Frequency converter and arrangement unit comprising frequency converter and polyphase motor or transformer

Abstract

The utility model relates to a frequency converter and a setting unit formed by the frequency converter and a multi-phase motor or a transformer, which are used for supplying power to the multi-phase motor (3) or the transformer, and comprise a power supply converter (4) with a first semiconductor switch and used for converting alternating current voltage into direct current voltage; a machine converter (6) with a controllable second semiconductor switch for converting the DC voltage into a supply voltage; and a voltage intermediate circuit (5) carrying a DC voltage, the voltage intermediate circuit having an upper and a lower intermediate circuit branch connected to each other at a common center point (16). The machine converter consists of only two half-bridges containing second semiconductor switches for providing the first phase at the first output interface and the second phase at the second output interface. A center point (16) is provided at the third output interface. The power converter (4) is formed by a plurality of half-bridges comprising first semiconductor switches. The semiconductor switches are integrated in a single power electronic component.

Description

Technical Field

[0001] This utility model relates to a frequency converter for providing a variable frequency and amplitude supply voltage to a multiphase motor or transformer. It includes: a power converter with a first semiconductor switch for converting single-phase or multiphase AC voltage from a power grid into DC voltage; a machine converter with a controllable second semiconductor switch for converting the DC voltage into a supply voltage; and a voltage intermediate circuit carrying the DC voltage, arranged between the power converter and the machine converter. This voltage intermediate circuit consists of an upper intermediate circuit branch and a lower intermediate circuit branch interconnected at a common center point. The upper intermediate circuit branch connects its center point to a first pole of the voltage intermediate circuit via at least one upper capacitor, and the lower intermediate circuit branch connects its center point to a second pole of the voltage intermediate circuit via at least one lower capacitor. Furthermore, this utility model also relates to an installation unit consisting of such a frequency converter and a multiphase motor or transformer, wherein the multiphase motor or transformer can be powered by the frequency converter. Background Technology

[0002] Motors typically need to operate at varying speeds. However, when multiphase motors operate directly on a so-called "rigid" power grid, the speed is essentially fixedly coupled to the grid frequency. Frequency converters are used for decoupling; however, these converters incur additional costs and energy losses. According to existing technology, this is typically done as follows: Figure 1 As shown in the figure, a frequency converter is used, in which Figure 1 The entire drivetrain configuration is shown. The inverter 2 first converts the AC power from the power grid 1 into DC power using a power converter 4. The power converter 4 can be either a rectifier, such as the diode rectifier in a B2 bridge circuit, or an active power factor correction (PFC) circuit, where the latter includes a rectifier connected in series with the downstream coil and a controlled semiconductor switch that temporarily short-circuits this series circuit. Alternatively, other topologies for active power factor correction exist, which can be obtained from relevant literature.

[0003] A capacitor C connected to power converter 4 and used as an energy storage device dc In the intermediate voltage circuit 5, the generated DC voltage is stabilized, thereby compensating for fluctuations in power supplied from the power grid 1 to the intermediate voltage circuit 5 by the power converter 4, or for fluctuations in power obtained by the load from the intermediate voltage circuit 5. The load here is a machine converter 6 that converts the DC voltage into a three-phase AC voltage with variable amplitude and frequency. The phase position of the AC voltage can also be adjusted. In other words, the DC power from the intermediate voltage circuit 5 is converted into three-phase AC power, which is used to operate the connected multiphase electric motor 3.

[0004] Here, according to Figure 1 The machine converter 6 typically consists of three identical half-bridges H1, H2, and H3, all connected in parallel with the voltage intermediate circuit and each providing one phase of the supply voltage for the multiphase motor 3. Each half-bridge comprises an upper branch and a lower branch, each containing a controllable power electronic semiconductor switch. Therefore, each half-bridge consists of two such switches, with the supplied phase positioned between the semiconductor switches. The first half-bridge H1 is composed of semiconductor switches T1 and T2, the second half-bridge H2 is composed of semiconductor switches T3 and T4, and the third half-bridge H3 is composed of semiconductor switches T5 and T6. Furthermore, each semiconductor switch T1...T6 in the machine converter 6 is connected in anti-parallel to a freewheeling diode D1...D6 in a known manner. The corresponding phase is connected to the first terminal 17 of the voltage intermediate circuit 5 via the respective upper branch, i.e., via semiconductor switches T1, T3, and T5, which serves as the positive terminal. Accordingly, the second terminal 18 of the corresponding phase-voltage intermediate circuit 5 is connected via the corresponding lower branches, namely via semiconductor switches T2, T4, and T6, which constitutes the negative terminal. The two semiconductor switches of the same half-bridge are thus reversed, so that one is in the on state while the other is in the off state.

[0005] By properly manipulating semiconductor switches, such as pulse width modulation or space vector modulation, AC voltages can be generated on each phase in this way, thus forming a three-phase AC voltage system, i.e., a three-phase current system.

[0006] The converter topology described is called a "three-way two-level" converter or a "three-way two-point" converter, where the term "three-way" refers to the three phases formed, and the term "level" refers to the voltage level of the intermediate voltage loop.

[0007] Controllable power electronic semiconductor switches are typically MOSFETs (Metal Oxid Semiconductor Field-Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors). They are provided as a single, centralized component for constructing machine converters, where the semiconductor switches are integrated into a single housing that is, in the form of a power module. These components or power modules are manufactured, for example, by Infineon Technologies AG (Munich, 81726, Germany), such as IGBTs with product names FS3L25R12W2H3_B11, FS25R12W1T4, FS25R12W1T7P_B11, and FS150R17N3E4_B11, or MOSFETs with product name FS55MR12W1M1H_B11. "Simmons Electronics GmbH & Co. KG" (Sigmundstr. 200, Nuremberg 90431, Germany) also offers power modules under the product names SK35GD12T4ET, SK25TMLID12F4TE2 and SKiiP 11AC126V10, while "Werke Electronics GmbH" (Biberger Straße 93, 82008 Winterhaching, Germany) offers power modules under the product names 10-F1126PA025M7-L826F09, V23990-K238-F40, V23990-P708-F40-FM and V23990-P829-F08x, which have six or more integrated IGBTs, some of which are already connected.

[0008] The controllable semiconductor switches in the machine converter and the diodes in the power converter 4 are expensive and generate losses in the form of heat (conversion losses and conduction losses) during operation, which must be dissipated and reduce efficiency. Utility Model Content

[0009] The purpose of this invention is to reduce and optimize the conversion costs and expenses of single-phase power supply frequency converters.

