Integrated Primary Conductor Current Transducer with Overmolded Insulation
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Solution Overview
Problem
Existing current transducers face challenges in achieving compactness, reliability, and robustness, especially under mechanical and thermal stresses, while maintaining accurate and reliable current measurement, particularly when mounted on circuit boards with limited space and requiring high electrical creepage distances.
Innovation Solution
A current transducer design featuring a magnetic core, integrated with a primary conductor and magnetic field detector, is encapsulated within an insulating body with overmolded thermoplastic and thermosetting polymer portions, ensuring precise positioning, insulation, and robust assembly, using a leadframe conductor arrangement with aligned conductors and a magnetic flux concentrator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic core is used to improve measurement accuracy and reliability, then the transducer size and weight increase
Solution Approach 1:
The primary conductor is integrated within the magnetic core structure, with the conductor passing through the central aperture of the core. This nesting approach allows the conductor to be positioned centrally within the magnetic flux path, maximizing measurement accuracy while minimizing the overall transducer footprint and weight.
Solution Approach 2:
The magnetic core serves multiple functions simultaneously: it provides the magnetic flux path for accurate current measurement, acts as a structural support for the sensor assembly, and defines the mechanical mounting interface on the circuit board. This multi-functionality eliminates the need for separate structural components, reducing overall weight.
2Volume of moving object
If the transducer is made compact to reduce size, then the electrical creepage distance between the primary conductor and detector conductors decreases
Solution Approach 1:
The housing is designed with differentiated local properties: the region surrounding the primary conductor incorporates enhanced insulating material or increased creepage distance in critical areas, while other regions of the housing maintain compact dimensions. This localized quality enhancement ensures electrical insulation reliability without compromising overall compactness.
Solution Approach 2:
The design utilizes three-dimensional spatial arrangement to maximize creepage distance in vertical or radial directions while maintaining a compact planar footprint. The primary conductor is positioned centrally through the magnetic core, and detector conductors are arranged in surrounding layers, creating adequate insulation paths in multiple dimensions without increasing the transducer's surface area.
3Manufacturing precision
If the housing is made rigid to maintain positioning under mechanical stress, then the transducer becomes more susceptible to stress-induced failures
Solution Approach 1:
The housing is constructed from composite materials or multi-layer structures that combine rigidity for precise component positioning with flexibility or shock-absorbing properties for mechanical stress resistance. This composite structure maintains the geometric relationships between the magnetic core, primary conductor, and detector while accommodating thermal expansion and mechanical shocks without causing stress-induced failures.
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
The design provides a compact, reliable, and robust current transducer with high electrical tracking resistance, large operating range, and ease of implementation, suitable for mechanical and thermal stress resistance, while maintaining precise current measurement.
Implementation Method 1
a magnetic core (6) comprising a central passage (18) and a magnetic circuit gap (22)
Implementation Method 2
a magnetic field detector (8) positioned in the magnetic circuit gap (22)
Implementation Method 3
an insulating body (10) comprising an inner overmold portion (20) surrounding a central portion (15) of the primary conductor (14)
Data Source
Figure 1a~1d
Figure 2a
Figure 2b
AI summary
Electrical current transducer including an insulating body (10), a magnetic core (6) comprising a central passage (18) and a magnetic circuit gap (22), a magnetic field detector (8) positioned in the magnetic circuit gap, and a sheet metal leadframe conductor arrangement (4) comprising a primary conductor (14) for carrying the current to be measured and secondary conductors (16) for connecting the magnetic field detector to an external circuit, the primary conductor comprising a central portion (15) extending through the central passage of the magnetic core, lateral extension arms (13) extending from opposite ends of the central portion, and connection ends (17) for connection to an external conductor, the secondary conductors comprising a plurality of conductors, each conductor comprising a sensing cell connection pad (21) substantially aligned with the central portion of the primary conductor and a connection end (19) for connection to the external circuit, the insulating body comprising an inner overmold portion (20) surrounding a central portion (15) of the primary conductor and forming a core guide (32) positioning and insulating the magnetic core with respect to the leadframe conductor arrangement. The insulating body further comprises an outer overmold portion (34) molded over the inner overmold portion, the magnetic core, magnetic field sensor, and a central portion of the leadframe conductor arrangement.