Zero-Phase Current Transformer Conductor Segmentation for Leakage Detection
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Solution Overview
Problem
Existing earth leakage detection units face challenges in assemblability and miniaturization due to complex conductor processing and large annular core requirements, with issues such as bubble formation and crack development in insulating resin and complicated assembly of bifurcated conductor members.
Innovation Solution
The design features a zero-phase current transformer with a perfectly circular or oval annular core and sectorial or quadrilateral cross-section through conductor portions, along with insulating plate members between conductor joining portions, allowing for easier assembly and miniaturization by eliminating the need for a large inner hole and simplifying conductor processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating resin is used to fill interspaces between conductors, then insulation between phases is maintained, but bubbles and cracks develop causing degradation in insulation
Solution Approach 1:
The patent divides the conductor connection structure into modular units with pre-formed insulating barriers. Instead of filling entire interspaces with insulating resin, the conductors are segmented with insulating plates or coatings at critical junction points, eliminating the need for complex resin filling operations and preventing bubble formation while maintaining phase insulation.
Solution Approach 2:
The patent introduces insulating plates or insulating coatings as intermediary elements between conductors of different phases. These intermediaries provide reliable insulation without requiring large volumes of insulating resin, thereby preventing defects while simplifying the manufacturing process.
2Ease of manufacture
If conductor members are formed in bifurcated shape to interconnect power supply and load side conductors, then connections are established, but processing and forming become complicated and assembly is troublesome
Solution Approach 1:
The patent segments the conductor connection path into separate, simple-shaped conductor members rather than using complex bifurcated conductors. Each conductor member has a straightforward geometry that is easy to process and form, while the segmented arrangement achieves the same connection functionality between power supply and load side conductors.
Solution Approach 2:
The patent resolves the connection complexity by arranging conductor members in different spatial dimensions or planes rather than requiring complex three-dimensional bifurcated shapes. This dimensional reorganization allows simple-shaped conductors to achieve the same interconnection function, greatly simplifying processing and assembly.
3Ease of operation
If inner hole of annular core is enlarged to insert bifurcated conductor members, then conductor insertion is possible, but zero-phase current transformer and earth leakage detection unit become large
Solution Approach 1:
The patent segments the conductor insertion process into separate, linear insertion paths through the annular core. Instead of inserting large bifurcated conductors that require a large inner hole, simple-shaped conductor members are inserted through smaller, separate openings or paths, maintaining a compact transformer design while enabling easy conductor installation.
Solution Approach 2:
The patent inverts the conventional approach by having conductor members insert into the annular core rather than the core accommodating large pre-formed bifurcated conductors. This reversal allows the use of smaller, simpler conductor geometries that fit through smaller openings, thereby reducing the overall device size while maintaining ease of insertion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances assemblability and miniaturization by maintaining effective insulation and reducing the size of the device, while allowing for efficient connection of load and power supply side conductors through the annular core without the need for a large inner hole, and simplifies the processing of conductor members.
Implementation Method 1
a zero-phase current transformer is, as is well known, a device to send currents of all phases through the inner hole of an annular core and, when a so-called secondary current is produced on the annular core, judge that an earth leakage (earth fault) has occurred
Data Source
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Figure 5~7
AI summary
To provide an earth leakage detection unit and an earth leakage breaker that make processing of conductor members easy, enable miniaturization of a device, and, in particular, excel in assemblability. Load side conductors (11T to 11N) and power supply side conductors (12T to 12N) are arranged on the one side and the other side in the axial direction of a zero-phase current transformer (8), respectively, so that through conductor portions (14S, 14N) and through conductor portions (13N, 13R) each of which are continuously fixed penetrate an annular core (9) from the one side and the other side in the axial direction of the zero-phase current transformer (8), respectively. With this configuration, the through conductor portions (13T, 13R, 14S, 14N) are jointed to joining portions (16T, 16R, 15S, 15N), and the power supply side conductors (12T to 12N) and the load side conductors (11T to 11N) are connected for each phase. Insulating coating portions (18S, 18N, 17R) are formed at least on the outsides of portions of the through conductor portions continuously fixed to the load side conductors and the power supply side conductor.