WO1998052054A1 - Current transformer for alternating current measurements in the low voltage range - Google Patents

Current transformer for alternating current measurements in the low voltage range Download PDF

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Publication number
WO1998052054A1
WO1998052054A1 PCT/DE1998/001295 DE9801295W WO9852054A1 WO 1998052054 A1 WO1998052054 A1 WO 1998052054A1 DE 9801295 W DE9801295 W DE 9801295W WO 9852054 A1 WO9852054 A1 WO 9852054A1
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WIPO (PCT)
Prior art keywords
winding
short
circuit
current transformer
transformer according
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PCT/DE1998/001295
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German (de)
French (fr)
Inventor
Reinhard Maier
Werner Elischer
Original Assignee
Siemens Aktiengesellschaft
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Publication of WO1998052054A1 publication Critical patent/WO1998052054A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
    • H01F38/20—Instruments transformers
    • H01F38/22—Instruments transformers for single phase ac
    • H01F38/28—Current transformers
    • H01F38/32—Circuit arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
    • G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
    • G01R15/183—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core
    • G01R15/185—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core with compensation or feedback windings or interacting coils, e.g. 0-flux sensors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
    • H01F38/20—Instruments transformers

Definitions

  • the invention relates to a current transformer for AC measurements in the low-voltage range, with a primary winding for integration into a circuit and two transformer-connected secondary windings, of which one winding is a short-circuit turn, and of which the other winding has a predetermined number of turns as a measuring winding and can be connected to evaluation electronics.
  • the object of the invention is to technically simplify a three-winding current transformer.
  • the object is achieved in that the short-circuit winding consists of a metal body on which the windings of the measuring winding are wound.
  • the metal body forms a ring made of, in particular, solid copper material.
  • the winding with a short-circuit turn is preferably designed in section as a hollow profile for receiving the second winding. In particular, it can be designed in the form of a rectangular U-profile.
  • a three-winding current transformer is realized, in which, by using a controllable short-circuit ring, the complicated secondary winding with a high number of turns, which is otherwise necessary in the case of large transmission ratios, is no longer necessary.
  • Figure 1 is a circuit diagram of a three-winding converter with associated measuring device
  • Figure 2 shows the concrete structure of a three-winding converter according to the invention.
  • W1 denotes a primary winding and W2 and W3 denote two secondary windings of a transformer current transformer.
  • the current transformer is used to measure currents in the low-voltage range, currents between 0 and 150 A being on the primary side of the transformer, for example.
  • the winding W3 is short-circuited as a short-circuit turn, while the winding W2 serves as a measuring winding with a predetermined number of turns.
  • the output signal from W2 is fed to an operational amplifier 5.
  • the operational amplifier 5 is shown in FIG. Stand 6 of 1.1 k ⁇ fed back and connected to a potentiometer 7 for offset adjustment.
  • the output A of the operational amplifier defines the corresponding measuring outputs with the associated potential measuring points M, P and N.
  • winding W2 and W3 act as a parallel connection, the flow and thus the current being divided according to their extremely different resistances. Electrically, winding W2, like winding W3, acts as a short-circuit winding, since the voltage at the input of the connected one
  • Amplifier is approximately zero.
  • the current density in the two windings W2 and W3 is approximately the same.
  • the primary current is a maximum of 150 A:
  • the winding W2 thus takes on only approximately 0.08% of the flow, while the rest is taken over by the short-circuit rings of the winding W3. This ensures that a very large gear ratio is achieved with a relatively low number of secondary turns.
  • the short-circuit winding W3 is designed as a solid short-circuit ring 10 through which a current loop as the primary winding W1 can be passed.
  • the short-circuit ring 10 forms a hollow profile and has, for example, a rectangular U-profile with associated flanks 11. In this hollow profile there is the winding W2 with the corresponding number of turns, so that a winding package 20 results.
  • the short-circuit ring 10 consists of compact copper material, whereas the winding package 20 of the second winding W2 is formed from enamel-insulated copper wire with individual turns 21. Good thermal contact between the windings W2 and W3 keeps the temperature of the two windings approximately the same. Since both windings are made of copper, the temperature coefficient of the electrical resistance is the same for both windings. Due to the approximately identical current indices in the two windings, the sharp rise in temperature in the event of overcurrent pulses in both windings has the same course. This ensures a largely temperature-independent distribution of the currents between the windings W2 and W3 and thus a low thermal error.
  • converter systems are created which can be adapted to different nominal currents by means of interchangeable, differently designed short-circuit rings 10 for the short-circuit winding W3 while the amplifier circuits remain the same. It is also possible to attach annular disks on one or both sides to an existing short-circuit ring 10 for adjusting the measuring range. Since a comparatively large number of turns of the measuring winding W3 can be applied to such a short-circuit ring 10, the accuracy during the subsequent amplification is improved.