[0010] This objective is achieved by a frequency converter according to the present invention. The frequency converter is used to provide a variable frequency and amplitude supply voltage for a multiphase motor or transformer. The frequency converter includes: a power converter with a first semiconductor switch for converting a single-phase or multi-phase AC voltage from a power grid into a DC voltage; a machine converter with a controllable second semiconductor switch for converting the DC voltage into a supply voltage; and a voltage intermediate circuit carrying the DC voltage arranged between the power converter and the machine converter. This voltage intermediate circuit consists of an upper intermediate circuit branch and a lower intermediate circuit branch interconnected at a common center point. The upper intermediate circuit branch connects its center point to a first pole of the voltage intermediate circuit via at least one upper capacitor, and the lower intermediate circuit branch connects its center point to a second pole of the voltage intermediate circuit via at least one lower capacitor. According to this utility model, a frequency converter of the type described at the beginning is developed in the following manner: the machine converter consists of only two identical half-bridges containing second semiconductor switches, for providing a first phase of supply voltage at a first output interface and a second phase of supply voltage at a second output interface, wherein the machine converter is provided with a center point for providing a voltage intermediate loop at a third output interface, and the power converter consists of several half-bridges, particularly a number of half-bridges corresponding to the number of phases in the power grid, wherein the half-bridges are constructed identically to the half-bridges of the machine converter and contain first semiconductor switches, wherein the first and second semiconductor switches are physically integrated into a single centralized power electronic component.

[0011] Therefore, the characteristic of the frequency converter of this utility model is that the voltage intermediate circuit is segmented, and the machine converter is composed of only two half-bridges instead of three, thus saving at least two controllable semiconductor switches in the machine converter. Therefore, the machine converter can be composed of only four, instead of six, semiconductor switches. This reduces heat loss. However, these semiconductor switches must have twice the voltage withstand capability compared to a machine converter with six semiconductor switches, under the same output voltage. Therefore, a three-phase AC motor or transformer is only powered on two phases; however, by properly manipulating the semiconductor switches at the three output interfaces, a three-phase current system can be re-established. The topology of the machine converter can be called a four-switch-three-way-two-level topology.

[0012] On the other hand, the present invention employs a single / unique power electronic component that integrates not only the second semiconductor switch required for the machine converter, but also the first semiconductor switch required for the power converter. This component is readily available economically and can accommodate semiconductor switches within a limited space.

[0013] From another perspective, although the machine converter has only two half-bridges, at least six semiconductor switches for at least three half-bridges can be integrated into the power electronics. At least four of these six semiconductor switches in the power electronics are used for the two half-bridges of the machine converter, while the remaining semiconductor switches are used for one or more half-bridges in the power converter.

[0014] Since all half-bridges are identical, the power converter also has controllable semiconductor switches, which not only rectify the AC voltage of the power grid but also enable power factor control (PFC).

[0015] The use of power electronics components reduces the shared structural space for machine converters and power converters. It also significantly reduces the conversion costs and expenses of frequency converters with unidirectional power converters.

[0016] Furthermore, under appropriate control, such a frequency converter can also feed the electrical energy of multiphase motors or transformers back to the power grid, which is advantageous for certain applications of variable speed drive devices in the case of multiphase motors.

[0017] In addition, the controllable semiconductor switch of the power converter can also exchange reactive power with the power grid. This reactive power can be determined in advance by a higher-level unit that controls the first semiconductor switch, which is essentially independent of other operations of the frequency converter and therefore free to do so. This can help stabilize the power grid and / or compensate for the reactive power of other consumers.

[0018] Preferably, the power electronics integrate exactly three, four, or five identical, independent half-bridges, wherein a first semiconductor switch within the component is connected as a half-bridge for a power converter and a second semiconductor switch is connected as a half-bridge for a machine converter. This further reduces conversion / switching costs. If the power electronics has three independent half-bridges, two can be used for the machine converter, and the remaining third half-bridge can be used to form a single-phase power converter. Alternatively, if the power electronics has five independent half-bridges, two can be used for the machine converter, and the remaining three half-bridges can be used to form a three-phase power converter. As a further alternative, four independent half-bridges can be integrated into the power electronics, two for the machine converter and the remaining two for a three-phase power converter, which operates using only two phases of the power grid. Therefore, in this variant embodiment, a four-switch-three-way-two-level topology is used for both the machine converter and the power converter.

[0019] As a power electronic component, one of the power modules from Infineon, Semikron, or Wolverine Electronics mentioned in the preface of the instruction manual can be used.

[0020] It should be noted that, in addition to the half-bridge, the power electronic components can also integrate one or more other components, such as an additional controllable semiconductor switch. This semiconductor switch can be used, for example, as a so-called "braking chopper" to connect a capacitor C in the intermediate circuit. dc A resistor is connected in parallel, and through this resistor, energy from the intermediate voltage circuit is converted into heat. For example, Vincotech can provide a power module with three half-bridges and an additional controllable semiconductor switch that can be used as a power electronics component, named "Sevenpack", such as product number 10-FZ127PA008SC-L156E08.

[0021] As described above, the power converter in the first variant embodiment can be composed of a single / unique half-bridge and is therefore single-phase for operation on a single-phase power supply network. This half-bridge of the power converter can be composed of an upper and a lower power converter branch and has a first input node that interconnects the upper and lower power converter branches and is configured for connection to a first conductor of the single-phase power supply network. The upper power converter branch connects the input node to a first pole of the DC voltage via at least one upper controllable semiconductor switch of the first semiconductor switch, and the lower power converter branch connects the input node to a second pole of the DC voltage via at least one lower controllable semiconductor switch of the first semiconductor switch. This arrangement allows the energy of both the positive and negative half-waves of the AC voltage to be delivered to the intermediate circuit using a single half-bridge. Therefore, to deliver the positive half-wave energy, the upper semiconductor switch is switched to the conducting state, and to deliver the negative half-wave energy, the lower semiconductor switch is switched to the conducting state.

[0022] In a second variant embodiment, the power converter may consist of three half-bridges, and is therefore three-phase, for operation on a three-phase power supply network. In a third variant embodiment, the power converter may consist of two half-bridges and is therefore two-phase, yet can operate on a three-phase power supply network. Each of the half-bridges in the second and third variant embodiments may consist of an upper and a lower power converter branch and have an input node that interconnects the upper and lower power converter branches of the respective half-bridge and is configured for connection to one phase of the three-phase power supply network. The upper power converter branch of each half-bridge connects the corresponding input node to the first pole of the DC voltage via at least one upper controllable semiconductor switch of the first semiconductor switch, and the lower power converter branch of each half-bridge connects the corresponding input node to the second pole of the DC voltage via at least one lower controllable semiconductor switch of the first semiconductor switch. This arrangement enables the operation of the frequency converter of this invention on a three-phase power supply network.

