Combined nested low voltage winding current transformer

Abstract

The combined nested low-voltage winding current transformer comprises a shell, at least two ring-shaped cores are arranged in the shell, the at least two ring-shaped cores comprise an inner core and an outer core, a first secondary winding is wound on the inner core, a second secondary winding is wound on the outer core, the number of turns of the first secondary winding is greater than the number of turns of the second secondary winding, the inner diameter of the outer core is greater than the outer diameter of the inner core, an insulating layer is arranged on the outer peripheral surface of the inner core, the inner core is nested in the inner ring of the outer core, and the insulating layer is located between the first secondary winding and the second secondary winding. Through the setting of the nested double winding, the current transformer has the variable ratio characteristic and can realize multi-winding measurement, meets different needs of measurement and protection devices, is especially suitable for compact occasions such as switch cabinets, and has the effect of significantly saving installation space.

Description

Technical Field

[0001] This utility model relates to power equipment, and in particular to current transformers. Background Technology

[0002] A current transformer (CT) is a key device used in power systems for measurement and protection. It primarily converts high currents to low currents proportionally for measurement or control. CTs can be categorized into measurement CTs that prioritize accuracy and typically require no high voltage when the secondary side is open, and protection CTs that prioritize saturation resistance and must maintain output under fault current conditions.

[0003] However, in situations where space is limited, such as switchgear, multiple winding measurements are required to monitor dual or segmented busbar systems, and high reliability redundancy is needed. In such cases, multiple independent current transformers are required. Therefore, a current transformer with transformation ratio characteristics that can achieve multi-winding measurements while also saving space is needed. Utility Model Content

[0004] The purpose of this invention is to provide a combined nested low-voltage winding current transformer to solve the problems existing in the prior art.

[0005] The above-mentioned technical objective of this utility model is achieved through the following technical solution:

[0006] A combined nested low-voltage winding current transformer includes a housing, within which at least two annular iron cores are disposed;

[0007] At least two annular cores, including an inner core and an outer core;

[0008] The inner iron core is wound with first and second windings;

[0009] The outer iron core is wound with a second and secondary winding;

[0010] The number of turns in the first secondary winding is greater than the number of turns in the second secondary winding;

[0011] The inner diameter of the outer iron core is larger than the outer diameter of the inner iron core, and an insulating layer is provided on the outer circumferential surface of the inner iron core;

[0012] The inner iron core is nested within the inner ring of the outer iron core;

[0013] The insulation layer is located between the first secondary winding and the second secondary winding.

[0014] By adopting the above technical solution, different turns ratios are achieved in the first and second secondary windings, resulting in different current transformation ratios. By selecting a suitable low-voltage winding output, the current signal requirements of different measurement or protection devices can be met. The larger number of turns in the inner winding provides higher magnetic field coupling efficiency, reduces magnetic leakage, improves transformation ratio accuracy, and enhances resistance to external interference. Heat in the inner layer is quickly conducted through the iron core, and the larger number of turns results in more even temperature rise and better heat dissipation. At the same time, the insulation layer between the first and second secondary windings separates the two coils, maintaining sufficient insulation distance. In addition, insulation materials such as insulating varnish and insulating paper are used to isolate the windings from each other and from the iron core, effectively preventing faults such as leakage and short circuits. Furthermore, the nested arrangement of the first and second secondary windings significantly reduces the overall size and space occupied by the equipment compared to multiple independent current transformers, offering a clear advantage in space-constrained applications such as switch cabinets.

[0015] In a further embodiment, the first secondary winding and the second secondary winding are spaced 0.5 mm to 1 mm apart.

[0016] By adopting the above technical solution, the design of this spacing distance optimizes space utilization while ensuring insulation safety. The spacing of 0.5mm to 1mm can effectively prevent partial discharge caused by electric field concentration between windings, and avoid volume redundancy caused by excessive spacing. This distance is determined by the dielectric strength calculation of the insulating material to ensure that breakdown does not occur under rated voltage. For high-frequency interference, this distance combined with the insulation layer can form a certain distributed capacitance, which helps to suppress the coupling of common-mode noise.

