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
  • H01F38/30—Constructions
• • 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
• • 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
  • H01F38/30—Constructions
  • H01F2038/305—Constructions with toroidal magnetic core

Definitions

• the present invention relates to a current transformer for low voltage residual current circuit breakers.
• TA current or amperometric transformers
• an amperometric or current transformer comprises a magnetic core and a primary and secondary winding structure operatively associated with the magnetic core.
• the primary winding structure is formed by one or more primary conductors electrically connectable with the terminals or electric contacts of the residual current circuit breaker, in turn connected to the line and/or neutral conductors of an electric line.
• the secondary winding structure is formed by one or more secondary conductors passing through the magnetic core and connectable, for example, with an electronic control device. Operative installation of an amperometric transformer in a residual current circuit breaker often requires the execution of particular shaping operations of the primary conductors, which must often be carried out manually with a possible significant increase in the overall dimensions and production and installation costs of the circuit breaker.
• the main task of the present invention is to provide a current transformer for low voltage residual current circuit breakers that enables the disadvantages described above to be overcome.
• Another object of the present invention is to provide a current transformer that has a particularly simple and sturdy structure.
• a further object of the present invention is to provide a current transformer that is easily installable in a residual current circuit breaker, by means of operations that can be carried out automatically.
• Yet another object of the present invention is to provide a current transformer that is easy and inexpensive to produce at industrial level.
• FIG. 1 schematically illustrate an embodiment of the current transformer according to the present invention
• FIG. 3-5 schematically illustrate a further embodiment of the current transformer according to the present invention
• FIG. 6-7 schematically illustrate a further embodiment of the current transformer according to the present invention
• FIG. 8 schematically illustrates another embodiment of the current transformer according to the present invention.
• FIG. 9 schematically illustrates an example of installation in a residual current circuit breaker of the current transformer according to the present invention, in the embodiment of Figs. 3-5.
• the present invention relates to a current transformer 1 for low voltage residual current circuit breakers.
• the current transformer 1 comprises a first magnetic core 2 having a substantially toroidal structure.
• the magnetic core 2 comprises a first shaped cavity 21 passing through the thickness of the same core.
• the current transformer 1 can comprise a second magnetic core 8 having a substantially toroidal structure.
• the second magnetic core 8, where present, comprises a second shaped cavity 81 passing through the thickness of the same core.
• the magnetic cores 2 and 8 can be disposed side by side (Fig. 7) or separated by a spacer element.
• the current transformer 1 comprises primary winding means comprising one or more primary conductors 31, 32, 33, 34 passing through the magnetic core 2, in particular through the shaped cavity 21.
• the primary conductors 31, 32, 33, 34 also pass through the second magnetic core 8, in particular through the shaped cavity 81.
• each of the primary conductors 31, 32, 33, 34 is arranged so as to pass through the magnetic core 2 only once (thus forming a single turn linked with the magnetic core 2).
• each of the primary conductors 31, 32, 33, 34 is arranged so as to pass through the second magnetic core 8 only once.
• the current transformer 1 comprises secondary winding means comprising one or more first secondary conductors 41 passing through the magnetic core 2, in particular through the shaped cavity 21.
• each of the secondary conductors 41 is arranged so as to pass through the magnetic core 2 several times, thus forming a plurality of turns wound around the magnetic core 2.
• the secondary winding means comprise one or more second secondary conductors 42 passing through the second magnetic core 8, in particular through the shaped cavity 81.
• each of the secondary conductors 42 is arranged so as to pass through the second magnetic core 8 several times.
• the current transformer 1 is arranged so that the primary conductors 31, 32, 33, 34 are electrically connectable with one or more corresponding further conductors 151, 152, 153, 154, 161, 162, 163, 164, for example the terminals or the electric contacts of the residual current circuit breaker in which the transformer is mounted (Figs. 8-9).
• the current transformer 1 comprises first and second electric contacts for connection of the primary conductors 31, 32, 34, 34 to the further conductors 151, 152, 153, 154, 161, 162, 163, 164.
• the current to be detected or measured can circulate along the primary conductors 31, 32, 33, 34.
• the primary conductors 31, 32, 33, 34 are formed by shaped conductive bars.
• the conductive bars 31, 32, 33, 34 pass through the shaped cavity 21 of the magnetic core 2.
• the conductive bars 31, 32, 33, 34 also pass through the shaped cavity 81 of the second magnetic core 8.
• Each of the shaped bars 31 , 32, 33, 34 is advantageously provided with a first shaped end 311, 321, 331, 341 and with a second shaped end 312, 322, 332, 342.