[0023] In a third variant embodiment, the power converter comprises a first half-bridge with a first input node and a second half-bridge with a second input node, wherein the first input node is configured to connect to the first phase of the three-phase power supply network, and the second input node is configured to connect to the second phase of the three-phase power supply network. The frequency converter is then configured to provide a third input node, which is connected to the center point of the voltage intermediate loop and configured to connect to the third phase of the three-phase power supply network. In this way, the power converter in the third variant embodiment is powered by two phases, yet operates on a three-phase power supply network.

[0024] In the case where the frequency converter of this utility model is operating on a single-phase power supply network, the center point of the voltage intermediate circuit can constitute a second input node and be configured to connect with a second conductor of the single-phase power supply network.

[0025] Preferably, the second conductor is the neutral wire of the power supply network, so that the center point can be regarded as a zero point or ground wire. Based on this center point, the first pole can have a positive potential, thus forming the positive pole of the DC voltage, while the second pole can have a negative potential, thus forming the negative pole of the DC voltage. Therefore, the first conductor is a phase of the single-phase power supply network that supplies power to a half-bridge. However, it is also possible, and technically the same, to use the neutral wire of the power supply network as the first conductor and the phase of the power supply network as the second conductor, so that the phase is connected to the center point of the voltage intermediate loop as the second input node, and the neutral wire is connected to the first input node.

[0026] Each of the half-bridges of the machine converter can be composed of an upper and a lower machine converter branch, wherein the upper and lower machine converter branches of the first half-bridge of the two half-bridges are interconnected at a common first output node and connected to a first output interface, and the upper and lower machine converter branches of the second half-bridge of the two half-bridges are interconnected at a common second output node and connected to a second output interface, wherein the upper machine converter branch of the first half-bridge and the upper machine converter branch of the second half-bridge connect their respective output nodes to the first pole of the DC voltage through at least one upper controllable semiconductor switch of the second semiconductor switch, and the lower machine converter branch of the first half-bridge and the lower machine converter branch of the second half-bridge connect their respective output nodes to the second pole of the DC voltage through at least one lower controllable semiconductor switch of the second semiconductor switch.

[0027] According to one development, each branch of the half-bridge may include two series-connected controllable semiconductor switches, with a connection point between each switch. From each connection point, a bridging wire connects to the center point via a diode oriented towards the positive potential. This arrangement allows the first and second output ports of the machine converter to be connected to the center point, i.e., the zero point is switched to the first or second phase of the supply voltage for a multiphase motor or transformer. This allows three different potentials to be connected to the respective output ports of the machine converter: the potential of the first pole (positive), the potential of the second pole (negative), and the potential of the center point (zero or ground).

[0028] In addition, this utility model also relates to a setting unit consisting of a frequency converter of the above type and a multiphase motor or transformer, wherein the multiphase motor or transformer is powered by the frequency converter during operation and is connected to a first output interface via a first feeder line, a second output interface via a second feeder line, and a third output interface via a third feeder line.

[0029] The setup unit may suitably include a machine filter arranged between the frequency converter and the multiphase motor or transformer. This machine filter consists of two inductors and two or three capacitors. One of the inductors is arranged in a first feed line, and the other inductor is arranged in a second feed line. One of the capacitors, located between the multiphase motor or transformer and the corresponding inductor, connects the first feed line, and the second capacitor connects the second feed line to a potential in the voltage intermediate circuit—that is, the same potential. Since the multiphase motor or transformer is only powered by two phases, this saves one inductive filter element—the filter element in the third feed line—compared to existing technologies.

[0030] The potential of the intermediate voltage loop can be the center point (neutral point), the first pole (positive), or the second pole (negative). If the first or second pole is used as the potential, the third capacitor in the machine filter can connect the third feed line to this potential. However, it is advantageous to use the center point as the potential. Since the third feed line is already connected to the center point, the third capacitor can be omitted in this case. Therefore, it is suitable to design the machine filter to consist of two inductors and only two capacitors, which connect one of the first and second feed lines to the third feed line, respectively.

[0031] In the case of using a frequency converter with exactly two half-bridge power converters according to the third variant embodiment, as a supplementary or alternative to the machine filter, the unit may have a power filter located between the power grid and the frequency converter. This power filter can be configured similarly to the machine filter, consisting of two inductors and two or three capacitors. One of the inductors connects the first input node to the first phase of the power grid, the other inductor connects the second input node to the second phase of the power grid, and one of the capacitors connects the first input node and the second capacitor connects the second input node to a potential in the voltage intermediate loop, i.e., the same potential. Since the power converter supplies power only two phases, this case also saves an inductive filter element compared to the prior art—the filter element connecting the third phase of the power grid to the power inverter.

[0032] In a power filter, the potential in the intermediate voltage loop can be the center point (neutral point), the first pole (positive), or the second pole (negative). If the first or second pole is used as the potential, the third capacitor in the power filter can connect the third input node to this potential. However, it is also advantageous to use the center point as the potential, since the third input node is already connected to the center point, thus omitting the third capacitor. Therefore, it is suitable to design the power filter to consist of two inductors and only two capacitors, wherein the capacitors connect the first and second input nodes to the third input node, respectively.

[0033] It should be noted that each of the capacitors can be constructed from one or more capacitors. Correspondingly, each of the inductors can be constructed from one or more coils.

[0034] The preferred application of the setting unit is that the multiphase motor is a pump motor for a centrifugal pump, that is, a motor that drives a centrifugal pump. Attached Figure Description

[0035] The further features, advantages, and characteristics of this utility model are described in detail below with reference to embodiments and accompanying drawings. In the drawings, the same numerals or reference numerals denote the same or at least equivalent equivalent components, parts, surfaces, or orientations.

[0036] It should be noted that, within the scope of this specification, the terms "having," "including," or "comprising" do not exclude the presence of other features. Furthermore, the use of the indefinite article to describe an object does not exclude its plural form.

[0037] As long as they are not technically mutually exclusive, features of one variant of this invention may also appear in another variant. Furthermore, the method features may appear in one of the devices described herein, and the device features may also appear in the method described herein.

[0038] Figure 1 A schematic equivalent circuit diagram of a frequency converter according to the prior art is shown on a single-phase power supply network for driving a multi-phase electric motor.