[0017] In a further embodiment, the first and second windings are also wound with nanocrystalline ribbons for suppressing high-frequency interference, and the nanocrystalline ribbons are bonded and fixed to the outer layer of the first and second windings.

[0018] By adopting the above technical solution, the high permeability of the nanocrystalline ribbon can effectively absorb high-frequency electromagnetic noise and reduce its interference with the winding signal. Its bonding and fixing method with the outer layer of the winding avoids the friction loss caused by the loosening of the traditional shielding layer, while ensuring that the magnetic field coupling efficiency is not affected. The thin-layer structure of the nanocrystalline ribbon will not significantly increase the winding volume, and its temperature resistance is compatible with the winding insulation material, further improving the stability of the equipment in complex electromagnetic environments.

[0019] In a further embodiment, the insulating layer is made of polyurethane.

[0020] By adopting the above technical solutions, polyurethane materials have excellent dielectric properties and mechanical toughness. Their high breakdown voltage characteristics can meet the insulation requirements between windings, while their elastic properties can buffer vibration stress during operation and prevent the insulation layer from cracking. Polyurethane also has the characteristics of resistance to damp heat aging and can maintain insulation reliability after long-term operation.

[0021] In a further embodiment, the insulating layer includes a polyurethane layer for insulation and a silicone layer for thermal conductivity;

[0022] One side of the silicone layer is bonded and fixed to the polyurethane layer;

[0023] The other side of the silicone layer is in contact with the inner circumferential surface of the second winding.

[0024] By adopting the above technical solution, the composite insulation layer achieves synergistic optimization of insulation and heat dissipation through functional layering. The polyurethane layer provides primary insulation protection, while the high thermal conductivity of the silicone layer can quickly dissipate heat from the inner winding, avoiding excessive local temperature rise. The bonding and fixing of the two layers uses a chemically compatible adhesive to ensure no risk of delamination at the interface. This structure is particularly suitable for high-load conditions, and the optimized design of the thermal conduction path significantly improves the long-term thermal stability of the winding.

[0025] In a further embodiment, the outer shell is provided with a permalloy shielding layer for suppressing external magnetic field interference.

[0026] By adopting the above technical solution, the high permeability of permalloy can effectively shield external alternating magnetic fields, preventing them from interfering with the internal magnetic circuit of the transformer. The integrated design of the shielding layer and the shell avoids the occupation of additional installation space. At the same time, its low coercivity reduces hysteresis loss. The shielding layer has a particularly significant effect on suppressing low-frequency magnetic fields (especially power frequency interference), further improving the accuracy of the output signal.

[0027] In summary, this utility model has the following beneficial effects:

[0028] 1. By setting up nested double windings, multiple current ratio outputs can be achieved to meet the different needs of measurement and protection devices. The inner winding adopts a high number of turns structure, which improves the magnetic field coupling efficiency, reduces magnetic leakage, and ensures the accuracy of the ratio. The outer winding takes into account the anti-saturation capability through reasonable turn configuration, which is especially suitable for compact occasions such as switch cabinets. The setting of the insulation layer ensures electrical isolation between windings, while optimizing the heat dissipation path and making the temperature rise distribution more uniform, which improves the long-term reliability of the equipment. The layout of coaxial nested double windings also significantly saves installation space.

[0029] 2. By using composite insulation layers, insulation strength and heat dissipation performance can be balanced. The polyurethane layer provides high dielectric strength and mechanical toughness to prevent insulation aging and cracking, while the silicone layer enhances thermal conductivity to avoid localized overheating. The winding spacing of 0.5mm to 1mm not only meets insulation safety requirements but also suppresses high-frequency interference through distributed capacitance. This layered insulation structure improves thermal stability while ensuring electrical performance, making it more suitable for high-load or frequent start-stop conditions.