Abstract

Known current transformers that work in accordance with the transformer principle have a primary winding for connecting to an electric circuit and two transformer-coupled secondary windings, one of which consists of a short-circuited winding, while the other is a measuring winding having a predetermined number of windings which are connected to an evaluation unit. In accordance with the invention, the short-circuited turn (W3) consists of a ring-shaped metallic body (10), around which are coiled the windings (20, 21) of the measuring winding (W2).

Description

Beschreibungdescription
Stromwandler für echselstrommessungen im NiederspannungsbereichCurrent transformers for AC measurements in the low voltage range
Die Erfindung bezieht sich auf einen Stromwandler für Wechselstrommessungen im Niederspannungsbereich, mit einer Primärwicklung zur Einbindung in einen Stromkreis und zwei transformatorisch angekoppelten Sekundärwicklungen, von denen die eine Wicklung eine Kurzschlußwindung ist, und von denen die andere Wicklung als Meßwicklung eine vorbestimmte Anzahl von Windungen aufweist und an eine Auswerteelektronik anschließbar ist.The invention relates to a current transformer for AC measurements in the low-voltage range, with a primary winding for integration into a circuit and two transformer-connected secondary windings, of which one winding is a short-circuit turn, and of which the other winding has a predetermined number of turns as a measuring winding and can be connected to evaluation electronics.
Für Strommessungen, insbesondere im Niederspannungsbereich, sind Stromwandler bekannt, die im allgemeinen zwei Wicklungen mit Primär- und Sekundärwicklung aufweisen. Aufgrund des notwendigen transformatorischen Übersetzungsverhältnisses sind solche Stromwandler vergleichsweise groß und daher aufwendig. Es sind auch sogenannte Kompensationsstromwandler bekannt und es ist weiterhin möglich, eine Strommessung im Niederspannungsbereich über einen Shunt durchzuführen.Current transformers are known for current measurements, particularly in the low-voltage range, which generally have two windings with primary and secondary windings. Due to the necessary transformer ratio, such current transformers are comparatively large and therefore expensive. So-called compensation current transformers are also known and it is also possible to carry out a current measurement in the low-voltage range via a shunt.
Daneben ist aus der WO 93/01502 AI eine Einrichtung zur Strommessung im Niederspannungsbereich nach dem transformatorischen Prinzip bekannt, bei der speziell zwei Sekundärwicklungen vorhanden sind, wobei in einer der Sekundärwicklungen gemessen wird. Derartige Anordnungen werden allgemein als „Dreiwicklungsstromwandler" bezeichnet. Ahnliche Anordnungen werden weiterhin in der EP 0 157 881 AI und der US 5 432 439 A beschrieben, wobei es bei letzterer Druckschrift auch um den Aufbau der einzelnen Wicklungen geht. Beispielsweise ist eine Wicklung als gedruckte Schaltung auf einer Platine angegeben.In addition, from WO 93/01502 AI a device for current measurement in the low-voltage range according to the transformer principle is known, in which there are specifically two secondary windings, one of the secondary windings being measured. Such arrangements are generally referred to as "three-winding current transformers". Similar arrangements are also described in EP 0 157 881 A1 and US 5 432 439 A, the latter document also relating to the structure of the individual windings. For example, a winding is printed Circuit specified on a circuit board.
Aufgabe der Erfindung ist es demgegenüber, einen Dreiwicklungsstromwandler technisch zu vereinfachen. Die Aufgabe ist erfindungsgemäß dadurch gelöst, daß die Kurzschlußwindung aus einem Metallkörper besteht, auf dem die Windungen der Meßwicklung aufgewickelt sind. Der Metallkörper bildet dabei einen Ring aus insbesondere massivem Kupfer- Material. Vorzugsweise ist die Wicklung mit Kurzschlußwindung im Schnitt als Hohlprofil zur Aufnahme der zweiten Wicklung ausgebildet. Insbesondere kann sie im Schnitt als Rechteck- U-Profil ausgebildet sein.In contrast, the object of the invention is to technically simplify a three-winding current transformer. The object is achieved in that the short-circuit winding consists of a metal body on which the windings of the measuring winding are wound. The metal body forms a ring made of, in particular, solid copper material. The winding with a short-circuit turn is preferably designed in section as a hollow profile for receiving the second winding. In particular, it can be designed in the form of a rectangular U-profile.