[0039] Figure 2 The equivalent circuit diagram of the frequency converter of the present invention is shown. The frequency converter includes: a machine converter with a four-switch-three-way-two-level topology, which has an active power converter on a single-phase power supply network; and a first power electronic component with semiconductor switches for the power converter and the machine converter.

[0040] Figure 2a The equivalent circuit diagram of the frequency converter of the present invention is shown. The frequency converter includes: a machine converter with a four-switch-three-way-two-level topology, which has an active power converter on a three-phase power supply network; and a second power electronic component with semiconductor switches for the power converter and the machine converter.

[0041] Figure 2b The equivalent circuit diagram of the frequency converter of the present invention is shown. The frequency converter includes: a machine converter with a four-switch-three-way-two-level topology, which has an active power converter with a four-switch-three-way-two-level topology on a three-phase power supply network; and a third power electronic component with semiconductor switches of the power converter and the machine converter.

[0042] Figure 3a An equivalent circuit diagram of another power electronic component is shown, which incorporates semiconductor switches for a power converter and a machine converter.

[0043] Figure 3b An equivalent circuit diagram of another power electronic component is shown, which incorporates semiconductor switches for a power converter and a machine converter.

[0044] Figure 4The equivalent circuit diagram of the frequency converter of this utility model is shown. The frequency converter includes: an eight-switch-three-way-three-level topology machine converter with an active power converter on a single-phase power supply network.

[0045] Figure 5 The equivalent circuit diagram of a machine filter (EMV filter) arranged after the machine converter is shown. Detailed Implementation

[0046] Figure 1 The diagram shows a conventional frequency converter 2 installed on a single-phase power supply network 1. This converter includes a pre-amplitude power filter 28 (EMV filter) to reduce harmonics generated by the converter 2. The converter 2 provides three-phase voltage to a multi-phase motor 3, such as a permanent magnet synchronous motor. This permanent magnet synchronous motor drives, for example, a centrifugal pump (not shown here), and thus constitutes the pump motor for the centrifugal pump. A machine filter 29 (EMV filter) is connected between the frequency converter 2 and the multi-phase motor 3. (The last sentence appears to be incomplete and possibly refers to a separate section.) Figure 1 The topology of inverter 2 with a "three-way two-level" structure has been described, so please refer to the detailed description at the beginning of the instruction manual.

[0047] Figure 2 An example of the frequency converter 2 of this utility model is shown. First, it is connected with... Figure 1 The difference between the conventional frequency converter 2 and the conventional one is that the machine converter 6 consists only of four controllable semiconductor switches T3, T4, T5, and T6 from two identical half-bridges 10 and 12. The semiconductor switches T3, T4, T5, and T6 are composed of IGBTs, and each has an anti-parallel freewheeling diode D3, D4, D5, and D6 connected between its generator and collector. The semiconductor switches T3, T4, T5, and T6 provide the first phase of the power supply voltage to the multiphase motor 3 at the first output interface 14a of the frequency converter 2, and the second phase of the same voltage at the second output interface 14b. The third output interface 14c of the frequency converter 2 is connected to the center point 16 of the voltage intermediate circuit 5, which is also connected to the neutral line N of the power grid 1. The multiphase motor 3 is connected to the first output interface 14a via a first feeder line 32a, to the second output interface 14b via a second feeder line 32b, and to the third output interface 14c via a third feeder line 32c. Therefore, the multiphase motor 3 is powered only through the first and second feeder lines 32a and 32b, i.e., two-phase power supply, and can still control the semiconductor switches T3, T4, T5 and T6 in the following way, i.e., there is a three-phase current system, i.e. three-phase power supply voltage, on the three output interfaces 14a, 14b and 14c.

[0048] Therefore, each half-bridge 10, 12 of the machine converter 6 consists of an upper machine converter branch 10a, 12a and a lower machine converter branch 10b, 12b. The upper machine converter branch 10a and the lower machine converter branch 10b of the first half-bridge 10 are interconnected at a common first output node 11 and connected to the first output interface 14a. The upper machine converter branch 12a and the lower machine converter branch 12b of the second half-bridge 12 are interconnected at a common second output node 13 and connected to the second output interface 14b. The corresponding upper machine converter branches 10a and 12a of the first and second half-bridges 10 and 12 connect the corresponding output nodes 11 and 13 to the positive terminal 17 of the DC voltage of the intermediate voltage circuit 5 via at least one upper controllable semiconductor switch T3 and T5, while the corresponding lower machine converter branches 10b and 12b of the first and second half-bridges 10 and 12 connect the corresponding output nodes 11 and 13 to the negative terminal 18 of the DC voltage of the intermediate voltage circuit 5 via at least one lower controllable semiconductor switch T4 and T6. Therefore, by correspondingly manipulating the semiconductor switches T3, T4, T5, and T6, the positive terminal 17 or the negative terminal 18, i.e., two different voltage levels, can be selectively connected to the corresponding output nodes 11 and 13 or the first or second output interfaces 14a and 14b in such a way that the corresponding semiconductor switches T3, T4, T5, and T6 are in a conductive state. Here, the semiconductor switches T3, T4, T5, and T6 of the same half-bridge 10 and 12 are reverse-operated in a well-known manner, so that only one of the corresponding switches is in a conductive state, while the other switches are in a blocking state. Therefore, the inverter 2 has a topology structure (which can be called a four-switch-three-way-two-level topology).

[0049] and Figure 1 A further difference in the conventional frequency converter 2 is that the voltage intermediate circuit 5 is divided into two parts, namely, having a midpoint tap at the center point 16. It consists of an upper intermediate circuit branch 9a and a lower intermediate circuit branch 9b connected to each other at the common center point 16. Simultaneously, the center point 16 is connected to the neutral line N of the power supply network 1, thus placing this center point at a defined potential, i.e., zero, which constitutes the ground line of the DC voltage of the voltage intermediate circuit. The upper intermediate circuit branch 9a is connected via at least one upper capacitor C. dc The center point 16 is connected to the positive terminal 17 of the intermediate voltage circuit 5, while the lower intermediate circuit branch 9b is connected through at least one lower capacitor C. dcThe center point 16 is connected to the negative terminal 18 of the voltage intermediate circuit 5. In practice, multiple capacitors can be arranged in the upper and / or lower intermediate circuit branches 9a, 9b. Therefore, the negative terminal 18 of the voltage intermediate circuit 5 is not grounded as usual, but has a negative potential relative to the center point 16, which quantitatively corresponds to the potential of the positive terminal due to the symmetry of the voltage intermediate circuit. Therefore, in the upper and lower intermediate circuit capacitors C... dc Each of the above acts as half of the intermediate circuit voltage.