[0030] 3. By combining nanocrystalline ribbons with permalloy shielding layers, internal and external electromagnetic interference can be effectively suppressed. The nanocrystalline ribbons are wound around the inner winding to absorb high-frequency noise, while the permalloy outer shielding layer blocks external low-frequency magnetic fields. The two work together to significantly improve the anti-interference capability of the output signal, ensuring measurement accuracy and the reliability of protection actions. In addition, the integrated design of the shielding layer and the outer shell avoids an increase in volume, achieving a balance between compactness and electromagnetic compatibility. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the outer shell structure in the combined nested low-voltage winding current transformer of this utility model.

[0032] Figure 2 This is a schematic diagram illustrating the internal structure of the housing in the combined nested low-voltage winding current transformer of this utility model.

[0033] In the diagram, 1 is the outer casing; 2 is the first and second windings; 3 is the second and second windings; and 4 is the insulation layer. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings.

[0035] Identical parts are indicated by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to the attached figures. Figure 1 In this specification, the terms "bottom surface" and "top surface," "inner" and "outer" refer to the direction toward or away from the geometry of a specific component. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this specification, "a plurality of" means two or more, unless otherwise explicitly and specifically defined by the direction of the center.

[0036] like Figures 1-2As shown, a combined nested low-voltage winding current transformer includes a housing 1, inside which at least two annular iron cores are arranged. The at least two annular iron cores include an inner iron core and an outer iron core. A first secondary winding 2 is wound on the inner iron core, and a second secondary winding 3 is wound on the outer iron core. The number of turns of the first secondary winding 2 is greater than the number of turns of the second secondary winding 3. The inner diameter of the outer iron core is greater than the outer diameter of the inner iron core. An insulating layer 4 is provided on the outer circumferential surface of the inner iron core. The inner iron core is nested in the inner ring of the outer iron core, and the insulating layer 4 is located between the first secondary winding 2 and the second secondary winding 3.

[0037] By adopting the above technical solution, the different turns ratios of the first and second secondary windings 2 and 3 achieve different current transformation ratios. By selecting a suitable low-voltage winding output, the current signal requirements of different measurement or protection devices can be met. The larger number of turns in the inner winding provides higher magnetic field coupling efficiency, reduces magnetic leakage, improves transformation ratio accuracy, and has stronger resistance to external interference. The heat in the inner layer is quickly conducted through the iron core, and the larger number of turns results in a more even temperature rise and better heat dissipation. At the same time, the insulation layer 4 between the first and second secondary windings 2 and 3 also separates the two coils, maintaining sufficient insulation distance. In addition, insulating materials such as insulating varnish and insulating paper are used to isolate the windings from each other and from the iron core, effectively preventing faults such as leakage and short circuit. Moreover, the nested arrangement of the first and second secondary windings 2 and 3 significantly reduces the overall size and space occupied by the equipment compared to multiple independent current transformers, which has obvious advantages in space-constrained occasions such as switch cabinets.

[0038] In a further embodiment, the first secondary winding 2 and the second secondary winding 3 are spaced 0.5mm to 1mm apart.

[0039] By adopting the above technical solution, the design of this spacing distance optimizes space utilization while ensuring insulation safety. The spacing of 0.5mm to 1mm can effectively prevent partial discharge caused by electric field concentration between windings, and avoid volume redundancy caused by excessive spacing. This distance is determined by the dielectric strength calculation of the insulating material to ensure that no breakdown occurs under rated voltage. For high-frequency interference, this distance combined with the insulating layer 4 can form a certain distributed capacitance, which helps to suppress the coupling of common-mode noise.

[0040] In a further embodiment, the first and second windings 2 are also wound with nanocrystalline ribbons for suppressing high-frequency interference, and the nanocrystalline ribbons are bonded and fixed to the outer layer of the first and second windings 2.

[0041] By adopting the above technical solution, the high permeability of the nanocrystalline ribbon can effectively absorb high-frequency electromagnetic noise and reduce its interference with the winding signal. Its bonding and fixing method with the outer layer of the winding avoids the friction loss caused by the loosening of the traditional shielding layer, while ensuring that the magnetic field coupling efficiency is not affected. The thin-layer structure of the nanocrystalline ribbon will not significantly increase the winding volume, and its temperature resistance is compatible with the winding insulation material, further improving the stability of the equipment in complex electromagnetic environments.

