WO2006039976A1

WO2006039976A1 - Voltage divider

Info

Publication number: WO2006039976A1
Application number: PCT/EP2005/009858
Authority: WO
Inventors: Jochen Ermisch; Axel Georgi
Original assignee: Duromer Kunststoffverarbeitungs- Gmbh
Priority date: 2004-10-16
Filing date: 2005-09-14
Publication date: 2006-04-20
Also published as: DE102004050469A1

Abstract

The invention relates to a voltage divider (1) provided with at least one high voltage resistor (2) and at least one low voltage resistor (3) for producing a low voltage (U2) and a high voltage at a predefined transmission ratio, wherein the transmission ratio is independent of frequency within a frequency range that is as wide as possible, wherein the voltage divider can be used within a frequency range which is as large as possible within predefined error limits, particularly for measuring purposes. According to the invention, said voltage divider is provided with a compensation network (14) comprising an end-sided and voltage-sided output contact (15).

Description

voltage divider

The present invention relates to a voltage divider having at least one high-voltage resistor and at least one undervoltage resistor for generating an undervoltage and a high voltage in a predetermined transmission ratio. The invention particularly relates to a generic ohmic voltage divider.

Such voltage dividers are known and widely used in particular for voltage measurement in medium and high voltage installations. For example, EP 0 815 454 describes a voltage converter with a generic voltage divider for measuring the voltage of medium and high voltage systems with a combined arrangement of resistive divider resistor and means for compensating electromagnetic environmental influences. In this case, the means for compensating electromagnetic environmental influences are shielding electrodes which surround the resistive divider resistor.

A particularly frequent application of such voltage dividers in high and medium voltage engineering is the implementation of precise measurements, for example for the purpose of monitoring. In particular, in the drive technology, such. B. in the

Magnetic levitation system Transrapid, high demands made on the error of the voltage transfer ratio. According to these requirements, it is crucial to comply with specifications both for the magnitude error and for the angle of error, ie the phase shift, over a wide frequency range. Often very close

Error limits over an extremely wide frequency range, for example, from 0 to 10,000 Hz, given. In contrast, the known voltage dividers have a frequency response due to the environmental influences, which are in particular due to the capacitances and properties of shielding electrodes, which ensures compliance with the predetermined error limits with respect to magnitude and phase only for a relatively narrow frequency range, for example from 50 to 200 Hz , However, this is completely insufficient for the mentioned applications of the technology.

In addition, the known voltage divider due to the o. G. Environmental influences a high production spread of the individual voltage divider of a production series with each other. This is also very disadvantageous both from the user's point of view as well as from the manufacturer's point of view.

Another generic voltage divider is disclosed in EP 1 018 024 B1 and has the same shortcomings as described above.

The object of the present invention is therefore to design a generic voltage divider such that its transmission ratio is frequency-independent in the widest possible frequency range, so that the voltage divider can be used in the largest possible frequency range within predetermined error limits, in particular for measuring purposes.

According to the invention, this object is achieved in that a generic voltage divider has a parallel to the undervoltage resistor compensation network with a ground-side and a voltage-side output contact. The compensation network eliminates the parasitic resistors and capacitors that are detrimental to the frequency response of the voltage divider over a wide frequency range, depending on the choice of the compensation network. By doing that Compensating network to the undervoltage resistor is connected in parallel, it can be easily added to the voltage divider without a complete re-design of the voltage divider is required. Instead, the undervoltage is simply tapped on the ground-side and the voltage-side output contact of the compensation network according to the invention instead of directly on the undervoltage resistor according to the prior art.

In an embodiment of the voltage divider according to the invention it is provided that the transmission ratio via a

Frequency range from 0 to about 1000 Hz with respect to measuring purposes given error limits for magnitude and phase is made constant. Compared with the conventional voltage dividers, whose transmission ratio only within a frequency interval of 0 to 200 Hz within suitable measurement limits error margins, the assurance of a substantially constant transmission ratio over the opposite very wide frequency range from 0 to about 1000 Hz for many applications of great Use. In particular, many measurement tasks within this frequency interval can be performed with high precision.

