EP0400343B1 - Stromwandleranordnung mit erhöhter Genauigkeit - Google Patents

Stromwandleranordnung mit erhöhter Genauigkeit Download PDF

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Publication number
EP0400343B1
EP0400343B1 EP90108288A EP90108288A EP0400343B1 EP 0400343 B1 EP0400343 B1 EP 0400343B1 EP 90108288 A EP90108288 A EP 90108288A EP 90108288 A EP90108288 A EP 90108288A EP 0400343 B1 EP0400343 B1 EP 0400343B1
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EP
European Patent Office
Prior art keywords
current
transformer
comparator
converter
winding
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP90108288A
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German (de)
English (en)
French (fr)
Other versions
EP0400343A1 (de
Inventor
Frank Dipl.-Ing. Herrmann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Deutsche Zaehler-Gesellschaft Nachf A Stepper & Co (gmbh & Co)
Original Assignee
Deutsche Zaehler-Gesellschaft Nachf A Stepper & Co (gmbh & Co)
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Publication date
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Publication of EP0400343A1 publication Critical patent/EP0400343A1/de
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Publication of EP0400343B1 publication Critical patent/EP0400343B1/de
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/42—Circuits specially adapted for the purpose of modifying, or compensating for, electric characteristics of transformers, reactors, or choke coils
    • H01F27/422—Circuits specially adapted for the purpose of modifying, or compensating for, electric characteristics of transformers, reactors, or choke coils for instrument transformers
    • H01F27/427—Circuits specially adapted for the purpose of modifying, or compensating for, electric characteristics of transformers, reactors, or choke coils for instrument transformers for current transformers

Definitions

  • the invention relates to a current transformer arrangement with increased accuracy, in which a comparator converter and a power converter with their primary windings are connected in series in a main circuit, in which a compensation current is fed from a secondary winding of the power converter to a winding of the comparator converter to reduce the magnetization of the core of the comparator converter and in which an indicator winding of the comparator converter emits a difference signal corresponding to the remaining magnetic flux, which is amplified and fed as a differential current to another winding of the comparator converter, the sum of the compensation current and the difference current forming the output signal, and is based on DE-Z "messtechnik" 10/68, page 242 ff.
  • Static household electricity meters must therefore have a certain DC independence. So-called precision comparison counters are used for the metrological examination and checking both in the laboratory and at the installation site, which must have a much higher accuracy than the test object.
  • the current input circuit of the test meter must not have greater measurement uncertainties in mixed current operation than in pure alternating current operation.
  • the invention has for its object to achieve a high accuracy both with alternating current and for mixed current with a cost-effective design in a current transformer arrangement of the type mentioned.
  • the magnetic effect of the direct current component of the main current is at least almost compensated for in the comparator core, so that an impermissible operating point shift due to the direct current is avoided.
  • the comparator converter then works like a direct current-free main current.
  • FIG. 1 A known current transformer arrangement is shown in FIG.
  • the primary winding 10 of a comparator converter 11 and the primary winding 12 of a power converter 13 are connected in series by a main current Ih between the terminals 14 and 15.
  • the comparator converter 11 carries a first secondary winding 16, which is loaded with a load 18, in particular an ohmic resistance, to earth.
  • a current I1 is fed to the other end of the winding 16 from a secondary winding 17 of the power converter 13 connected to earth on the other side.
  • this current is dimensioned that it causes about the same flow as the primary winding 10 as a result of the main current Ih via the secondary winding 16 in the comparator 11 via its ampere-turn number.
  • this disadvantageous influence of a direct current component of the main current Ih is to be eliminated or at least greatly reduced.
  • the main current Ih flows between the terminals 14 and 15 through the primary winding 21 of a comparator converter 22 and through the primary winding 23 of a power converter 24.
  • a magnetic field-dependent signal converter (sensor) 25 By means of a magnetic field-dependent signal converter (sensor) 25, the magnetic flux caused by the main current Ih in the core of the power converter 24 is detected.
  • the magnetic field-dependent electrical variable obtained in this way is converted via an electronic amplifier 26 and a voltage / current converter 27 into a current I3, which leads through a secondary winding 28 on the core of the comparator converter 22 to an electronic amplifier 30 which is coupled back via a resistor 29.
  • the direct current component is separated from the amplified mixed current I3 from the output of the amplifier 30 via a capacitor 31 and the alternating current component is fed to the output via an impedance 32, which is formed by an electronic amplifier 34 which is coupled against an impedance 33 in front of the output terminal A.
  • the current I3 largely compensates for the magnetic flux in the core of the comparator converter 22 caused by the main current Ih with its alternating current components and its direct current component. Due to the remaining magnetic flux, a signal is generated in an indicator winding 36, which supplies a current I4 for a secondary winding 38 via an amplifier 37.
  • This secondary winding 38 is attached and dimensioned in such a way that it counteracts the residual magnetic flux in the core of the comparator converter 22 and largely compensates for this, in accordance with the degree of amplification of the amplifier 37. Since the compensation current I3 through the secondary winding 28 also contains the DC component, this too is largely compensated for in the core of the comparator converter 22.
  • the current I4 of the winding 36 only reduces the alternating components in the magnetic flux.
  • This current I4 is also fed to the input of the amplifier 34, so that, as in FIG. 1, a signal occurs at the output terminal A, which is composed of the sum of the AC components of the currents I3 and I4 and from the primary-side control of the comparator converter 22 is independent except for a very small error.
  • the power converter 24 does not need to apply power in the actual sense here, since the energy for the compensating current I3 is supplied by the amplifier 26 and possibly the U / I converter 27.
  • the compensating current I3 is as in FIG Amplifier 26 and the U / I converter 27 generated.
  • This current I3 is fed via a winding 41 of the comparator converter 22 to the load 42 to earth, and the output signal which arises there is taken off in a DC-free manner via a separating capacitor 43 at the output terminal A.
  • the comparator converter Due to the current I3 flowing in opposite directions, the comparator converter largely compensates for the Main current Ih and the magnetic flux caused by the compensation current I3 causes the core of the comparator converter 22 to remain largely in a magnetic flux-free state, both with regard to the AC component desired for the measurement and also with regard to the generally undesirable one DC component.
  • the remaining alternating current magnetic flux (flow difference) still occurring in the comparator converter 22 is determined and converted via an amplifier 45 and a U / I converter 46 into a compensation current I4, which together with the current I3 of the secondary winding 41 leads to the output becomes.
  • the compensation current I4 thus, like in the figures above, causes the compensation of the alternating current magnetic flux in the core of the comparator converter 22 very precisely.
  • a converter suitable for a power converter 24 according to FIG. 2 or 3 can be designed in a ring with an air gap, the air gap on the one hand reducing the risk of saturation in a simple manner and on the other hand a magneto-electrical element as a signal converter (sensor) for measuring of the magnetic flux can be attached.
  • the magnetic field-dependent sensor can work using the Hall effect or take advantage of the magnetoresistive effect, that is to say a change in the electrical resistance depending on an applied magnetic field.
  • a magneto-optical effect can also be used with corresponding additional optical sensor elements.
  • FIG. 4 shows an embodiment in which the magnetic flux in the power converter 24 is largely compensated for.
  • the electrical signal from the magneto-electrical signal converter (sensor) 25 is fed to an amplifier 48, which supplies a current I5 which initially flows through a secondary winding 49 of the power converter 24.
  • the number of turns of the primary winding 23 and this secondary winding 49 and the degree of amplification of the amplifier 48 are dimensioned such that, apart from a small control error, the magnetic flux in the core of the power converter 24 is compensated for.
  • the equalizing current I5 continues to flow through a secondary winding 50 of the comparator converter 22 to the burden 42;
  • the DC-free output signal can be taken from terminal A via the isolating capacitor 43.
  • a winding 44 is further attached to the comparator core 22, which supplies an alternating current signal I4 corresponding to the residual magnetic flux in the core of the converter 22 via an amplifier 45 and a U / I converter 46, since it is at the connection point of the secondary windings 49 and 50 is fed in and flows with the burden 42, whereby a very precise compensation of the alternating current magnetic flux in the comparator converter 22 is effected.
  • FIG. 5 The embodiment of Figure 5 is largely the same as that of Figure 4 and also carries the same reference numerals for corresponding parts.
  • the comparator converter 22 is also equipped with a magnetoelectric sensor 52, which supplies the flow difference signal via an amplifier 53 and a U / I converter 54 as a corrective compensation current I6 to the connection point of the windings 49 and 50.
  • a composite current I5 + I6 thus flows to the load 42, which is also compensated for direct current at the comparator converter 22.
  • Another difference is that in the burden 42 at the output Am a mixed flow is available, which is in a very precise ratio to the primary mixed current Ih, which therefore contains a DC component.
  • the AC-free DC component can also be removed at an output Ag via an AC blocking filter 56.
  • both converters 22 and 24 need to transmit very little power, so that very small cores can be used. However, the power must be applied by the amplifiers in the case of compensated converters.
  • the new arrangement has created a current transformer arrangement with increased accuracy, in which a power converter (24) and a comparator converter (22) with their primary windings (21, 23) lie in series in a main circuit (Ih), in which the power converter (13 ) a current is generated with which the magnetic flux is compensated for at least almost to zero in the comparator converter (22), whereby according to the invention the DC component of the main current (Ih) is also detected with the aid of a magnetoelectric signal converter (25) and used for the compensation ( Fig.2).
  • the DC component can even be available in the secondary current as a precise image of the primary current (Fig. 5).

