Current Transformer with Solid and Gapped Laminations
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Solution Overview
Problem
Existing motor circuit protectors have limited current range capabilities, leading to inadequate protection for both low and high current levels, requiring separate current transformers for power and sensing, which increases size, complexity, and cost.
Innovation Solution
A current transformer system using a combination of solid and gapped laminations to extend the range of sensed currents, with adjustable ratios of solid-to-gapped laminations and varying primary coil turns to achieve a wide operating range, allowing for accurate sensing of both low locked-rotor and high instantaneous short-circuit currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current transformer is designed to sense low fault currents, then it can detect low current levels, but it cannot effectively sense high fault currents
Solution Approach 1:
The current transformer core is segmented into multiple laminations with different gap configurations. Some laminations have gaps optimized for low current sensing, while others have gaps optimized for high current sensing. This segmentation allows the single transformer to handle both low and high fault currents effectively without requiring separate transformers for each range.
Solution Approach 2:
The core uses composite construction with laminations having different magnetic properties. By combining laminations with different gap sizes and magnetic characteristics, the transformer achieves a composite response that covers both low and high current ranges, enabling versatile sensing capability across the entire operating spectrum.
2Measurement precision
If a current transformer is designed to sense high fault currents, then it can detect high current levels, but it cannot effectively sense low fault currents
Solution Approach 1:
The current transformer core is segmented into multiple laminations with different gap configurations. Some laminations have gaps optimized for low current sensing, while others have gaps optimized for high current sensing. This segmentation allows the single transformer to handle both low and high fault currents effectively without requiring separate transformers for each range.
Solution Approach 2:
The core uses composite construction with laminations having different magnetic properties. By combining laminations with different gap sizes and magnetic characteristics, the transformer achieves a composite response that covers both low and high current ranges, enabling versatile sensing capability across the entire operating spectrum.
3Reliability
If separate current transformers are used for power supply and current sensing, then each function can be optimized, but the device size, complexity, and cost increase
Solution Approach 1:
The patent merges the power supply function and current sensing function into a single current transformer device. The core with its multi-lamination structure provides both functions simultaneously, eliminating the need for separate transformers. This consolidation reduces device size, simplifies the overall system, and lowers cost while maintaining the reliability of optimized functional performance.
Solution Approach 2:
The current transformer is designed as a universal device that performs multiple functions: providing power to the trip unit electronics and sensing both low and high fault currents. This multi-functionality is achieved through the specialized core construction with laminations having different gap configurations, allowing a single component to replace what would traditionally require multiple separate components.
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 solution enables a single current transformer to effectively sense a wide range of currents from 10 A to 3000 A, providing comprehensive protection without the need for additional transformers, thus reducing size, complexity, and cost while enhancing accuracy and reliability.
Implementation Method 1
a current transformer that extends the range of a circuit breaker, such as a motor circuit protector, includes both solid and gapped laminations that are staked and stacked together to form a single core
Implementation Method 2
The gapped laminations decrease the amount of remnant flux or saturation in the current transformer compared to solid cores
Data Source
AI summary
In a circuit breaker, a current transformer for fault powering trip unit electronics and sensing low currents and high currents includes a core with solid laminations and gapped laminations to sense a wide range of currents from locked-rotor currents to high, instantaneous short-circuit currents in a single current transformer. The current transformer can also fault power trip unit electronics without requiring an additional current transformer. The operating range of the circuit breaker is significantly enhanced compared to existing breakers that can sense only a limited range of current levels.