Residual-Current Transformer Circuit Using Dwell-Time Signal Evaluation
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Solution Overview
Problem
Existing AC/DC-sensitive residual-current measurement technologies require high development effort, high initial costs, and are not suitable for measuring small residual currents at high resolution due to the use of complex ASICs and discrete circuit structures, which are not efficient or economical.
Innovation Solution
An electric circuit arrangement with a driver module and oscillation circuit forming an integral unit, supplied by a shared unipolar voltage, uses a measuring current transformer with a toroid and secondary winding to generate a time-modulated binary measuring signal, evaluated by a microprocessor-based computing unit for flexible and efficient measurement of residual currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an ASIC is used for AC/DC-sensitive residual-current measurement, then measurement precision is improved, but device complexity and initial costs increase
Solution Approach 1:
The patent replaces the ASIC (application-specific integrated circuit) with a microprocessor-based computing unit that executes software programs. This substitution transforms the hardware-intensive measurement system into a software-driven system, maintaining high measurement precision while significantly reducing device complexity and development costs. The microprocessor reads raw measurement data from the current transformer and performs digital signal processing to determine residual current values.
Solution Approach 2:
The patent changes the operational parameters of the oscillation circuit by controlling it to pass through the magnetization curve in an oscillating manner between upper and lower saturation points. This parameter control creates distinct first and second states with different dwell times, enabling precise measurement of residual currents through temporal analysis rather than requiring complex ASIC circuitry.
2Adaptability or versatility
If discrete circuit structures are used, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent implements a universal measurement platform where a single microprocessor-based system can handle multiple measurement tasks and configurations through software programming. The oscillation circuit and evaluation system are designed to be adaptable to different measurement requirements without requiring hardware modifications, thus achieving high versatility while maintaining circuit simplicity.
Solution Approach 2:
The patent replaces complex discrete circuit structures with a microprocessor-controlled system that achieves adaptability through software rather than hardware reconfiguration. This allows the same physical circuit to be adapted to different measurement scenarios by changing the evaluation algorithm, eliminating the need for multiple discrete circuits for different functions.
3Measurement precision
If high-resolution measurement of small residual currents is implemented, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses digital signal processing in the microprocessor to achieve high-resolution measurement of small residual currents. Instead of requiring complex analog circuitry with high precision components, the system uses software-based evaluation of the oscillation signal's dwell times, which can resolve very small current variations through computational algorithms.
Solution Approach 2:
The oscillation circuit operates with feedback control to maintain stable oscillation between saturation points. The system continuously monitors the oscillation signal and uses this feedback to accurately determine dwell times, enabling high-resolution measurement through iterative refinement rather than requiring inherently high-precision hardware 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
Enables efficient and economical measurement of residual currents up to 300 mA with high resolution, reducing circuit complexity and electromagnetic interference, and allowing adaptable measuring parameters through software-based evaluation.
Implementation Method 1
A variable magnetic flux caused within the toroid by this residual current induces a voltage in a secondary winding of the measuring current transformer
Implementation Method 2
the magnetization curve of the transformer core of the measuring current transformer is passed in an oscillating manner by a controlled, secondary-side current flow between an upper and a lower saturation
Data Source
AI summary
An electric circuit arrangement and to a measuring method for the galvanically separate, AC/DC-sensitive residual-current measurement, the measuring method including registering a residual current (Id) by means of a measuring current transformer having a toroid and precisely one secondary winding; supplying power to the secondary winding and generating a time-modulated, binary measuring signal (V) having a corresponding dwell time (Th, T1) in a first state (S1) and a second state (S2) by means of a driver circuit having an oscillation circuit; evaluating the dwell times (Th, T1) by means of a computing unit and outputting a residual-current measured value (Im, I'm) by a data interface, wherein the driver circuit having the oscillation circuit forms an integral structural unit in the form of a driver module, which is supplied with a shared, unipolar operating voltage (Ub) by a power-supply device together with the computing unit.