WO2019180159A1 - Power supply unit for operating on an electric ac network - Google Patents

Abstract

The invention relates to a power supply unit (1) for operating on an electric AC network with a specified network frequency (26). The power supply unit (1) has at least one transformer (2) with a core (3) which has an opening (4) for passing through an outer conductor (9) of the AC network as a primary conductor (5) of the transformer (2), and a secondary winding (6) is arranged on the core (3). According to the invention, a tertiary winding (7) is arranged on the core (3), a low-pass filter (8) is connected to the tertiary winding (7), and the transmission band (21) of the low-pass filter (8) comprises the network frequency (26).

Description

 Power supply unit for operation on an electrical AC mains

The invention relates to a power supply according to the preamble of claim

1 .

A power supply is also referred to in English as a power supply unit.

The power supply is neither a transducer, in particular no summation current transformer, nor a measuring transformer.

There are known power supplies or power supplies, which electrical and / or

supply electronic components of a device with energy. such

Power supply units have a transformer which, in a manner known per se, converts an electrical voltage of a primary circuit, which is fed by an electrical energy supply network or a power supply, to another voltage applied to a secondary circuit of the transformer. The power grid is an AC grid with a grid frequency.

Electricity networks, such as transnational interconnected networks, point

Operating frequencies or mains frequencies. These are specified for a specific power grid, and each set a controlled variable as well

Stability criterion. However, not only are currents at the mains frequency on the electrical conductors of the interconnected networks. For several years, more and more inverters, power converters and switching power supplies have been connected to the power grids. These are operated with switching frequencies which are usually greater than 1 kHz, often greater than 1 MHz. Due to the tight galvanic

Coupling to the power grid, there are repercussions on this, which now also spread a significant amount of high-frequency currents of different frequencies.

These high-frequency interference currents lead to disadvantageous in a power supply

Effects. High frequency currents are well transmitted by a transformer. However, these lead primarily to the fact that the laminated cores, of which the core usually consists, are excessively heated. This effect is so dominant that the high frequency parasitic currents, which on a

Electricity network are also included, significantly heating up a Cause transformers. This is a power loss, which must be dissipated in the form of heat. This leads to highly integrated

Equipment with a tight packing density leads to considerable problems and additional costs for cooling.

Furthermore, this leads to forces between the adjacent sheets of the core of the transformer, which change forces with the high frequencies, and which lead to relative movements of the individual sheets. this leads to

Vibrations of the power supply, which are also delivered as noise to the environment. In this case, volumes can be reached, which are classified as hazardous to health during long-term exposure, and special

 Make employee protection measures necessary. The vibrations could make special, vibration-damping suspensions of the transformer required.

The object of the invention is therefore to provide a power supply of the type mentioned above, with which the mentioned disadvantages can be avoided, which occur when operating on a power grid on which in addition to the power at mains frequency and high-frequency current components, a low

Has self-heating and is quiet.

This is achieved by the features of claim 1 according to the invention.

As a result, a power supply can be created, which heats only slightly when operating on a power grid with significant high-frequency current components in addition to the power at the grid frequency. This eliminates the need for expensive cooling measures. As a result, a high component density and a compact and simple construction of a network device or a device with such a network device can be achieved. Such a power supply or a corresponding device with such a power supply device has a simple structure and a long life, since the life of electronic

Assemblies usually decreases with increasing temperature.

Furthermore, such a power supply has a low noise level. The improvement in question is depending on the burden of each Electricity network with high-frequency currents different. In a comparison test in Central Europe, the noise development of the transformer according to the embodiment of the invention with the said low-pass filter could be reduced from 78 dB (A) to 42 dB (A).

From US 1 599 570 (S.M. LUKAS) is a transformer with a

Shunt branch known which on the core of the main circle a

Tertiärwicklung has, to which a capacitor is connected, however, US 1 599 570 describes no special vote of this capacitor with respect to a specific frequency. Furthermore, US 1 599 570 also mentions no negative effects due to high-frequency currents, which occur in addition to the mains frequency. In particular, US 1 599 570 does not describe any problems concerning heat and noise development.

The invention further relates to the use of an objective power supply unit for supplying power to a protective switching device.

The subclaims relate to further advantageous embodiments of the invention.

It is hereby expressly referred to the wording of the claims, whereby the claims at this point are incorporated by reference into the description and are considered to be reproduced verbatim.