Mit der Erfindung ist ein Dreiwicklungsstromwandler realisiert, bei dem durch Verwendung eines ansteuerbaren Kurzschlußringes die sonst bei großen Übersetzungsverhältnissen notwendige aufwendige Sekundärwicklung mit hoher Windungszahl nicht mehr notwendig ist.With the invention, a three-winding current transformer is realized, in which, by using a controllable short-circuit ring, the complicated secondary winding with a high number of turns, which is otherwise necessary in the case of large transmission ratios, is no longer necessary.
Weitere Einzelheiten und Vorteile der Erfindung ergeben sich aus der nachfolgenden Figurenbeschreibung von Ausführungs- beispielen anhand der Zeichnung. Es zeigenFurther details and advantages of the invention result from the following description of the figures of exemplary embodiments with reference to the drawing. Show it
Figur 1 ein Schaltbild eines Dreiwicklungswandlers mit zugehöriger Meßeinrichtung undFigure 1 is a circuit diagram of a three-winding converter with associated measuring device and
Figur 2 den konkreten Aufbau eines Dreiwicklungswandlers gemäß der Erfindung.Figure 2 shows the concrete structure of a three-winding converter according to the invention.
In Figur 1 ist mit Wl eine Primärwicklung und sind mit W2 und W3 zwei Sekundärwicklungen eines transformatorischen Stromwandlers bezeichnet. Der Stromwandler dient zur Messung von Strömen im Niederspannungsbereich, wobei auf der Primärseite des Wandlers beispielsweise Ströme zwischen 0 und 150 A liegen.In FIG. 1, W1 denotes a primary winding and W2 and W3 denote two secondary windings of a transformer current transformer. The current transformer is used to measure currents in the low-voltage range, currents between 0 and 150 A being on the primary side of the transformer, for example.
Auf der Sekundärseite ist die Wicklung W3 als Kurzschlußwindung kurzgeschlossen, während die Wicklung W2 mit vorge- gebener Windungszahl als Meßwicklung dient. Das Ausgangssignal von W2 wird auf einen Operationsverstärker 5 gegeben. Der Operationsverstärker 5 ist in Figur 1 mit einem Wider- stand 6 von 1,1 kΩ rückgekoppelt und an ein Potentiometer 7 zum Offsetabgleich angeschlossen. Der Ausgang A des Operationsverstärkers definiert mit den zugehörigen Potentialmeßpunkten M, P und N die entsprechenden Meßausgänge.On the secondary side, the winding W3 is short-circuited as a short-circuit turn, while the winding W2 serves as a measuring winding with a predetermined number of turns. The output signal from W2 is fed to an operational amplifier 5. The operational amplifier 5 is shown in FIG. Stand 6 of 1.1 kΩ fed back and connected to a potentiometer 7 for offset adjustment. The output A of the operational amplifier defines the corresponding measuring outputs with the associated potential measuring points M, P and N.
Die Wicklungen W2 und W3 wirken als Parallelschaltung, wobei sich die Durchflutung und damit der Strom entsprechend ihren extrem unterschiedlichen Widerständen aufteilt. Elektrisch wirkt die Wicklung W2 ebenso wie Wicklung W3 als Kurzschluß- icklung, da die Spannung am Eingang des angeschlossenenThe windings W2 and W3 act as a parallel connection, the flow and thus the current being divided according to their extremely different resistances. Electrically, winding W2, like winding W3, acts as a short-circuit winding, since the voltage at the input of the connected one
Verstärkers annähernd Null ist. Die Stromdichte in den beiden Wicklungen W2 und W3 ist dadurch annähernd gleich.Amplifier is approximately zero. The current density in the two windings W2 and W3 is approximately the same.
Bei der Anordnung gemäß Figur 1 beträgt der Primärstrom maximal 150 A: Der Sekundärstrom in der Wicklung W2 beträgt dabei beispielsweise 7,7 mA, was bei einer Windungszahl von n2 = 15 einer Durchflutung von ca. 115 mA entspricht. Die Wicklung W2 übernimmt also nur annähernd 0,08 % der Durchflutung, während der Rest von den Kurzschlußringen der Wicklung W3 übernommen wird. Dadurch wird erreicht, daß mit einer relativ niedrigen Sekundärwindungszahl ein sehr großes Übersetzungsverhältnis erzielt wird.In the arrangement according to FIG. 1, the primary current is a maximum of 150 A: The secondary current in the winding W2 is, for example, 7.7 mA, which corresponds to a flooding of approximately 115 mA with a number of turns of n 2 = 15. The winding W2 thus takes on only approximately 0.08% of the flow, while the rest is taken over by the short-circuit rings of the winding W3. This ensures that a very large gear ratio is achieved with a relatively low number of secondary turns.