The voltage divider according to the invention is further improved if the transmission ratio over a frequency interval of 0 to about 10,000 Hz with respect to measurement purposes predetermined error limits for magnitude and phase is made constant. As a result, the applicability of the voltage divider according to the invention is significantly extended, so that even applications that require the highest precision, such. B. the drive technology or more specifically the magnetic levitation, can be realized with the voltage divider according to the invention. - A -

If according to a special embodiment of the invention, the compensation network contains only passive components, there is the advantage that the compensation network can resort to essentially conventional passive filter elements. These are widely used and readily available. In particular, the use of exclusively passive components results in a particularly cost-effective production of the voltage divider according to the invention.

In a special embodiment of the voltage divider according to the invention, the compensation network contains exclusively capacitances and ohmic resistances. By combining capacitances and ohmic resistors, it is possible in the compensation network according to the invention to use RC low-pass filters, RC high-pass filters, RC bandpass filters, RC bandstop filters, RC all-pass filters of any desired order, alone or networked.

The absence of the use of inductors, so coils, this leads on the one hand to a reduction in the dimensions of the compensation network as well as a reduction in weight. In addition, cost savings are possible by saving especially for low frequencies otherwise required large and expensive coils.

A special embodiment of the voltage divider according to the invention which is particularly suitable for compensation in a frequency range up to 1,000 Hz is characterized in that the compensation network has at least one three-pole input node, three-pole central node and three-pole output node, the input node being short-circuited to the voltage side of the negative resistance a first ohmic resistance is grounded and connected via a second resistor to the center node, the center node is also grounded via a third ohmic resistance and connected to the third ohmic resistor in series first capacitor and shorted to the output node, and the

Output node is also grounded via a second capacitance and connected to a voltage-side network output. With the compensation network according to the invention, advantageously, the first ohmic resistance influences the transmission ratio at low frequencies, at high frequencies it is influenced by the second capacitance, and finally at medium frequencies the second ohmic resistance, the third ohmic resistance and the first capacitance influence the second ohmic resistance transmission ratio. A particular advantage of this embodiment is the comparatively simple construction of the compensation network.

Especially for the compensation in an even larger frequency range, z. B. to 10,000 Hz, provides a variant of the voltage divider according to the invention, that between the center node and the output node, a double-T filter is connected. In this case, the known per se properties of the double-T filter, z. B. its effect as a band-stop filter, are used advantageously. Due to the circuit topology of the double-T filter, another node is led to the signal ground, in which further components or circuits can be installed.

It is particularly advantageous embodiment of the invention, when the double-T filter from a first T-filter whose signal line contains a fourth ohmic resistance and a fifth ohmic resistance and from its intermediate node in the direction of the signal ground one after the other, a capacitance and an ohmic resistance in row are connected, and from a second T-filter whose signal line contains capacitances and whose intermediate node in the direction of the signal ground in parallel, a capacitance and an ohmic resistance are connected. The first T-filter is used for the correction of low frequencies and the second T-filter for the correction of high frequencies.

According to another advantageous embodiment of the voltage divider according to the invention, the compensation network comprises a chain conductor whose elements preferably each comprise two ohmic resistors and one capacitor. The chain conductor also serves to correct the frequency response to ensure a transmission ratio of the voltage divider which is as constant as possible in terms of magnitude and phase. The chain conductor is particularly advantageous because of its internal symmetry.

In a special embodiment of the voltage divider according to the invention, the chain conductor has an input element consisting of an ohmic resistance, which is short-circuited with the voltage side of the sub-resistance. The input element serves to correct the transmission ratio at low frequencies.

The object underlying the invention is likewise achieved by a method for improving an ohmic voltage divider according to the invention, wherein a frequency response of the ohmic voltage divider is first determined according to the invention, then a compensation flag is calculated with a ground-side and a ground-facing output contact on the basis of the determined frequency response, and finally the calculated

Compensation network manufactured and installed in the voltage divider. This procedure ensures that an optimal compensation network is determined for each individual voltage divider becomes. This is an invaluable advantage, especially with regard to the production spread observed in practice, which occurs in split batches. The calculation of the compensation network on the basis of the determined frequency response can be carried out using the filter design methods known to the person skilled in the art. The computation may relate to the complete circuit topology as well as be limited to the computation of parameters such as the values for capacitances and ohmic resistances of a given circuit topology.