The invention will be described in more detail with reference to the accompanying drawings, in which only preferred embodiments are shown by way of example. Showing:

Fig. 1 is a schematic representation of a first embodiment of a

representational power supply unit;

Fig. 2 is a schematic representation of a second embodiment of an objective power supply unit;

Fig. 3 is a schematic representation of a circuit breaker with a

representational power supply; and

Fig. 4 is a schematically illustrated frequency spectrum. 1 and 2 each show different schematic representations of a power supply unit 1 for operation on an electrical AC network with a predetermined network frequency 26, wherein the power supply unit 1 at least one

Transformer 2 having a core 3, which core 3 has an opening 4 for passing an outer conductor 9 of the AC mains as the primary conductor 5 of the transformer 2, wherein on the core 3, a secondary winding 6 is arranged, wherein on the core 3, a tertiary winding 7 is arranged , wherein a low-pass filter 8 is connected to the tertiary winding 7, and wherein a passband 21 of the low-pass filter 8 comprises the network frequency 26.

As a result, a power supply unit 1 can be created, which heats up only slightly during operation on a power grid with considerable high-frequency current components in addition to the current at the grid frequency. This eliminates the need for expensive cooling measures. As a result, a high component density and a compact and simple construction of a network device 1 or a device with such a network device 1 can be achieved. Such a power supply 1 or a corresponding device with such a power supply 1 has a simple structure and a long life, since the life

electronic assemblies usually decreases with increasing temperature.

Furthermore, such a power supply 1 has a low noise level. The improvement in question is depending on the burden of each

Electricity network with high-frequency currents different. In a comparison test in Central Europe, the noise development of the transformer 2 according to the embodiment of the invention with said low-pass filter 8 from 78 dB (A) to 42 dB (A) could be lowered.

From US 1 599 570 (S.M. LUKAS) is a transformer with a

Shunt branch known which on the core of the main circle a

Tertiärwicklung has, to which a capacitor is connected, however, US 1 599 570 describes no special vote of this capacitor with respect to a specific frequency. Furthermore, US 1 599 570 also mentions no negative effects due to high-frequency currents, which occur in addition to the mains frequency. In particular, US 1 599 570 does not describe any problems concerning heat and noise development. A power supply unit 1 is a device for connection to the electrical power supply network, which transforms the power and voltage of the power network in the necessary for the operation of electrical or electronic equipment or equipment type and height.

The power grid is an AC grid. The terms AC mains and mains can appear objectively synonymous.

The term power supply 1 is the technically common and

a restrictive name for a unit which transforms the current and voltage of the electrical AC network or energy supply network into the type and size necessary for the operation of electrical installations.

Other or alternative names for the power supply 1 are about power supply unit or power supply unit.

The subject power supply unit 1 has a transformer 2. In the subject power supply is a so-called. Trafonetzteil. This transformer 2 is a so-called mains transformer.

The subject power supply unit 1 is a passive power supply unit 1. This means that the implementation of the voltage or the current of the primary circuit or the

Primary conductor 5 to the voltage or the current of the secondary circuit or the secondary winding 6 completely or exclusively passively by means of

Transformers 2 takes place. However, the low-pass filter 8 may be constructed as an active filter or the rectifier 13 as an active rectifier.

The subject power supply 1 is not a switching power supply, although also

Switching power supplies have a transformer. However, at one

Switching power supply of the transformer primary side not operated at the mains frequency. Furthermore, the subject power supply is not an inverter or an inverter.

From an objective power supply unit 1 with a transformer 2 to

differ is a transducer or transmitter. Although both the Using the basic principle of the transformer, they must each meet different requirements, and be in completely different

Operating environments used. It can certainly be provided that both a transducer and a power supply unit 1 are arranged in one and the same device. This is also the preferred use of the subject power supply unit in a circuit breaker 12 of the case. However, this does not change the fact that they are different assemblies. It is therefore particularly preferred that the transformer 2 is not a transducer, in particular no summation current transformer.

The power supply unit 1 can be permanently installed in a device or as a stand-alone device

Subassemblies be designed with plug connections and power cable.

The power supply unit 1 has at least one transformer 2 with a core 3. The core 3 is designed in particular as a circumferentially closed or air gap-free core 3. However, it can also be provided that the core 3 has a closed main circuit or main core, as well as a shunt branch coupled thereto via an air gap, as described for example in the already mentioned US Pat. No. 1,599,570.

In particular, it is provided that the transformer is designed for a continuous operation of at least 30 VA.

The core 3 is preferably formed from stacked sheets, as is known per se. Furthermore, it is preferably provided that the core 3 is formed as a ring band core. The at least one sheet or the sheets is particularly preferably electrical sheet, which colloquially is also referred to as Trafo sheet.