Aus Figur 2 ist ersichtlich, daß die Kurzschlußwicklung W3 als massiver Kurzschlußring 10, durch den eine Stromschleife als Primärwicklung Wl hindurchführbar ist, ausgebildet ist. Der Kurzschlußring 10 bildet ein Hohlprofil, und hat beispielsweise ein Rechteck-U-Profil mit zugehörigen Flanken 11. In diesem Hohlprofil befindet sich die Wicklung W2 mit ent- sprechenden Windungszahlen, so daß sich ein Wicklungspaket 20 ergibt.It can be seen from FIG. 2 that the short-circuit winding W3 is designed as a solid short-circuit ring 10 through which a current loop as the primary winding W1 can be passed. The short-circuit ring 10 forms a hollow profile and has, for example, a rectangular U-profile with associated flanks 11. In this hollow profile there is the winding W2 with the corresponding number of turns, so that a winding package 20 results.
Der Kurzschlußring 10 besteht aus kompaktem Kupfer-Material, wogegen das Wicklungspaket 20 der zweiten Wicklung W2 aus lackisoliertem Kupferdraht mit einzelnen Windungen 21 gebildet ist. Durch einen guten thermischen Kontakt zwischen den Wicklungen W2 und W3 wird die Temperatur der beiden Wicklungen annähernd gleich gehalten. Da beide Wicklungen aus Kupfer bestehen, ist auch der Temperaturkoeffizient des elektrischen Widerstandes für beide Wicklungen gleich. Aufgrund der annähernd gleichen Stromidchte in den beiden Wicklungen hat auch der starke Temperaturanstieg bei Überstromimpulsen in beiden Wicklungen den gleichen Verlauf. Dadurch ist eine weitgehend temperaturunabhängige Aufteilung der Ströme zwischen den Wicklungen W2 und W3 und damit ein geringer thermischer Fehler gewährleistet.The short-circuit ring 10 consists of compact copper material, whereas the winding package 20 of the second winding W2 is formed from enamel-insulated copper wire with individual turns 21. Good thermal contact between the windings W2 and W3 keeps the temperature of the two windings approximately the same. Since both windings are made of copper, the temperature coefficient of the electrical resistance is the same for both windings. Due to the approximately identical current indices in the two windings, the sharp rise in temperature in the event of overcurrent pulses in both windings has the same course. This ensures a largely temperature-independent distribution of the currents between the windings W2 and W3 and thus a low thermal error.
Mit dem beschriebenen Aufbau sind Wandlersysteme geschaffen, die durch austauschbare, unterschiedlich ausgebildete Kurz- schlußringe 10 für die Kurzschlußwicklung W3 bei gleichbleibenden Verstärkerschaltungen an verschiedene Nennströme anpaßbar sind. Es können auch an einen bestehenden Kurzschlußring 10 zur Meßbereichsanpassung ein- oder beidseitig ringförmige Scheiben angebracht werden. Da auf einem solchen Kurzschlußring 10 eine vergleichsweise hohe Anzahl von Windungen der Meßwicklung W3 aufgebracht werden können, ergibt sich eine Verbesserung der Genauigkeit bei der anschließenden Verstärkung.With the construction described, converter systems are created which can be adapted to different nominal currents by means of interchangeable, differently designed short-circuit rings 10 for the short-circuit winding W3 while the amplifier circuits remain the same. It is also possible to attach annular disks on one or both sides to an existing short-circuit ring 10 for adjusting the measuring range. Since a comparatively large number of turns of the measuring winding W3 can be applied to such a short-circuit ring 10, the accuracy during the subsequent amplification is improved.
Eine andere Möglichkeit zur Anpassung an niedrige Primärnennströme besteht darin, die Primärwicklung mit mehreren Windungen auszuführen. Schließlich können solche Systeme dadurch auch für höhere Ströme angewandt werden, daß eine Kombination mit einer primären Stromschienenshuntung realisiert wird. Another possibility to adapt to low primary nominal currents is to carry out the primary winding with several turns. Finally, such systems can also be used for higher currents by implementing a combination with a primary busbar shunt.