[0050] and Figure 1 The third difference between the conventional frequency converter 2 and the machine converter 6 is that the structure employs a power electronics component 15, which integrates more semiconductor switches or half-bridges than the four semiconductor switches T3, T4, T5, T6 or two half-bridges 10, 12 required by the machine converter 6. In this case, it uses three identical, independent half-bridges 7, 10, 12 or six semiconductor switches T1, T2, T3, T4, T5, T6. From another perspective, it can be seen as... Figure 1 The conventional frequency converter 2 uses the same power electronics 15 as the machine converter 6, but only the two half-bridges 10 and 12 in this component 15 are used.

[0051] This forms the relative position of the frequency converter 2 of this utility model. Figure 1 The advantages and four differences of the frequency converter in this article are that the remaining third half-bridge 7 of the power electronics component 15 is used to implement the power converter 4. Figure 2 This is illustrated by the area drawn with shaded lines within a frame representing component 15, which graphically surrounds the machine converter 6 and the power converter 4. Therefore, the controllable semiconductor switches T1, T2, T3, T4, T5, and T6 of the machine converter 6 and the power converter 4 are physically integrated into a single centralized power electronics component 15.

[0052] The component 15 is also commonly referred to as an integrated power module (IPM) and has a single, integrated housing. The controllable semiconductor switches T1 and T2 configured for the power converter 4 are referred to as first semiconductor switches within the scope of this specification, while the controllable semiconductor switches T3, T4, T5, and T6 configured for the machine converter 6 are referred to as second semiconductor switches. Each of these controllable semiconductor switches is connected in a known manner to an anti-parallel freewheeling diode D1...D6.

[0053] Therefore, in the power electronics assembly 15, the first semiconductor switches T1 and T2 are connected to form half-bridge 7 of the power converter 4, while the second semiconductor switches T3, T4, T5, and T6 are connected to form the first and second half-bridges 10 and 12 of the machine converter 6. Since all half-bridges 7, 10, and 12 in the power electronics assembly 15 are identical, the half-bridge 7 of the power converter 4 is the same as the half-bridges 10 and 12 of the machine converter 6. Figure 2 As also shown, the power converter 4 consists of only this single half-bridge 7, which is another difference between the inverter 2 of this invention and the prior art. According to the prior art, in the case of single phase, diode rectifiers with two half-bridges are usually used as power converters.

[0054] Upon closer inspection, the half-bridge 7 of the power converter 4 consists of an upper and a lower power converter branch 7a, 7b, which are interconnected at a common first input node 8 and connected to phase L of the power supply network 1. It should be noted that the center point 16 can be understood as the second input node, since the neutral line N of the power supply network 1 is connected to this center point. The upper power converter branch 7a connects the first input node 8 to the positive terminal 17 of the DC voltage or the voltage intermediate circuit 5 via at least one of the first semiconductor switches T1 and T2 (upper controllable semiconductor switch T1), and the lower power converter branch 7b connects the first input node 8 to the negative terminal 18 of the DC voltage or the voltage intermediate circuit 5 via at least one of the first semiconductor switches T1 and T2 (lower controllable semiconductor switch T2).

[0055] like Figure 2 As shown, two corresponding semiconductor switches [T1, T2], [T3, T4], and [T5, T6] from the six semiconductor switches T1...T6 are connected in series in the power electronics assembly 15 to form one of the three half-bridges 7, 10, and 12. However, the half-bridges 7, 10, and 12 are not connected within the power electronics assembly 15, but rather outside of it.

[0056] Figure 3a An alternative embodiment of the power electronics 15 is shown, in which the three half-bridges 7, 10, 12 are interconnected in the assembly 5 on the positive terminal 17 side, i.e., the collector pins of the upper semiconductor switches T1, T3, T5. Here, the power electronics 15 can be, for example, one of the power modules FS25R12W1T4 or FS25R12W1T7P_B11 manufactured by Infineon Technologies, or one of the power modules SK35GD12T4ET or SKiiP11AC126V10 manufactured by Semikron Technologies.

[0057] Figure 3bAnother alternative embodiment of the power electronics 15 is shown, in which the three half-bridges 7, 10, 12 are already interconnected in the assembly 5 on the positive and negative sides, i.e., on one hand, the collector pins of the upper semiconductor switches T1, T3, T5, and on the other hand, the emitter pins of the lower semiconductor switches T2, T4, T6. Here, the power electronics 15 can be, for example, one of the power modules FS3L25R12W2H3_B11 or FS150R17N3E4_B11 manufactured by Infineon Technologies, or one of the power modules F1126PA025M7-L826F09, V23990-K238-F40, V23990-P708-F40-PM, or V23990-P829-F08x manufactured by Weike Electronics.

[0058] Figure 2a A variant embodiment of the frequency converter 2 of this invention is shown, which enables operation on a three-phase power supply network 1a. Here, a three-phase power filter 28a is pre-installed. In this variant, the power converter 4a is three-phase, corresponding to the number of phases L1, L2, L3 of the power supply network 1a. It is therefore composed of three identical half-bridges 7, 7', 7''. Each of these half-bridges 7, 7', 7'' consists of an upper and a lower power converter branch 7a, 7b, and has an input node 8, 8', 8'' that connects the upper and lower power converter branches 7a, 7b of the respective half-bridges 7, 7', 7'' to each other, and to a corresponding phase L1, L2, L3 of the three-phase power supply network 1a. The upper power converter branch 7a of each half-bridge 7, 7', 7'' connects the corresponding input nodes 8, 8', 8'' to the positive terminal 17 of the DC voltage via an upper controllable semiconductor switch T1, T7, T9 of the first semiconductor switch. Correspondingly, the lower power converter branch 7b of each half-bridge 7, 7', 7'' connects to the negative terminal 18 of the DC voltage via a lower controllable semiconductor switch T2, T8, T10 of the first semiconductor switch.

[0059] Therefore, the power electronics component 15a integrates five identical half-bridges, namely 10 semiconductor switches T1...T10, of which two half-bridges 10 and 12 constitute the machine converter 6, and the remaining three half-bridges 7, 7' and 7'' constitute the power converter 4a.

