Universal Input Circuit for Current Transformer and di/dt Sensor
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Solution Overview
Problem
Current sensing technologies, such as current transformers and Rogowski coils, produce different types of outputs, making it challenging to handle them with a single input system, leading to potential errors and increased complexity in circuit breaker applications.
Innovation Solution
A circuit design that can receive input from either a current transformer or a di/dt sensor, outputting a signal corresponding to the input, with parallel arrangements of current transformer and di/dt sensor input circuits, and optional components like resistors, capacitors, and amplifiers to process and differentiate between the two types of sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple input pairs are provided for different sensor types, then each sensor type can be properly handled, but device complexity increases and user error potential increases
Solution Approach 1:
The patent implements a universal input circuit design that can accept both current transformer outputs and di/dt sensor outputs through a single input pair. The circuit uses automatic detection to identify the sensor type and applies the appropriate processing path, eliminating the need for multiple dedicated input pairs and simplifying the user interface while maintaining full compatibility with different sensor types.
Solution Approach 2:
The patent introduces an intermediary detection and routing circuit that sits between the sensor input and the processing stages. This intermediary automatically identifies whether the input comes from a current transformer or a di/dt sensor and directs the signal through the appropriate processing path, thereby resolving the contradiction between handling multiple sensor types and maintaining simple input configuration.
2Measurement precision
If current transformer is used, then output current is proportional to primary current with constant proportionality, but the device is larger and heavier
Solution Approach 1:
The patent combines both current transformer and di/dt sensor capabilities into a single integrated circuit system. By merging the functionality of both sensor types into one universal input interface with automatic detection and processing, the system allows users to choose the lighter di/dt sensor when appropriate while maintaining the measurement accuracy benefits of current transformers when needed, thus resolving the weight-precision contradiction.
3Weight of moving object
If di/dt sensor is used, then the sensor is smaller and lighter, but the output voltage is small and only maintained for high impedance loads
Solution Approach 1:
The patent implements automatic impedance adaptation in the input circuit that detects the sensor type and adjusts the circuit parameters accordingly. When a di/dt sensor is detected, the circuit automatically configures for high impedance loading to maintain output signal stability. This parameter adaptation resolves the contradiction by ensuring reliable signal output from lightweight di/dt sensors without requiring the user to manually configure impedance settings.
4Adaptability or versatility
If multiple input pairs are provided for different sensor types, then each sensor type can be properly handled, but ease of operation decreases due to connection errors
Solution Approach 1:
The patent implements a self-identifying input system that automatically detects which sensor type is connected and configures the processing circuitry accordingly without user intervention. The automatic detection mechanism eliminates the need for users to manually select or configure input pairs, thereby preventing connection errors while maintaining full compatibility with both current transformer and di/dt sensor types.
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 seamless integration and error-free handling of both current transformer and di/dt sensor outputs, reducing the need for multiple input pairs and minimizing user errors in circuit breaker systems.
Implementation Method 1
a current transformer input circuit connected between the first input and the second input and configured to sense a current and output a signal proportional to the sensed current
Implementation Method 2
a di/dt sensor input circuit connected between the first input and the second input and configured to sense a current and output a voltage proportional to a time rate of change of the sensed current
Data Source
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Figure 5
AI summary
A circuit for receiving the output from one of either a current transformer or a di/dt sensor includes: an input pair having a first input and a second input; a first output; a second output; a current transformer input circuit connected between the first input and the second input; and a di/dt sensor input circuit connected between the first input and the second input. The current transformer input circuit is configured to receive output from a current transformer connected to the input pair and to output a signal representative of the current sensed thereby via the first output. The di/dt sensor input circuit is configured to receive output from a di/dt sensor connected to the input pair and to output a signal representative of the current or time rate of change of the current sensed thereby via the second output.