A particularly favorable in terms of manufacturing and logistics variant of the method according to the invention provides that a plurality of frequency responses are determined at different voltage dividers that the determined frequency responses are classified in a predetermined number of groups similar frequency response that a compensation network is calculated for each group and then the calculated compensation network is prefabricated as a compensation network module. A suitable group formation can be done with known mathematical methods such. As classification by neural networks.

Since it has been found in practice that often only a limited, discrete set of typical frequency responses occurs within the production spread, a significant reduction of the type diversity can be achieved with this procedure while maintaining predetermined error limits. The cost / benefit ratio can thus be optimized.

In an embodiment of the method according to the invention, the determined frequency response is assigned to a group with as similar a frequency response as possible and the compensation network module belonging to the assigned group is installed in the voltage divider. Thus, after the frequency response of a single voltage divider has been measured, it is assigned to the appropriate group. The group then selects the compensating network compensation module which is already prefabricated. The equipment of voltage dividers with the compensation network according to the invention can thus be added with relatively little effort to the existing production process of the voltage divider.

In a further development of the method according to the invention, the frequency response determined is a linear superimposition of several

Assigned compensation network modules. As a result, the compensation network modules can be used in the sense of a mathematical basis, which are suitably electrically combined with each other. In the case of a small logistical effort, the correction is thereby further optimized.

The invention will be described by way of example in a preferred embodiment with reference to a drawing, wherein further advantageous details are shown in the figures of the drawing.

Functionally identical parts are provided with the same reference numerals.

The figures of the drawing show in detail:

Fig. 1 shows a schematic structure of the structure of a voltage divider according to the prior art

2 simplified simplified circuit diagram of the voltage divider of FIG. 1 Fig. 3 circuit diagram of the voltage divider according to the invention with

Compensation network

Fig. 4 circuit diagram of another embodiment of the voltage divider according to the invention with Kompensationsnetzwerk

Fig. 5 circuit diagram of a third embodiment of the voltage divider according to the invention

Fig. 6 flowchart of the inventive method for

Improvement of a voltage divider according to the invention.

In Fig. 1, a voltage divider 1 consists of a

High voltage resistor 2 and an undervoltage resistor 3.

The high-voltage resistor 2 is surrounded by shielding electrodes 4.

The undervoltage resistor 3 is surrounded by shielding electrodes 5.

The shielding electrodes 4, 5 may be conductive or semiconducting. Between the high voltage resistor 2 and the

Shielding electrodes 4 create capacitances 6. The capacitances 6 are determined by the geometric conditions and their value fluctuates within a production batch of voltage dividers for technological reasons. Accordingly, capacitances 7 arise between the high-voltage resistor 2 and the shielding electrodes 5. In addition, a capacitance 7 is formed between the undervoltage resistor 3 and the shielding electrodes 5.

At a high voltage input 8 high voltage is applied to the voltage divider 1. At an earth-side and a voltage-side output contact 9, 10, the undervoltage U2 can be tapped off. The voltage divider 1 is connected to the earth 11. FIG. 2 shows an equivalent circuit diagram of the voltage divider 1 from FIG. 1. Therein, the high-voltage resistor 2 is replaced by upper voltage partial resistors 12. The capacitors 6, 7 of the shielding electrodes 4, 5 are shown as capacitors 6, 7. The high voltage resistor 3 is replaced by the lower voltage part resistors 13.

The capacitors 6, 7 are connected to the upper voltage part resistors 12 and the lower voltage part resistors 13 in the form of a chain conductor. In this case, the members of the chain conductor each comprise a high-voltage partial resistance 12 and a capacitor 6 or an undervoltage sub-resistor 13 and a capacitor 7.

Due to the fact that the ohmic divider is actually a mixed RC divider in accordance with this simplified equivalent circuit diagram, the transmission ratio of the voltage divider becomes frequency-dependent and load-dependent. This results in the consequence of a frequency dependence of the error behavior. This is unacceptable for many applications, especially in the field of drive technology.