Claims

Patentansprüche claims
1. Stromwandler für Wechselstrommessungen im Niederspannungsbereich, mit einer Primärwicklung zur Einbindung in einen Stromkreis und zwei transformatorisch angekoppelten Sekundärwicklungen, von denen die eine Wicklung eine Kurzschlußwindung ist, und von denen die andere Wicklung als Meßwicklung eine vorbestimmte Anzahl von Windungen aufweist und an eine Auswerteelektronik anschließbar ist, d a d u r c h g e - k e n n z e i c h n e t , daß die Kurzschlußwindung (W3) aus einem Metallkörper (10) besteht, auf dem die Windungen (20, 21) der Meßwicklung (W2) aufgewickelt sind.1.Current converter for alternating current measurements in the low-voltage range, with a primary winding for integration into a circuit and two secondary windings coupled with transformers, of which one winding is a short-circuit turn, and of which the other winding has a predetermined number of turns as a measuring winding and can be connected to an evaluation electronics is characterized in that the short circuit winding (W3) consists of a metal body (10) on which the windings (20, 21) of the measuring winding (W2) are wound.
2. Stromwandler nach Anspruch 1, d a d u r c h g e - k e n n z e i c h n e t , daß der Metallkörper der Kurzschlußwindung (W3) ein Ring (10) aus massivem Kupfer-Material ist.2. Current transformer according to claim 1, so that the metal body of the short-circuit winding (W3) is a ring (10) made of solid copper material.
3. Stromwandler nach Anspruch 2, d a d u r c h g e - k e n n z e i c h n e t , daß auf dem Ring (10) ein- oder beidseitig Ringscheiben zur Bereichsanpassung aufbringbar sind.3. Current transformer according to claim 2, d a d u r c h g e - k e n n z e i c h n e t that ring disks can be applied to the ring (10) on one or both sides for area adjustment.
4. Stromwandler nach Anspruch 1, d a d u r c h g e - k e n n z e i c h n e t , daß der Metallkörper der Kurzschlußwindung (W3) im Schnitt als Hohlprofil (10) zur Aufnahme der Meßwicklung (W2) ausgebildet ist.4. Current transformer according to claim 1, d a d u r c h g e - k e n n z e i c h n e t that the metal body of the short-circuit winding (W3) is designed in section as a hollow profile (10) for receiving the measuring winding (W2).
5. Stromwandler nach Anspruch 3, d a d u r c h g e - k e n n z e i c h n e t , daß der Metallkörper der Kurzschlußwindung (W3) im Schnitt als Rechteck-U-Profil (10, 11) ausgebildet ist.5. Current transformer according to claim 3, d a d u r c h g e - k e n n z e i c h n e t that the metal body of the short-circuit winding (W3) is formed on average as a rectangular U-profile (10, 11).
6. Stromwandler nach einem der vorhergehenden Ansprüche, d a du r c h g e k e n n z e i c h n e t , daß die Windungen der Meßwicklung (W2) aus lackisoliertem Kupferdraht (21) bestehen. 6. Current transformer according to one of the preceding claims, since you rchgek characterized that the windings of the measuring winding (W2) consist of enamelled copper wire (21).
7. Stromwandler nach Anspruch 5, d a d u r c h g e k e n n z e i c h n e t , daß der lackisolierte Kupferdraht (21) ein kompaktes Wicklungspaket (20) bildet.7. Current transformer according to claim 5, d a d u r c h g e k e n n z e i c h n e t that the enamel-insulated copper wire (21) forms a compact winding package (20).
8. Stromwandler nach einem der vorhergehenden Ansprüche, d a d u r c h g e k e n n z e i c h n e t , daß durch den Kurzschlußring (10) mehrere Windungen der Primärwicklung (Wl) führbar sind. 8. Current transformer according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that a plurality of turns of the primary winding (Wl) are feasible through the short-circuit ring (10).
PCT/DE1998/001295 1997-05-15 1998-05-08 Current transformer for alternating current measurements in the low voltage range WO1998052054A1 (en)

