available.

As a circuit breaker 5 For example, FETs or IGBTs are used. These have very steep rising edges of the pulses generated. This will cause the losses in the inverter 3 kept low, allowing a correspondingly high efficiency of the inverter 3 is guaranteed. On the other hand, these steep rising edges cause high failure to polarize within the winding insulation in the connected induction machines to fail due to fatigue and thus to a reduced life of these machines.

To counteract these failures is at the output of the inverter 3 an output sine filter 9 connected. In the present example, this comprises a choke coil device 11 and a capacitor network 13 , The capacitor network 13 is used in the three-phase network in such a way that the individual capacitors ( 15 . 17 . 19 . 21 ) between the phase conductors 23 as well as between the ladders 23 and earth potential 25 are arranged. This is done by having three capacitors 15 . 17 . 19 in a star connection to the three phase conductors 23 are connected and the neutral point via a fourth capacitor 21 with the earth 25 connected is.

As a choke coil device 11 comes for the circuit according to 1 one of the embodiments according to 2 to 5 for use.

2 shows the construction of a first reactor means 11 , This includes a common first core 27 which approximates a square frame shape. On three sides of this first core 27 is each a winding 29 arranged, with each of these windings 29 in each case a phase line 23 is used. Together with the common first core 27 thus results in a current-compensated choke in the three-phase network. About every winding 29 is a second core 31 arranged, together with the associated winding 29 has a single-choke effect and a lower-permeability material than the first core 27 consists. The arrangement is realized such that each second core configured in a rectangular U-shape 31 with the ends of its free legs via an air gap 33 to the section of the first core 27 is attached, on which the associated winding 29 located.

The windings 29 are switched in the same direction and wound, so that a differential mode current in the first core 27 does not generate a river. In the second nuclei 31 generates each of the windings 29 their own flow independent of the other windings 29 so that the material of the second nuclei 31 and the air gaps 33 determine the flow for the differential mode system, which also defines the level of inductance for this system. In the respective subsection of the first core 27 this river closes. Because of the comparatively high permeability of the material of the first core 27 this does not affect the differential mode inductance. However, the first core is 27 able to guide the differential mode rivers.

For common mode currents, the fluxes of the three windings stand out 29 in the first core 27 not up. Because of the high permeability of the material of the first core 27 the common mode flow flows almost exclusively in the first core 27 so that the material of the first core 27 the common mode inductance decisively determined.

In the example below 2 is in the first core 27 no air gap provided. However, in the dimensioning of the inductor device 11 such an air gap is considered necessary, it is preferable to insert it at a location where there is no second core 31 is arranged in parallel. For this purpose, in the present example, the side of the square core is suitable 27 on, no winding 29 wearing.

The in 2 illustrated planar structure may alternatively be shown as a three-dimensional structure. This can be done by folding up the second cores 31 be ensured perpendicular to the plane, so that there is a cube-shaped structure. But in principle, each angular position of the second cores is in a space-optimized manner 31 to the first core 27 conceivable, if this is geometrically possible. It is also conceivable that the second nuclei 31 take a triangular shape instead of a U-shape and these are arranged so that a pyramid shape with the first core 27 as a base.

3 shows a second variant of the choke coil device 11 , This is an alternative solution to the aforementioned construction with an elongate shape. Here is the first core 27 designed as an elongated rectangle. One of the two longer thighs 35 serves for the juxtaposition of the three windings 29 , The other three sides of the rectangle do not carry a winding 29 , This variant has the advantage that the adjacent legs of the second cores formed in turn in a rectangular U-shape 31 can be configured as a common leg, so that for the second core material 31 an E-shaped figure with four prongs results.

A further advantageous, particularly compact embodiment is in 4 shown. In this are the second cores 31 inside the first core 27 arranged. To minimize the mass of the second core material, these are second cores 31 united into a single component, namely a star-shaped arrangement with three arms 37 , The first core is as a ring core 39 educated. In this way, a structure similar to a cartwheel with three spokes results. Between every two of these arms 37 is on the toroid 39 one winding each 29 wound. Winding direction and circuit of the windings 29 are here again - as in all present embodiments - in the same direction. Should be in accordance with this variant 4 To arrange an air gap, so is a place where one of the arms 37 of the inner star at the toroidal core 39 abuts. Also in this variant is between the two core materials 27 . 31 an air gap 33 intended.

Furthermore, with reference to 5 a fourth advantageous variant of the choke coil device according to the invention 11 explained. In this is the material of the second core 31 a magnetically conductive potting compound 41 , The structure of this device is made by introducing a common mode throttle from the first core 27 and the windings 29 , This will subsequently be in the magnetically conductive material 41 cast. An "air" gap can be realized by placing a skin of a second potting compound of magnetically nonconductive material before casting the second core material around the initially produced common mode throttle.