The core also has a floor plan. This plan has, according to the particularly preferred first embodiments, a first section and a second section, which are each made substantially straight. These straight first and second sections are further arranged substantially parallel to each other. These straight first and second sections are again formed by curved sections, in particular substantially semicircular sections connected.

According to a second embodiment, the core 3 has a plan view which substantially equals a rectangular frame with rounded corners. This floor plan has a total of four substantially straight sections, which are each connected by 90 ° arcs.

In particular, it is provided that the core 3 has no circular plan on.

The core 3 is formed of ferromagnetic materials. By the

representational, and measures described in detail below it has been shown that no metal sheets are required, which specifically for

High frequency applications are provided or suitable. Although such sheets are available, their production is very expensive. In concrete terms, even simple and less expensive metal sheets can be used for standard transformer applications, and with these very low-loss ones

Power supplies 1 built.

The core 3 has - in a conventional manner - an opening 4 for the implementation of a primary conductor 5 of the transformer 2. It can be provided that the primary conductor 5 is guided only through the opening 4 without the core 3 or its cross-section to wrap around. Accordingly, it can be provided that the primary conductor 5 itself is not an integral part of the power supply unit 1. Preferably, and as shown in Figs. 1 and 2, but it is provided that the

Primary conductor 5 and / or a primary winding on the core 3 is arranged or this at least partially surrounds or wraps around.

On the core 3 are a secondary winding 6 and a tertiary winding. 7

arranged. These two windings 6, 7 are electrically separated from each other and arranged separately on the core 3, and wrap around the core 3 or its cross section predetermined often. However, it may be provided that both the secondary winding 6 and the tertiary winding 7 are physically close to each other or one above the other. However, the secondary winding 6 and the tertiary winding 7 have no electrical connection with each other, and are also not formed in one piece.

The secondary winding 6 is used in a conventional manner tapping a secondary voltage. The secondary winding 6 is at least indirectly connected to outputs 10 of the power supply unit 1. It can be provided that the

Secondary winding 6, in particular terminals of the secondary winding 6, is connected directly to the outputs 10 of the power supply unit 1, as shown approximately in Fig. 2. Preferably, however, it is provided that the secondary winding 6 is connected to a rectifier 13 of the power supply 1. The rectifier 13 may also include smoothing capacitors. Furthermore, a voltage regulator and / or a throttle may be part of the power supply 1.

The power supply unit 1 is for primary-side connection to an AC network or power grid, in particular a network, such as the European

Composite system, provided. Accordingly, it is preferably provided that the primary conductor 5 is an outer conductor 9 of the power grid.

The power supply unit 1 is further provided for operation with a predetermined useful frequency or a useful frequency range. It is known per se or

unavoidable, electrical equipment, which are intended for operation on AC voltage, train or provide for a particular operating frequency or useful frequency or a corresponding frequency range.

It is provided objectively that the useful frequency is a network frequency 26 of the power network. In this case, each frequency of an alternating current network can be provided. It is preferably provided that the useful frequency is 60 Hz or 50 Hz or 25 Hz or 16.7 Hz, the usual at mains frequencies 26

Fluctuation of less than one Hz are provided. The

Mains frequencies 26 are standardized and specified for individual power grids. As such, operation of one and the same power supply may be different

Mains frequencies 26 may be provided. However, since the respective voltages are different, is or about a center tap of the

Provide secondary winding 6.

It is provided that a low-pass filter 8 is connected to the tertiary winding 7 is. It can of course be provided that the inductance of the

Tertiärwicklung 7 forms part of the low-pass filter 8, or at the

Dimensioning or tuning of the low-pass filter 8 is taken into account. Thus, about the exact number of windings of the tertiary winding 8, a fine tuning of the low pass filter 8 can be made.

Fig. 1 shows a schematic representation of an appropriately designed power supply unit 1. The primary conductor 5 is part of the power supply unit 1 and has two terminals 14, which may be formed as a terminal or as a power plug. The secondary winding 6 is connected to a rectifier 13, which is connected to outputs 10 of the power supply unit 1. The

Tertiärwicklung 7 is connected to the low pass filter 8, and otherwise has no electrical connection, in particular not to one of the externally accessible terminals of the power supply unit 1, on.