The simplified equivalent circuit diagram of a generic voltage divider shown here serves merely for the theoretical, model-based explanation of the empirically observed frequency dependence of the transmission ratio of a real voltage divider. A closer look would lead to a further completed equivalent circuit of a voltage divider, which has even more capacity along the

Upper voltage resistor 2 and the undervoltage resistor 3 due to the shielding electrodes 4, 5 form. In addition, the ohmic resistances of the shielding electrodes 4, 5 would have to be considered be. In any case, the components included in the model additionally vary due to technological influences. It follows from all this that the voltage dividers of a production series are subject to a large variation in the frequency response and, associated therewith, the transmission ratio at a given frequency.

FIG. 3 shows the equivalent circuit diagram of the voltage divider from FIG. 2 according to the invention, supplemented by a compensation network 14. The compensation network 14 is connected in parallel to the ground-side output contact 9 and the voltage-side output contact 10 of the voltage divider 1. Das

Compensating network 14 has an input node 16, a three-pole center node 17 and a three-pole output node 18 between the voltage-side output contact 10 of the voltage divider 1 and the voltage-side network output 15. The input node 16 is connected to the voltage-side output contact of the voltage divider 1, to a resistor R8 and to a resistor R9. The center node 17 is connected to the resistor R9, the resistor R10 and to the output node 18. The output node 18 is connected on the one hand to the central node 17, on the other hand to the voltage-side network output 15 and the capacitor C8. Earth side, the resistor R8, the capacitances C7 and C8 are each connected to the earth 11.

In operation, with the resistor R8, the transmission ratio at low frequencies and with the capacitance C8, the transmission ratio at high frequencies is affected. The ohmic resistors R9, R10 and the capacitance C7 influence the middle frequencies. As a result of this simple combination, a voltage divider according to the invention is proposed in a frequency range which is very wide compared with the prior art, for example up to 1,000 Hz. which has a substantially constant transmission ratio within measurement and error limits given for measurement purposes.

4, the ohmic voltage divider according to the schematic model from FIG. 2 is another variant of the invention

Compensation network 14 shown supplemented. Compared to the compensation network 14 shown in FIG. 3, the compensation network 14 shown in FIG. 4 differs in that a double-T filter 19 is connected between the center node 17 and the output node 18 of the compensation network 14.

The double-T filter 19 consists of the ohmic resistors R11, R12 and the capacitances C11 and the resistor R14. In this case, the aforementioned elements form a first T-filter 20 of the double-T filter 19. Here, the ohmic resistor R11 is connected to the central node 17 and the ohmic resistor R12 connected to the output node. From the intermediate node 21 of the first T-filter 20 of the double T-filter 19 is connected in series, the capacitance C11 and the resistor R14 to ground 11 from.

The second T-filter 22 within the double-T filter 19 consists of the capacitances C9, C10, C13 and the resistor R13. The capacitances C9, C10 form the connection between the center node 17 and the output node 18. Of the intermediate node 23 of the second T-filter located between the capacitances C9 and C10, on the one hand the ohmic resistor R13 and, on the other hand, the capacitor C13 connected in parallel with it 11 off.

The first T-filter 20 is used for the correction of low frequencies, the second T-filter 22 is used for the correction of high frequencies. In addition, those already in connection with the description of the Embodiment of Fig. 3 described components of the compensation network 14, the filter effect described there.

Compensation network 14 according to the invention according to FIG. 4 allows compensation to be achieved in an even larger frequency range up to about 10,000 Hz. Within this frequency range, a constant transmission ratio of the voltage divider 1 with great advantage for the applications is ensured within error limits suitable for measurement purposes.

In Fig. 5, a third preferred embodiment of the voltage divider according to the invention is shown in the diagram. Again, the model equivalent circuit diagram of the known voltage divider 1 can be seen, which is supplemented by the inventive compensation network 14. In this embodiment, the compensation network 14 consists of a chain conductor. A link of the chain conductor consists of a voltage-side ohmic resistor R15, an intermediate node 24 and an earth lead 25, which is guided from the intermediate node 24 via a resistor R20 and a series-connected capacitance C12 to the earth 11. The chain ladder consists of five such chain links. Parallel to the chain conductor, the ohmic resistor R8 is connected from the input node 16 to ground 11. With this arrangement, it was also possible to achieve a voltage Ü2 which was constant in magnitude and in phase over an extremely wide frequency range.