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Measurement Of Current Or Voltage (AREA)
  • Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
  • Control Of Eletrric Generators (AREA)
  • Transformers For Measuring Instruments (AREA)
  • Dc-Dc Converters (AREA)
EP90108288A 1989-06-02 1990-05-01 Stromwandleranordnung mit erhöhter Genauigkeit Expired - Lifetime EP0400343B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3918100A DE3918100A1 (de) 1989-06-02 1989-06-02 Stromwandleranordnung mit erhoehter genauigkeit
DE3918100 1989-06-02

Publications (2)

Publication Number Publication Date
EP0400343A1 EP0400343A1 (de) 1990-12-05
EP0400343B1 true EP0400343B1 (de) 1993-07-14

Family

ID=6381981

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90108288A Expired - Lifetime EP0400343B1 (de) 1989-06-02 1990-05-01 Stromwandleranordnung mit erhöhter Genauigkeit

Country Status (4)

Country Link
EP (1) EP0400343B1 (da)
AT (1) ATE91566T1 (da)
DE (2) DE3918100A1 (da)
DK (1) DK0400343T3 (da)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10311441B4 (de) * 2003-03-15 2005-03-10 Emh Elek Zitaetszaehler Gmbh & Elektronischer Elektrizitätszähler

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3783869D1 (de) * 1986-11-11 1993-03-11 Siemens Ag Flusskompensierter stromwandler.
DE3705450A1 (de) * 1987-02-20 1988-09-01 Vacuumschmelze Gmbh Stromwandler zur messung von rechteckstroemen nach dem kompensationsprinzip

Also Published As

Publication number Publication date
DE3918100C2 (da) 1992-07-16
DE59001950D1 (de) 1993-08-19
ATE91566T1 (de) 1993-07-15
DE3918100A1 (de) 1990-12-06
DK0400343T3 (da) 1993-08-23
EP0400343A1 (de) 1990-12-05

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