Fig. 2 shows a schematic representation of a second embodiment. In this case, no rectifier 13 is located. However, a rectifier 13 and / or the further mentioned assemblies may be provided. In addition to the power supply unit 1 according to FIG. 1, the power supply unit 1 according to FIG. 2 also has a

Quaternary development 11 on. This is not electrically connected to the secondary winding 6 and / or an output 10 of the power supply unit 1 or electrically isolated from these. The quaternary winding 11 is connected to an output of the low-pass filter 8, which is connected on the input side to the tertiary winding 7.

 As a result, the effect of the low-pass filter 8 on the transformer 2 and the attenuation of high-frequency currents or of a correspondingly high-frequency flux in the core 3 can be further improved.

The low-pass filter 8 is only with the tertiary winding 7 and / or the

Quaternary winding 11 of the transformer 2 connected, but not connected to the outside. The tertiary winding 7 is therefore not a second secondary winding 6.

It is provided that a passband 21 of the low-pass filter 8, the

Usable frequency comprises, or that the low-pass filter 8 is tuned according to that the useful frequency is transmitted as free of attenuation. Since the useful frequency is the network frequency 26 of the electrical grid, is Accordingly preferably provided that the network frequency of the respective

Power network within the passband 21 of the low pass 8 is located.

4 shows a frequency spectrum of a real AC network in a highly idealized and schematic representation. Since it is a schematic representation, the axes are not scaled. In addition to a current at the network frequency 26, which is assigned the reference numeral 26, further high-frequency interference signals are shown, each of which the reference numeral 27 is assigned. Furthermore, in Fig. 4 also strongly idealized the

Filter characteristic or the attenuation curve of the low-pass filter 8, which has been assigned the reference numeral 28. This is through the

dash-dotted Lienen in a passband 21, a transition region 22 and a stopband 23 divided. In a real implementation of the

Low-pass filter 8, the attenuation curve 28 of the low-pass filter 8 will have peaks or ripples. This is familiar to the expert in the field of electrical filters.

The low-pass filter 8 should let the grid frequency through as well as possible. Usually, the range up to an attenuation of 3 dB or -3 dB is referred to as a passband. However, an attenuation of 3 dB at the line frequency has proven to be functional in practice but also less advantageous.

It is therefore preferred that the low-pass filter 8 has an attenuation of less than 1 dB at the line frequency. It can also be provided that the low-pass filter 8 has an elevation at the mains frequency.

The low-pass filter 8 is intended to short-circuit high-frequency interference signals, which are generally emitted by switching amplifiers into the power network, and thus prevent the magnetic flux in the core 3 in this frequency range. However, the switching frequencies of the switching amplifier are not standardized. typical

Switching frequencies are about 2.5 kHz, but also switching frequencies in the range of several 100 Hz or even in the range of one MHz can occur. Of course, these also cause further high-frequency harmonics.

It has proven in this regard, for a broad applicability of the power supply unit 1, as advantageous in the design and tuning of the low-pass filter 8, when the blocking region 23 of the low-pass filter 8 comprises a lower blocking frequency 24, which lower blocking frequency is at least three octaves, in particular four octaves, greater than the useful or network frequency.

With these specifications of a very low attenuation in the Nutz- or

 Mains frequency and a high attenuation above a range of more than three octaves greater than the utility or network frequency, a certain type of filter, such as Cauer, Chebyshev, Butterworth, Bessel, etc., are selected and dimensioned. In this regard, reference is made to the relevant literature.

The low-pass filter 8 can be designed as a passive filter of predeterminable order. This has particular advantages, since hiebei a simple structure is made possible, which does not require a separate power supply. The structure

corresponding low-pass filter 8 of at least one coil and / or an ohmic resistor and one or more capacitors) is the

Specialist familiar.

The low-pass filter 8 can alternatively also be designed as an active filter of predeterminable order. Although this requires an electrical supply of a

Operational amplifier, however, allows further variants of the implementation of the filter.

Furthermore, a digital filter may be provided, which, however

for example, a corresponding pC or DSP or an FPGA or a PC with appropriate software, such as LabVIEW, is required. However, digital filters allow further freedom in the determination and definition of the filter characteristic, and in known interference frequencies, the construction of particularly low-loss and quiet power supplies. 1

In this regard, according to a further, not shown embodiment, a power supply unit 1 may be provided with a current and / or voltage sensor, which is connected to a frequency analysis unit. This analyzes the occurrence of high-frequency interference on the primary conductor 5 and detects the essential frequency components. In a control loop, the filter characteristic of a correspondingly designed active or digital low-pass filter 8 then becomes corresponding adjusted or tracked.