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DE29708694U DE29708694U1 (en) 1997-05-15 1997-05-15 Current transformers for AC measurements in the low voltage range
DE29708694.4 1997-05-15

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DE102005007971B4 (en) * 2004-02-27 2008-01-31 Magnetec Gmbh Current transformer with compensation winding

Citations (3)

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GB2154806A (en) * 1984-02-15 1985-09-11 Crest Energy Scan Ltd Clip-on current measuring device
WO1993001502A1 (en) * 1991-07-01 1993-01-21 Abb Energi As Arrangement in a current detection circuit
DE19533002A1 (en) * 1995-09-07 1997-03-13 Ludger Wilken High-frequency voltage and current measurement device for conductor

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DE2100529A1 (en) * 1971-01-07 1972-07-20 Kiepe Bahn Elektrik Gmbh Current measuring element equipped with magnetic field-dependent elements such as field plates, Hall generators, magnetic diodes and the like
CH537085A (en) * 1972-04-10 1973-05-15 Sprecher & Schuh Ag Current transducer for obtaining a voltage proportional to the current to be measured
DD214458A1 (en) * 1983-03-31 1984-10-10 Inst Prueffeld Elekt ARRANGEMENT OF SECONDARY DEVELOPMENTS FOR INDUCTIVE MEASURING ARRANGEMENTS FOR ELECTRICAL STROEMES
JPS6060562A (en) * 1983-09-13 1985-04-08 Mitsubishi Electric Corp Current detecting circuit
JPS62173707A (en) * 1986-01-27 1987-07-30 Mitsubishi Electric Corp Current detector for circuit breaker

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Publication number Priority date Publication date Assignee Title
GB2154806A (en) * 1984-02-15 1985-09-11 Crest Energy Scan Ltd Clip-on current measuring device
WO1993001502A1 (en) * 1991-07-01 1993-01-21 Abb Energi As Arrangement in a current detection circuit
DE19533002A1 (en) * 1995-09-07 1997-03-13 Ludger Wilken High-frequency voltage and current measurement device for conductor

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