[0042] In a further embodiment, the insulating layer 4 is made of polyurethane.

[0043] By adopting the above technical solutions, polyurethane materials have excellent dielectric properties and mechanical toughness. Their high breakdown voltage characteristics can meet the insulation requirements between windings, while their elastic properties can buffer vibration stress during operation and prevent the insulation layer 4 from cracking. Polyurethane also has the characteristics of resistance to damp heat aging and can maintain insulation reliability after long-term operation.

[0044] In a further embodiment, the insulating layer 4 includes a polyurethane layer for insulation and a silicone layer for thermal conductivity. One side of the silicone layer is bonded to the polyurethane layer, and the other side of the silicone layer is in contact with the inner circumferential surface of the second secondary winding 3.

[0045] By adopting the above technical solution, the composite insulation layer 4 achieves synergistic optimization of insulation and heat dissipation through functional layering. The polyurethane layer provides primary insulation protection, while the high thermal conductivity of the silicone layer can quickly dissipate heat from the inner winding, avoiding excessive local temperature rise. The bonding and fixing of the two uses a chemically compatible adhesive to ensure no risk of delamination at the interface. This structure is particularly suitable for high-load conditions, and the optimized design of the thermal conduction path significantly improves the long-term thermal stability of the winding.

[0046] In a further embodiment, the outer casing 1 is provided with a permalloy shielding layer for suppressing external magnetic field interference.

[0047] By adopting the above technical solution, the high permeability of permalloy can effectively shield external alternating magnetic fields, preventing them from interfering with the internal magnetic circuit of the transformer. The integrated design of the shielding layer and the outer shell 1 avoids the occupation of additional installation space. At the same time, its low coercivity reduces hysteresis loss. The shielding layer has a particularly significant effect on suppressing low-frequency magnetic fields (especially power frequency interference), further improving the accuracy of the output signal.

[0048] In the embodiments disclosed in this utility model, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments disclosed in this utility model according to the specific circumstances.

[0049] This specific embodiment is merely an explanation of the present utility model and is not intended to limit the present utility model. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present utility model, they are protected by patent law.

Claims

1. A combined nested low-voltage winding current transformer, comprising a housing (1), characterized in that: The outer casing (1) is provided with at least two annular iron cores; At least two annular cores, including an inner core and an outer core; The inner iron core is wound with first and second windings (2); The outer iron core is wound with a second secondary winding (3); The number of turns of the first secondary winding (2) is greater than the number of turns of the second secondary winding (3); The inner diameter of the outer core is larger than the outer diameter of the inner core, and an insulating layer (4) is provided on the outer circumferential surface of the inner core; The inner iron core is nested within the inner ring of the outer iron core; The insulation layer (4) is located between the first secondary winding (2) and the second secondary winding (3).

2. The combined nested low-voltage winding current transformer according to claim 1, characterized in that: The first secondary winding (2) and the second secondary winding (3) are spaced 0.5 mm to 1 mm apart.

3. The combined nested low-voltage winding current transformer according to claim 2, characterized in that: The first and second windings (2) are also wound with nanocrystalline ribbons for suppressing high-frequency interference, and the nanocrystalline ribbons are bonded and fixed to the outer layer of the first and second windings (2).

4. The combined nested low-voltage winding current transformer according to claim 1, characterized in that: The insulating layer (4) is made of polyurethane.

5. The combined nested low-voltage winding current transformer according to claim 1, characterized in that: The insulating layer (4) includes a polyurethane layer for insulation and a silicone layer for thermal conductivity; One side of the silicone layer is bonded and fixed to the polyurethane layer; The other side of the silicone layer is in contact with the inner circumferential surface of the second winding (3).

6. The combined nested low-voltage winding current transformer according to claim 1, characterized in that: The outer shell (1) is provided with a permalloy shielding layer for suppressing external magnetic field interference.

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