An objective power supply unit 1 can be used per se in any electrical device. Preferably, the use is provided in devices that have little space or are arranged in cabinets, from which the heat dissipation is problematic, and also by an accumulation of a large number of such devices, the cooling problems continue to rise and also the

Noise level swells unreasonably.

Particularly preferably, it is provided that the subject power supply unit 1 is used to supply a protective switching device 12 with electrical energy.

3 shows a schematic representation of a preferred embodiment of a corresponding protective switching device 12 with an objective power supply unit 1. The protective switching device 12 is preferably a so-called molded case circuit breaker, as used in substations, for example. Such molded case circuit breakers, which are also referred to as MCCB for "Molded Case Circuit Breaker", abbreviated to be approximately below

Designation 3VA offered by Siemens.

The relevant protective switching device 12 is shown with only one outer conductor 9, wherein a predetermined number of corresponding outer conductor. 9

can be provided. In the outer conductor 9 isolating contacts 15 are arranged. The outer conductor 9 is guided as a primary conductor 5 through the power supply unit 1, and further by a current sensor 16, which is preferably designed as a Rogowski coil. The output of the current sensor 16 is connected to an evaluation and control unit 17, which is powered by the power supply unit 1 with energy. The evaluation and control unit 17 acts on an electromagnetic actuator 19, which is designed to unlatch the switching mechanism 18, which actuates the separating contacts 15 via the mechanical connection 20.

The at least one current sensor 16 is preferably used as a measuring current transformer,

preferably designed as a summation current transformer.

Claims

PATENT APPLICATIONS 1. Power supply unit (1) for operation on an electrical alternating current network with a predetermined mains frequency (26), wherein the power supply unit (1) has at least one transformer (2) with a core (3), which core (3) has an opening (4) for the implementation of an outer conductor (9) of the AC mains as a primary conductor (5) of the transformer (2), wherein on the core (3) has a secondary winding (6) is arranged, characterized in that on the core (3) has a Tertiary winding (7) is arranged that at the tertiary winding (7) a Low pass filter (8) is connected, and that a passage region (21) of the Low pass filter (8) comprises the network frequency (26). Second power supply (1) according to claim 1, characterized in that the transformer (2) is not a transducer, in particular no summation current transformer. 3. Power supply unit (1) according to claim 1 or 2, characterized in that the AC power network is a network. 4. Power supply unit (1) according to one of claims 1 to 3, characterized characterized in that the mains frequency (26) is 60 Hz or 50 Hz or 25 Hz or 16.7 Hz. 5. Power supply unit (1) according to one of claims 1 to 4, characterized characterized in that a blocking region (23) of the low-pass filter (8) comprises a lower blocking frequency (24), which lower blocking frequency is at least three octaves greater than the network frequency (26). 6. Power supply unit (1) according to one of claims 1 to 5, characterized characterized in that the secondary winding (6), in particular terminals of the secondary winding, with outputs (10) of the power supply unit (1) is connected. 7. Power supply unit (1) according to one of claims 1 to 6, characterized characterized in that the low-pass filter (8) at the mains frequency (26) a Attenuation of less than 1 dB. 8. Power supply unit (1) according to one of claims 1 to 7, characterized in that the low-pass filter (8) is connected only to the tertiary winding (7) and / or a quaternary winding (11) of the transformer (2). 9. Power supply unit (1) according to one of claims 1 to 8, characterized in that the low-pass filter (8) is designed as a passive filter of predeterminable order. 10. Power supply unit (1) according to one of claims 1 to 9, characterized in that the low-pass filter (8) is designed as an active filter of predeterminable order. 11. Power supply unit (1) according to one of claims 1 to 10, characterized characterized in that the core (3) consists of stacked sheets. 12. Power supply unit (1) according to claim 11, characterized in that the sheet is formed as an electrical sheet. 13. Power supply unit (1) according to one of claims 1 to 12, characterized characterized in that the core (3) has a floor plan, which plan has at least a first, substantially straight portion and at least a second substantially straight portion, and that the first portion is arranged substantially parallel to the second portion. 14. Power supply unit (1) according to one of claims 1 to 13, characterized characterized in that the transformer is designed for a continuous operation of at least 30 VA. 15. A protective switching device (12) with at least one current sensor (16), in particular a measuring current transformer, preferably a summation current transformer, and at least one power supply unit (1), characterized in that the power supply unit (1) as a power supply (1) according to one of claims 1 to 14 is formed. 16. Use of a power supply unit (1) according to one of claims 1 to 14 for the power supply of a protective switching device (12).