[0060] Figure 2bA variant embodiment of the frequency converter 2 of this invention is shown, which also enables operation on a three-phase power supply network 1a. However, the power converter 4b in this variant is two-phase. It consists of a first half-bridge 7 with a first input node 8 and a second half-bridge 7'' with a second input node 8''. Therefore, the power electronics assembly 15b integrates four identical half-bridges, namely eight semiconductor switches T1...T8, where two half-bridges 10, 12 constitute the machine converter 6 and the remaining two half-bridges 7, 7'' constitute the power converter 4a.

[0061] The first input node 8 is connected to the first phase L1 of the power grid 1a, while the second input node 8'' is connected to the second phase L3 of the power grid 1a. Additionally, the inverter 2 has a third input node 8', which is connected on one hand to the center point 16 of the voltage intermediate loop 5 and on the other hand to the third phase L2 of the power grid 1a. Therefore, in this variant embodiment, the machine converter 6 and the power converter 4b have the same topology. This inverter 2 is particularly cost-effective and compact because it can replace a conventional full inverter with six half-bridges with only four half-bridges 7, 7'', 10, and 12.

[0062] exist Figure 4 The diagram illustrates another variation of the inverter 2 of this invention, which includes a single-phase power converter 4. The characteristic feature is that the half-bridges 7, 10, and 12 each include not just one, but two series-connected controllable semiconductor switches T1...T6, T1'...T6' in each branch 7a, 7b, 10a, 10b, 12a, 12b. Between the two series-connected controllable semiconductor switches, there are connection points 19a, 19b, 22a, 22b, 25a, and 25b respectively. From these connection points, bridging wires 20a, 20b, 23a, 23b, 26a, and 26b are connected to center point 16 via center point diodes Dm1...Dm6 oriented towards the positive potential direction. This allows the potential at center point 16 in the machine inverter 6 to be applied to the first or second output interfaces 14a, 14b in such a way that the interconnected inner semiconductor switches T3', T4' or T5', T6' are in a conductive state, while the outer semiconductor switches T3', T4' or T5', T6' connected to the positive or negative terminals 17, 18 are blocked. Therefore, three different potentials or voltage levels can be switched to the first or second output interfaces 14a, 14b, thus the inverter 2 has an eight-switch, three-way, and three-level topology. Therefore, the inverter 2 of this invention does not necessarily have to be implemented using only a two-level half-bridge. More precisely, it can also be implemented using a multi-stage (multi-level) half-bridge.

[0063] The power electronics assembly 15 also integrates all the controllable semiconductor switches T1...T6, T1'...T6' of the power converter 4 and the machine converter 6, wherein the half-bridges 7, 10, and 12 are also interconnected in the power electronics assembly 15 at the positive terminal 17, the negative terminal 18, and the center point 16.

[0064] Figure 4 The inverter 2 shown in the diagram, with its additional controllable semiconductor switches T1'...T6 and center point diodes DM1...Dm6, can also be applied in a similar manner. Figure 2a and 2b In the variant scheme.

[0065] Figure 5 In addition to the inverter 2, an equivalent circuit diagram of the machine filter 29a of this invention, arranged between the inverter and the multiphase motor 3, is also shown. The machine filter consists of two inductors (coils) 30a and 30b and two capacitors (capacitors) 31a and 31b, wherein one of the inductors 30a and 30b is respectively arranged in the first and second feed lines 32a and 32b. The two capacitors 31a and 31b connect the first and second feed lines 32a and 32b, respectively, located between the multiphase motor 3 and the corresponding inductors 30a and 30b, to the third feed line 32c. Therefore, the filter 29a forms a sinusoidal filter or dU / dt filter between the machine inverter 6 and the multiphase motor 3. In contrast, the prior art... Figure 1 In filter 29, one coil, three inductive filter elements, and three capacitive filter elements are used in each phase, and they are connected in a star or delta connection on the motor side. Therefore, filter 29a of this invention saves one-third of the filter elements.

[0066] Figure 5 The primary task of the machine filter 29a shown is to reduce the voltage edge steepness between the machine converter 6 and the connected multiphase motor 3. This reduces losses in the multiphase motor 3, lowers insulation stress in the multiphase motor 3, and improves the overall electromagnetic performance of the system. Filter elements 30a, 30b, 31a, and 31b are designed to allow modulation-based pulse pattern forming, such as space vector modulation, symmetrical sinusoidal modulation, or flat-top modulation, to be used for the operation of the machine converter 6, and the fundamental oscillations of the current and voltage of the multiphase motor 3 differ from the switching frequency of the semiconductor switches in the machine converter 6 by a decimal unit. Therefore, filter elements 30a, 30b, 31a, and 31b are not designed for establishing a resonant converter topology. Furthermore, there is no electrical isolation between the power grid 1a and the machine converter 6.

[0067] The structure of machine filter 29a can also be applied to Figure 2b The power filter 28b shown is located between the power grid 1a and the frequency converter 2. Therefore, the power filter 28b can be composed of two inductors and two capacitors. One inductor connects the first input node 8 to the first phase L1 of the power grid 1a, while the other inductor connects the second input node 8'' to the second phase L3 of the power grid 1a. One capacitor connects the first input node 8 to the third input node 8', and the second capacitor connects the second input node 8'' to the third input node 8'. In this way, compared to the typical structure of a three-phase power filter 28a, both an inductor and a capacitor are saved, and the power filter 28b becomes particularly compact and economical. The function, structure, and design of the power filter 28b are similar to those of the proposed machine filter 29a. The main objective of the power filter 28b is to meet the grid connection requirements regarding current harmonics and voltage harmonics.

[0068] It should be noted that the above description is merely illustrative for explanatory purposes and does not limit the scope of protection of this utility model in any way. Features of this utility model indicated by words such as "capable," "for example," "preferred," "optional," "ideal," "advantageous," "when necessary," and "suitable" can be considered purely optional and do not limit the scope of protection, which is determined entirely by the claims. If any element, component, process step, value, or information listed in the above description has known, similar, or foreseeable equivalents, these equivalents are included within this utility model. Similarly, this utility model also includes any changes, alterations, or modifications to the embodiments, which involve the replacement, addition, alteration, or omission of elements, components, process steps, values, or information, as long as the basic concept of this utility model remains unchanged, regardless of whether such changes, alterations, or modifications lead to an improvement or deterioration of an implementation.

[0069] While the foregoing description of the utility model lists numerous physical, non-physical, or process-related features relating to one or more specific embodiments, these features can also be applied independently of the specific embodiments, at least where they do not require the absolute presence of other features. Conversely, these features listed relating to one or more specific embodiments can be arbitrarily combined with each other and with other disclosed or undisclosed features of the illustrated or unillustrated embodiments, at least where these features are not mutually exclusive or do not cause technical incompatibility.