FIG. 6 shows a flowchart which illustrates the implementation of the method according to the invention for improving an ohmic voltage divider according to the invention. As can be seen, initially in a selection step 26, a selection of voltage dividers, which are not yet equipped with a compensation network according to the invention, is made. Subsequently, for each of the selected voltage divider in the measurement procedure 27, the frequency response z. B. measured in the frequency interval from 0 to 10,000 Hz. In this case, the transmission ratio for each of the selected voltage divider over the entire frequency range from 0 to 10,000 Hz in terms of magnitude and phase is determined.

The frequency responses measured in the measurement procedure 27 are subsequently transferred to the error determination procedure 28. Within the error detection procedure 28, the frequency response is compared with the phase and frequency error specifications. At the output of the error detection procedure 28 is therefore for each voltage divider required over the entire design frequency space compensation.

In the compensation calculation procedure 29, using all known filter design algorithms for each voltage divider, the network required to compensate for the error detected in the error detection procedure 28 is determined. In doing so, the compensation calculation procedure can perform both the circuit topology and the calculation of values for the ohmic resistances and capacitances.

Finally, as part of the compensation calculation procedure 29, the required compensation network is set up on the basis of the calculated compensation.

Subsequently, the voltage divider is constructed with that in the compensation calculation procedure 29 Measure compensation network again in a measurement procedure 27 with respect to the frequency response. The measured values are again compared in an error detection procedure 28 with the error default values. The comparison values are passed to query 30, where it is decided whether the measured frequency response is acceptable or not. If this is negated 31, then a new error detection procedure 28 is performed and the above steps consisting of compensation calculation procedure 29 and subsequent measurement procedure 27 are repeated.

On the other hand, if it is found in the query 30 that the frequency response is acceptable, then a compensation board for realizing the compensation network determined during the last pass of the compensation calculation procedure 29 is built and installed in the voltage divider.

For certain voltage dividers, this may result in no compensation board being required, since in the first pass the error detection procedure 28 has already been determined that the frequency response is acceptable for the application.

Finally, a test 32 of the voltage divider is performed together with the built compensation board before delivery.

The method can be realized in a particularly cost-effective manner if, according to the invention, the frequency responses ascertained in the context of the measurement procedure 27 for a plurality of voltage dividers are grouped into groups of similar frequency response.

Subsequently, for each of these groups in the context of this compensation calculation procedure 29, the appropriate compensation network can be determined in accordance with the error specifications, and being constructed. Then a compensation board can be built for the determined compensation network of each group. The compensation boards for each of the groups can be prefabricated with great advantage as Kompensationsnetzwerkmodule already.

The method according to the invention can then be carried out for each voltage divider as described above, but at the end of the last error detection procedure 28 no compensation board has to be specially constructed, but one of the

Compensating network modules, which are already available as a board, are installed. This exploits the fact that even with a finite number of compensation networks in practice sufficient error behavior over the design frequency range is possible. This has great advantages for manufacturing, logistics and as a result the costs.

Thus, according to the invention, a method for improving an ohmic voltage divider according to the invention is proposed with which voltage dividers can be produced surprisingly simply, which lie over a very wide frequency range with respect to phase and magnitude within for carrying out measurements of suitable error limits.