• the conductive bars 31, 32, 33, 34 are advantageously sized (in particular with regard to their diameter or thickness) as a function of the circulating rated current.
• the conductive bars 31, 32, 33, 34 extend rectilinearly but they could have more complex configurations, according to needs.
• the current transformer 1 comprises a first printed circuit 5 that comprises one or more first conductive pads 51, 52, 53, 54.
• the conductive pads 51, 52, 53, 54 are arranged so as to form the aforesaid first electric contacts of the current transformer 1. For this purpose, they are advantageously arranged so as to be electrically isolated from one another.
• the conductive pads 51, 52, 53, 54 can advantageously be produced with known processing techniques and can be positioned at one or more faces of the printed circuit 5 as a function of the type of processing chosen to produce the same printed circuit.
• the conductive pads 51, 52, 53, 54 are arranged at the face of the printed circuit 5 facing the conductive bars 31, 32, 33, 34.
• the conductive pads 51, 52, 53, 54 are configured so as to have a relatively extensive area with respect to the mounting area of the face on which they are positioned, advantageously an area greater than or equal to 90% of the available mounting area.
• the printed circuit 5 is operatively connected (electrically and mechanically) to the conductive bars 31, 32, 33, 34, at the conductive pads 51, 52, 53, 54.
• each of the conductive bars 31, 32, 33, 34 has the respective first shaped end 311, 321, 331, 341 fixed to the printed circuit 5 at a respective conductive pad 51, 52, 53, 54. Coupling between the end 311, 321, 331, 341 of each conductive bar 31, 32, 33, 34 and the corresponding conductive pad 51, 52, 53, 54 is produced so that each of the conductive bars 31, 32, 33, 34 is mechanically supported by the printed circuit 5 and is electrically connected to the respective conductive pad 51, 52, 53, 54.
• the printed circuit 5 is arranged perpendicularly with respect to the conductive bars 31, 32, 33, 34, as illustrated in the aforesaid figures.
• the operative connection between the conductive bars 31, 32, 33, 34 and the conductive pads 51, 52, 53, 54 can be produced by welding or brazing.
• the printed circuit 5 comprises one or more first connection holes 55, 56, 57, 58, each of the which is positioned at a respective conductive pad 51, 52, 53, 54.
• the shaped end 311, 321, 331, 341 of each of the conductive bars 31, 32, 33, 34 is inserted with pressure (coupling of "press-fit” type) in a respective connection hole 55, 56, 57, 58 of the printed circuit 5.
• the conductive bars 31, 32, 33, 34 are mechanically coupled with the printed circuit 5 (which acts as mechanical support for the same) and are electrically connected with the respective conductive pads 51, 52, 53, 54, so as to enable the circulation of current between bars and conductive pads.
• each of the conductive bars 31, 32, 33, 34 is advantageously shaped in the form of a pin and is suitable sized to ensure reliable mechanical and electrical coupling with the edges of the respective connection hole 55, 56, 57, 58 in which it is inserted.
• the operative coupling between the conductive bars 31, 32, 33, 34 and the printed circuit 5 do not require welding or brazing operations.
• the shaped ends 312, 322, 332, 342 of the conductive bars 31, 32, 33, 34 are connectable with the aforesaid second electric contacts of the current transformer 1 by means of electric connections of known type.
• the current transformer 1 comprises a second printed circuit 6.
• the printed circuit 6 comprises one or more second conductive pads 61, 62, 63, 64.
• the conductive pads 61, 62, 63, 64 are arranged so as to form the aforesaid second electric contacts of the current transformer 1.
• the conductive pads 61, 62, 63, 64 can advantageously be produced with known processing techniques and positioned at one or more faces of the printed circuit 6 as a function of the type of processing chosen.
• the conductive pads 61, 62, 63, 64 are arranged at the face of the printed circuit 6 facing the conductive bars 31, 32, 33, 34 of the transformer 1.
• the conductive pads 61, 62, 63, 64 are configured so as to have a relatively extensive area with respect to the mounting area of the face of the printed circuit 6 on which they are positioned, advantageously an area greater than or equal to 90% of the available mounting area.
• the printed circuit 6 is operatively connected (electrically and mechanically) to the conductive bars 31, 32, 33, 34, at the conductive pads 61, 62, 63, 64.
• each of the conductive bars 31, 32, 33, 34 has the respective second shaped end 312, 322, 332, 342 fixed to the printed circuit 6 at a respective conductive pad 61, 62, 63, 64. Coupling between the end 312, 322, 332, 342 of the conductive bars 31, 32, 33, 34 is produced so that each of the conductive bars 31, 32, 33, 34 is mechanically supported by the printed circuit 6 and is electrically connected to the respective conductive pad 61, 62, 63, 64.
• the printed circuit 6 is arranged perpendicularly with respect to the conductive bars 31, 32, 33, 34, as illustrated in Figs. 3-7.
• the operative connection between the conductive bars 31, 32, 33, 34 and the conductive pads 61, 62, 63, 64 can be produced by welding or brazing.
• the printed circuit 6 comprises one or more second connection holes 65, 66, 67, 68, each of which is positioned at a respective conductive pad 61, 62, 63, 64.
• the shaped end 312, 322, 332, 342 of each of the conductive bars 31, 32, 33, 34 is inserted with pressure in a respective connection hole 65, 66, 67, 68 of the printed circuit 6.