[0070] List of reference numerals

[0071] 1. Single-phase power supply network;

[0072] 1a Three-phase power supply network;

[0073] 2. Frequency converter;

[0074] 3. Multiphase motor;

[0075] 4. Single-phase power converter;

[0076] 4a Three-phase power converter;

[0077] 4b Two-phase power converter;

[0078] 5. Voltage intermediate circuit;

[0079] 6. Machine converter;

[0080] 7, 7', 7'' half-bridge of the power converter;

[0081] 7a Upper power converter branch;

[0082] 7b Lower power converter branch;

[0083] 8, 8', 8'' Input nodes;

[0084] 9a Upper intermediate loop branch;

[0085] 9b Lower intermediate loop branch;

[0086] 10. The first half-bridge of the machine converter;

[0087] 10a Upper machine converter branch of the first half-bridge;

[0088] 10b Lower machine converter branch of the first half-bridge;

[0089] 11 First output node;

[0090] 12. The second half-bridge of the machine converter;

[0091] 12a Upper machine converter branch of the second half-bridge;

[0092] 12b Lower machine converter branch of the second half-bridge;

[0093] 13 Second output node;

[0094] 14a First output interface;

[0095] 14b Third output interface;

[0096] 14c Second Output Interface;

[0097] 15, 15a, 15b Centralized power electronic components;

[0098] 16. Center point;

[0099] 17. First pole, positive pole;

[0100] 18 Second stage, negative electrode;

[0101] 19a and 19b are the upper and lower connection points of the half-bridge of the power converter;

[0102] The upper and lower bridging wires of the half-bridge of the 20a and 20b power converters;

[0103] 22a and 22b are the upper and lower connection points of the first half-bridge of the machine converter;

[0104] 23a, 23b Upper and lower bridging wires of the first half-bridge of the machine converter;

[0105] 25a and 25b are the upper and lower connection points of the second half-bridge of the machine converter;

[0106] 26a, 26b are the upper and lower bridging wires of the second half-bridge of the machine converter;

[0107] 28, 28a, 28b power supply filters;

[0108] 29, 29a Machine filters;

[0109] 30a and 30b inductors;

[0110] Capacitors 31a and 31b;

[0111] 32a First feeder line;

[0112] 32b Second feeder line;

[0113] 32c third feeder cable;

[0114] T1...T10, T1'...T6' Controllable semiconductor switches;

[0115] D1...D10, D1'...D6' freewheeling diodes;

[0116] Center point diodes Dm1...Dm6;

[0117] C dc Intermediate circuit capacitor.

Claims

1. A frequency converter (2) for providing a frequency and magnitude variable supply voltage for a multiphase electric machine (3) or a transformer, the frequency converter comprising: Power converter (4, 4a, 4b) with first semiconductor switches (T1, T2, T1', T2', T7...T10) for converting a single- or multiphase alternating voltage of a power supply network (1, 1a) into a direct voltage, machine converter (6) with controllable second semiconductor switches (T3, T3', T4, T4', T5, T5', T6, T6') for converting the direct voltage into a supply voltage, and a voltage intermediate circuit (5) which carries the direct voltage and which is arranged between the power converter (4, 4a, 4b) and the machine converter (6) and which is formed by an upper intermediate circuit branch (9a) and a lower intermediate circuit branch (9b) which are connected to one another at a common center point (16), said upper intermediate circuit branch (9a) connecting the center point (16) to a first pole (17) of the voltage intermediate circuit (5) by means of at least one upper capacitor, and said lower intermediate circuit branch (9b) connecting the center point (16) to a second pole (18) of the voltage intermediate circuit (5) by means of at least one lower capacitor, characterized in that the machine converter (6) is formed exclusively by two identical half-bridges which contain the second semiconductor switches (T3, T3', T4, T4', T5, T5', T6, T6') for providing a first phase of the supply voltage at a first output interface (14a) and a second phase of the supply voltage at a second output interface (14b), wherein the machine converter (6) is provided for providing the center point (16) of the voltage intermediate circuit (5) at a third output interface (14c), and the power converter (4, 4a, 4b) is formed by several half-bridges which are formed identically to the half-bridges of the machine converter (6) and contain the first semiconductor switches (T1, T2, T1', T2', T7...T10), and the first and second semiconductor switches are physically integrated in one single centralized power electronics assembly (15, 15a, 15b).

2. The frequency converter (2) according to claim 1, characterized in that: In the power electronics assembly (15, 15a, 15b) exactly three, four or five identical, independent half-bridges are integrated, wherein within the power electronics assembly (15, 15a, 15b) the first semiconductor switches (T1, T2, T1', T2', T7...T10) are connected as half-bridges for the power converter (4, 4a, 4b) and the second semiconductor switches (T3, T3', T4, T4', T5, T5', T6, T6') are connected as half-bridges for the machine converter (6).

3. The frequency converter (2) according to claim 1 or 2, characterized by: The power converter (4) is formed by one half-bridge which is formed by an upper and a lower power converter branch (7a, 7b) and has a first input node (8) which connects the upper and lower power converter branches (7a, 7b) to each other and is provided for connection to a first conductor of the single-phase power supply network (1), wherein the upper power converter branch (7a) connects the first input node (8) to a first pole (17) of the DC voltage by means of at least one upper controllable semiconductor switch of the first semiconductor switches (T1, T2, T1', T2', T7...T10) and the lower power converter branch (7b) connects the first input node (8) to a second pole (18) of the DC voltage by means of at least one lower controllable semiconductor switch of the first semiconductor switches (T1, T2, T1', T2', T7...T10).

4. The frequency converter (2) according to claim 1 or 2, characterized by: The power converter (4a, 4b) is formed by two or three half-bridges, and each of these half-bridges is formed by an upper and a lower power converter branch (7a, 7b) and has an input node which connects the upper and lower power converter branches (7a, 7b) of the respective half-bridge to each other and is provided for connection to one of the phases (L1, L2, L3) of the three-phase power supply network (1a), wherein the upper power converter branch (7a) of each half-bridge connects the respective input node to a first pole (17) of the DC voltage by means of at least one upper controllable semiconductor switch of the first semiconductor switches (T1, T2, T1', T2', T7...T10) and the lower power converter branch (7b) of each half-bridge connects the respective input node to a second pole (18) of the DC voltage by means of at least one lower controllable semiconductor switch of the first semiconductor switches (T1, T2, T1', T2', T7...T10).

