Split Core Current Transformer with Integrated Bobbin
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Solution Overview
Problem
Existing devices for monitoring the operating state of electrical loads with limited current draws are cumbersome due to their size and cost, particularly when retrofitting existing circuits, and often require additional wiring and complex circuitry, making remote monitoring impractical and expensive.
Innovation Solution
A compact status indicator with a split core current transformer and integral bobbin wound coil, allowing for easy installation without disconnecting the power cable, and integrating the transformer core and current switch to reduce size and cost, while using a resonant circuit with a diode clamp and voltage multiplier to detect low current levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a solid core current transformer is used, then the current sensing accuracy is improved, but the installation complexity increases because the power cable must be disconnected and passed through the core aperture
Solution Approach 1:
The current transformer core is divided into two separable C-shaped segments that can be opened and closed around the power cable. This segmentation allows the cable to remain connected during installation while still achieving accurate current sensing when the segments are assembled together.
2Ease of operation
If a split core current transformer is used, then the installation ease is improved, but the device size increases making it difficult to locate in small electrical enclosures
Solution Approach 1:
The bobbin and coil assembly is integrated directly with one of the C-shaped core segments, eliminating the need for separate mounting structures. This merging reduces the overall device volume while maintaining the split core installation advantage.
Solution Approach 2:
The coil is wound around a bobbin that is itself mounted on the core segment, creating a nested structure. This nesting allows compact packaging of multiple components within a minimal volume, enabling installation in small electrical enclosures.
3Reliability
If additional wiring and relays are used to signal switch state, then the monitoring reliability is improved, but the device complexity and cost increase
Solution Approach 1:
The current transformer serves multiple functions: it senses current for load monitoring and simultaneously provides signaling capability for remote monitoring applications. This multi-functionality eliminates the need for separate relays and additional wiring while maintaining monitoring reliability.
4Measurement precision
If a resonant circuit with voltage multiplier is used, then the current detection threshold is reduced, but the device complexity increases
Solution Approach 1:
The resonant circuit components (capacitor and inductor) are integrated with the transformer structure, and the voltage multiplier is combined with the output terminals. This merging reduces the number of discrete components while achieving low current detection capability.
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
Enables efficient and cost-effective monitoring of electrical loads with currents as low as 0.10 amps, facilitating remote monitoring without the need for additional wiring, and allowing for installation in small enclosures with reduced size and complexity.
Implementation Method 1
Fluctuating current in the power cable produces a changing electromagnetic field around the cable which, in turn, induces a magnetic flux in the core of the current transformer
Implementation Method 2
a capacitor that is selected to cause the circuit to resonate at the expected frequency of the alternating current induced in the secondary winding, typically 50-60 Hz
Data Source
AI summary
The size of a status indicator for monitoring a current in a power cable is reduced by integrating a bobbin for the secondary winding with a current transformer core and integrating a circuit board including output terminals with a current transformer assembly.