Finally shows 6 a network-side arrangement of the filter circuit in a three-phase network N, which is connected upstream of an actively pulsed mains converter. In this illustration, the filter circuit is in front of one of the mains current ter included rectifier circuit 43 set to protect against interference voltages in the three-phase network N.

Through all the aforementioned solution variants can save a lot of space and material a choke coil device 11 be realized, which has a very high inductance in the common mode system and a low inductance in the differential mode system. As a result, instead of the two previously used Dros seln only one can be used. Advantages arise in terms of small footprint and low material costs.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• EP 0682401 B1 [0005]
• - EP 0682395 B1 [0006]

Claims (19)

A choke coil device for a filter circuit, in particular for an output sine filter of an inverter included in a frequency converter, which is designed so that it functionally corresponds to a series connection of a current-compensated choke and arranged in each live phase line, acting as a longitudinal inductance choke, characterized in that a first core ( 27 ) of magnetic material and at least three on this core ( 27 ) arranged windings ( 29 ) and that over the at least three windings ( 29 ) in each case a second core ( 31 ) is arranged, which forms a longitudinal inductance acting as a single throttle. Choke coil device according to claim 1, characterized in that the first core ( 27 ) has a high permeability. Choke coil device according to claim 1 or 2, characterized in that the first core ( 27 ) has no or only a small air gap. Choke coil device according to claim 2 or 3, characterized in that the second core ( 31 ) a larger air gap ( 33 ) as the first core ( 27 ) and / or a material having a lower permeability than the first core (FIG. 27 ). Choke coil device according to one of claims 1 to 4, characterized in that the second core ( 27 ) has a horseshoe or U-shaped leg, with its open side, the winding ( 29 ) and to the partial section of the first core ( 27 ), which the winding ( 29 ) is coupled. A choke device according to claim 5, characterized in that between the horseshoe or U-shaped leg and the portion of the first core ( 27 ) at least at one Ankoppelstelle an air gap ( 33 ) is provided. Choke coil device according to claim 5 or 6, characterized in that the partial section of the first core ( 27 ) is configured such that the magnetic flux of the individual throttle is feasible. Choke coil device according to one of claims 1 to 7, characterized in that in the first core ( 27 ) an air gap is provided in a subsection in which no second core ( 31 ) is coupled. Choke coil device according to one of claims 1 to 8, characterized in that the two planes in which the first ( 27 ) and the second core ( 31 ), an angle, in particular a right angle, include. Choke coil device according to one of claims 1 to 9, characterized in that the at least three windings ( 29 ) side by side on a rectilinear section of the first core ( 27 ) are arranged. Choke coil device according to claim 10, characterized in that the second cores ( 31 ) over these at least three windings ( 29 ) are combined into a single component, which forms an E-shaped figure with at least four prongs. Choke coil device according to one of claims 1 to 8, characterized in that the first ( 27 ) and the second core ( 31 ) lie in one plane and the second core ( 31 ) within the first core ( 27 ) bordered surface is arranged. Choke coil device according to claim 12, characterized in that the first core ( 27 ) as ring core ( 39 ) and the second core ( 31 ) star-shaped with at least three arms ( 37 ) are configured. Choke coil device according to one of claims 1 to 4, characterized in that the core material of the second core ( 31 ) as a magnetically conductive potting compound ( 41 ) is executed. Choke coil device according to one of claims 1 to 13, characterized in that the core material of the second core ( 31 ) is designed as a magnetically conductive sintered material, in particular iron powder. A choke coil device according to claim 15, which is manufactured in such a way that the first core ( 27 ) with the at least three windings ( 29 ) is placed in a sintering mold and surrounded with sintered material and then a sintering process is performed. Use of the choke coil device according to one of claims 1 to 16 in a filter circuit for limiting the rate of change of currents and voltages between live lines ( 23 ) and against the earth potential ( 25 ), in particular for a frequency converter or as a line filter for electromagnetic compatibility or as a filter arrangement in front of an actively pulsed mains converter. Filter circuit, in particular three-pha sen filter circuit, for limiting the rate of change of currents and voltages between live lines and against the ground potential, in particular for a frequency converter or as a line filter for electromagnetic compatibility or as a filter arrangement in front of an actively pulsed mains converter, with a capacity ( 15 . 17 . 19 . 21 ) and inductors having LC low pass, where at all inductances to the inductor means ( 11 ) are summarized according to one of claims 1 to 16. Filter circuit according to Claim 18, characterized in that the choke coil device ( 11 ) a capacitor network ( 13 ) upstream or downstream, the capacitors ( 15 . 17 . 19 . 21 ) between the ladders ( 23 ) and between the ladders ( 23 ) and earth potential ( 25 ) or intermediate circuit or network star point are arranged so that differential mode and common mode voltages can be filtered.