• the end 312, 322, 332, 342 of each of the conductive bars 31, 32, 33, 34 is advantageously shaped in the form of a pin and appropriately sized to ensure efficient mechanical and electrical coupling with the edges of the respective connection hole 65, 66, 67, 68 in which it is inserted.
• the current transformer 1 comprises a first partition structure 7 for the conductive bars 31, 32, 33, 34.
• the partition structure 7 is advantageously adapted to act as spacer for the aforesaid conductive bars so as to ensure correct positioning and mutual electric isolation thereof.
• the partition structure 7 is housed in the shaped cavity 21 of the magnetic core 2 so as to reduce the overall dimensions of the current transformer 1.
• the partition structure 7 comprises a plurality of first insulating walls 71 arranged (for example with a cross-shaped configuration) so as to define, two by two, one or more first housings for the conductive bars 31, 32, 33, 34.
• the current transformer 1 preferably comprises a second partition structure 9 for the conductive bars 31, 32, 33, 34.
• the partition structure 9 is housed in the shaped cavity 81 of the second magnetic core 8.
• the partition structure 9 comprises a plurality of first insulating walls 91 arranged (for example with cross-shaped configuration) so as to define, two by two, one or more second housings for the conductive bars 31, 32, 33, 34.
• the current transformer 1 is operatively connected to electronic means 200, for example the control unit of the circuit breaker in which it is mounted.
• the electronic means 200 are electrically connected to the secondary winding means of the current transformer 1, in particular to the first secondary conductors 41 and, where present, to the second secondary conductors 42.
• the electronic means 200 (for example comprising a microprocessor unit) are adapted to receive and process (current) detection or measurement signals coming from the secondary winding means 4.
• the current transformer 1 comprises third electric contacts for connection of the secondary conductors 41 and/or 42 with the aforesaid electronic means.
• the printed circuit 5 and/or the printed circuit 6 comprise at least one mounting space for housing the electronic means 200.
• the printed circuit 5 and/or the printed circuit 6 comprise one or more third pads 201 arranged so as to form the aforesaid third electric contacts of the current transformer.
• the electronic means 200 and the related conductive pads 201 are positioned at one or more faces of the printed circuit 5 and/or of the printed circuit 6.
• the electronic means 200 are operatively positioned at a mounting space 202 of the printed circuit 5.
• they could be operatively positioned only at the printed circuit 6 or at both the printed circuits 5, 6.
• An important aspect of the present invention relates to a residual current circuit breaker 900 that comprises the current transformer 1.
• the residual current circuit breaker 900 comprises the current transformer 1 in the embodiment of Figs. 3-5.
• the circuit breaker 900 comprises the input terminals 181, 182, 183, 184 and the output terminals 161, 162, 163, 164 connectable to one or more conductors (line and/or neutral) of an electric line (not illustrated).
• the circuit breaker 900 also comprises the moving contacts 151, 152, 153, 154 and the fixed contacts 171, 172, 173, 174 mutually couplable/decouplable.
• the current transformer 1 is installed so that the conductive bars 31, 32, 33, 34 are electrically connected to the output terminals 161, 162, 163, 164 of the circuit breaker and to the moving contacts 151, 152, 153, 154.
• the conductive pads 51, 52, 53, 54 are thus electrically connected with the moving contacts 151, 152, 153, 154 while the conductive pads 61, 62, 63, 64 are electrically connected with the output terminals 161, 162, 163, 164.
• the conductive bars 31, 32, 33, 34 of the current transformer 1 thus ensure electrical continuity between the output terminals and the moving contacts of the circuit breaker 900.
• the current transformer 1 is capable of detecting circulation of residual fault currents along the conductive bars 31, 32, 33, 34 and, therefore, the presence of earth leakage currents in the electric line connected to the input and output terminals of the circuit breaker 900.
• the conductive pads 51, 52, 53, 54, 61, 62, 63, 64 are already electrically connected to the conductive bars 31, 32, 33, 34 and in a predefined position with respect to this latter.
• the current transformer 1 has a sturdy and compact structure, easily connectable with the terminals or electric contacts of the circuit breaker.
• Installation of the current transformer 1 in a switch can be carried out by means of operations that can be easily automated at industrial level.
• the current transformer 1 is easy to produce at industrial level at competitive costs with amperometric transformers for low voltage residual current circuit breakers of know type.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Transformers For Measuring Instruments (AREA)
• Electronic Switches (AREA)

Priority Applications (2)

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Publications (1)

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Family Applications (1)

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Citations (2)

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• 2013
  • 2013-10-17 IT IT001736A patent/ITMI20131736A1/it unknown
• 2014
  • 2014-10-14 WO PCT/EP2014/071978 patent/WO2015055628A1/en active Application Filing
  • 2014-10-14 EP EP14795967.0A patent/EP3058576B1/de not_active Not-in-force
  • 2014-10-14 CN CN201480057110.XA patent/CN105706194A/zh active Pending

Patent Citations (2)

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