LIST OF REFERENCE NUMBERS

1 voltage divider

2 high voltage resistor

3 undervoltage resistor 4 shielding electrode

5 shielding electrode

6 capacity

7 capacity

8 high-voltage input 9 earth-side output contact

10 voltage-side output contact

11 earth

12 partial voltage resistors

13 Undervoltage resistors 14 Compensation network

15 voltage side network output

16 input nodes

17 middle node

18 output nodes 19 double-T filter

20 first T-filter

21 intermediate nodes

22 second T-filter

23 intermediate nodes 24 intermediate nodes

25 earth discharge

26 selection step

27 measuring procedure

28 error detection procedure 29 Compensation calculation procedure

30 query

31 negation

32 Test R8 - R23 Resistive resistance

C7 - C16 capacity

1) 1 high voltage

U2 undervoltage

Ü2 compensated undervoltage

Claims

1. voltage divider (1) having at least one high-voltage resistor (2) and at least one undervoltage resistor (3) for generating an undervoltage (U2) and a high voltage in a predetermined transmission ratio, characterized in that it to the undervoltage resistor (3) connected in parallel compensation network (14) having a ground-side and a voltage-side output contact (15).

2. voltage divider (1) according to claim 1, d a d u r c h characterized in that the transmission ratio over a frequency interval of 0 to about 1000 Hz with respect to Meßgenau predetermined error limits for amount and phase is made constant.

3. voltage divider (1) according to claim 1 or 2, d a d u r c h characterized in that the transmission ratio over a frequency interval of 0 to about 10,000 Hz with respect to measuring predetermined error limits for magnitude and phase is made constant.

4. voltage divider (1) according to any one of the preceding claims, characterized in that the compensation network (14) contains only passive components.

5. voltage divider (1) according to one of the preceding claims, characterized in that the Compensation network (14) contains only capacitances (C7 - C16) and / or ohmic resistors (R8 - R23).

6. voltage divider (1) according to any one of the preceding claims, characterized in that the compensation network (14) voltage side at least one three-pole input node (16), a three-pole center node (17) and a three-pole output node (18), wherein

a. the input node (16) is short-circuited with the voltage side (10) of the sub-resistor (3), grounded via a first ohmic resistor (R8) and connected to the center node (17) via a second ohmic resistor (R9),

b. the central node (17) is further grounded via a third ohmic resistor (R10) and a first capacitor (C7) connected in series with the third ohmic resistor (R10) and shorted to the output node (18), and

c. the output node (18) is also grounded via a second capacitance (C8) and connected to a voltage side network output (15).

7. voltage divider (1) according to claim 6, characterized in that between the central node (17) and the output node (18), a double-T filter (19) is connected.

8. voltage divider (1) according to claim 6 or 7, characterized in that the double-T filter (19) consists of a first T-filter (20), the signal line a fourth ohmic resistance (R11) and a fifth ohmic resistance (R12) contains and from the intermediate node (21) in the direction of the signal ground (11) successively a capacitor (C11) and an ohmic resistor (R14) are connected in series, and from a second T-filter (22) whose signal line two capacitances (C9 , C10) and from the intermediate node (23) in the direction of the signal ground (11) in parallel a capacitance (C13) and an ohmic resistor (R13) are connected.

9. voltage divider (1) according to one of claims 1 to 5, d a d u r c h characterized in that the compensation network (14) comprises a chain conductor, whose members preferably each comprise two ohmic resistors (R15, R16) and a capacitor (C12).

10. voltage divider (1) according to one of claims 1 to 6, d a d u r c h characterized in that the chain conductor comprises an ohmic resistor (R8) existing input member, which is short-circuited with the voltage side of the negative resistance.

11. A method for improving a voltage divider (1) according to any one of the preceding claims, characterized in that first a frequency response of

Voltage divider (1) is determined, then a compensation network (14) with a low-side and a voltage-side output contact (15) is calculated on the basis of the determined frequency response and finally the calculated compensation network (14) and manufactured in the

Voltage divider (1) is installed.

12. The method according to claim 11, characterized in that a plurality of frequency responses at different Voltage dividers (1) are determined that the determined frequency responses are classified into a predetermined number of groups similar frequency response that a compensation network (14) is calculated for each group and then the calculated compensation network (14) as

Compensation network module is prefabricated.

13. The method of claim 12, ad d u rch characterized in that the determined frequency response of a group with the most similar frequency response is assigned and the belonging to the associated group compensation network module in the voltage divider (1) is installed.

14. The method of claim 12 or 13, d a d u r c h characterized in that the determined frequency response of a linear overlay of multiple compensation network modules is assigned.