5. The frequency converter (2) according to claim 4, characterized in that: The power converter (4b) is formed by a first half-bridge with a first input node which is provided for connection to a first phase (L1) of the three-phase power supply network (1a) and by a second half-bridge with a second input node which is provided for connection to a second phase (L3) of the three-phase power supply network (1a), and the power converter (4b) is provided for providing a third input node which is connected to the center point (16) of the voltage intermediate circuit (5) and is provided for connection to a third phase (L2) of the three-phase power supply network (1a).

6. The frequency converter (2) according to claim 3, characterized in that: The center point (16) of the voltage intermediate circuit (5) forms the second input node and is provided for connection to a second conductor of the single-phase power supply network (1).

7. The frequency converter (2) according to claim 1 or 2, characterized by: Each of the half-bridges of the machine converter (6) consists of an upper and a lower machine converter branch, wherein the upper and lower machine converter branches of a first half-bridge of the two half-bridges are connected to each other at a common first output node (11) and to a first output interface (14a), and the upper and lower machine converter branches of a second half-bridge of the two half-bridges are connected to each other at a common second output node (13) and to a second output interface (14b), wherein the upper machine converter branch of the first half-bridge and the upper machine converter branch of the second half-bridge connect the respective output node (11, 13) to a first pole (17) of the DC voltage via at least one upper controllable semiconductor switch of the second semiconductor switches (T3, T3', T4, T4', T5, T5', T6, T6'), and the lower machine converter branch of the first half-bridge and the lower machine converter branch of the second half-bridge connect the respective output node (11, 13) to a second pole (18) of the DC voltage via at least one lower controllable semiconductor switch of the second semiconductor switches (T3, T3', T4, T4', T5, T5', T6, T6').

8. The frequency converter (2) according to claim 1 or 2, characterized by: The half-bridge comprises in each branch two controllable semiconductor switches in series, between which there is a connection point (19a, 19b, 22a, 22b, 25a, 25b) from which a bridge conductor (20a, 20b, 23a, 23b, 26a, 26b) is connected to the center point (16) via a diode (Dm1...Dm6) oriented in the direction of the positive potential.

9. The frequency converter (2) according to claim 3, characterized in that: The center point (16) of the voltage intermediate circuit (5) forms a second input node and is provided for connection to the neutral line (N) of the single-phase power supply network (1).

10. Arrangement consisting of a frequency converter (2) according to any one of claims 1 to 9 and a multiphase electric machine (3) or transformer, wherein the multiphase electric machine (3) or transformer is supplied in operation by the frequency converter and is connected via a first feed line (32a) to the first output interface (14a), via a second feed line (32b) to the second output interface (14b) and via a third feed line (32c) to the third output interface (14c).

11. The setting unit according to claim 10, characterized in that: Between the frequency converter (2) and the multiphase electric machine (3) or transformer a machine filter (29a) is arranged, which consists of two inductors (30a, 30b) and two or three capacitors, wherein one inductor is arranged in the first feed line (32a) and the other inductor is arranged in the second feed line (32b), and wherein one capacitor connects the first feed line (32a) and a second of the capacitors connects the second feed line (32b) each between the multiphase electric machine (3) or transformer and the respective inductor (30a, 30b) to the potential of the voltage intermediate circuit (5). Each of the half-bridges of the machine converter (6) consists of an upper and a lower machine converter branch, wherein the upper and lower machine converter branches of a first half-bridge of the two half-bridges are connected to each other at a common first output node (11) and to a first output interface (14a), and the upper and lower machine converter branches of a second half-bridge of the two half-bridges are connected to each other at a common second output node (13) and to a second output interface (14b), wherein the upper machine converter branch of the first half-bridge and the upper machine converter branch of the second half-bridge connect the respective output node (11, 13) to a first pole (17) of the DC voltage via at least one upper controllable semiconductor switch of the second semiconductor switches (T3, T3', T4, T4', T5, T5', T6, T6'), and the lower machine converter branch of the first half-bridge and the lower machine converter branch of the second half-bridge connect the respective output node (11, 13) to a second pole (18) of the DC voltage via at least one lower controllable semiconductor switch of the second semiconductor switches (T3, T3', T4, T4', T5, T5', T6, T6'). The half-bridge comprises in each branch two controllable semiconductor switches in series, between which there is a connection point (19a, 19b, 22a, 22b, 25a, 25b) from which a bridge conductor (20a, 20b, 23a, 23b, 26a, 26b) is connected to the center point (16) via a diode (Dm1...Dm6) oriented in the direction of the positive potential. The center point (16) of the voltage intermediate circuit (5) forms a second input node and is provided for connection to the neutral line (N) of the single-phase power supply network (1).

10. Arrangement consisting of a frequency converter (2) according to any one of claims 1 to 9 and a multiphase electric machine (3) or transformer, wherein the multiphase electric machine (3) or transformer is supplied in operation by the frequency converter and is connected via a first feed line (32a) to the first output interface (14a), via a second feed line (32b) to the second output interface (14b) and via a third feed line (32c) to the third output interface (14c). Between the frequency converter (2) and the multiphase electric machine (3) or transformer a machine filter (29a) is arranged, which consists of two inductors (30a, 30b) and two or three capacitors, wherein one inductor is arranged in the first feed line (32a) and the other inductor is arranged in the second feed line (32b), and wherein one capacitor connects the first feed line (32a) and a second of the capacitors connects the second feed line (32b) each between the multiphase electric machine (3) or transformer and the respective inductor (30a, 30b) to the potential of the voltage intermediate circuit (5).

12. The setting unit according to claim 11, characterized in that: The machine filter (29a) consists of two inductors (30a, 30b) and only two capacitors, which connect one of the first and second feed lines, respectively, to the third feed line.

13. The setting unit according to claim 10, 11 or 12, comprising a frequency converter (2) according to claim 5, characterized in that: A power supply filter (28b) is arranged between the frequency converter (2) and the power supply network (la), which power supply filter consists of two inductors and two or three capacitors, wherein one of the inductors connects the first input node to the first phase (LI) of the power supply network (la) and the other inductor connects the second input node to the second phase (L3) of the power supply network, and wherein one of the capacitors connects the first input node and a second of the capacitors connects the second input node to the potential of the voltage intermediate circuit (5).

14. The setting unit according to any one of claims 10 to 12, characterized by: The multiphase electric machine (3) is a pump motor of a centrifugal pump.

15. The setting unit according to claim 13, characterized by: In the case of only two capacitors, one of the capacitors connects the first input node and a second of the capacitors connects the second input node to the third input node.

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