Current Sensor Resampling for Magnetic Saturation Detection
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Solution Overview
Problem
Current sensor devices erroneously detect large-amplitude alternating current components as direct current due to magnetic saturation, leading to inaccurate readings.
Innovation Solution
A self-oscillating current sensor device with a resampling mechanism that uses a duty ratio calculation, clock introduction, and low-pass filtering to accurately distinguish between direct and alternating currents, employing a magnetic core with a ring shape and a self-oscillating circuit to generate pulse signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a self-oscillating circuit with magnetic core is used to detect current, then the device can generate pulse signals to detect current flowing through the primary conductor, but the magnetic core becomes magnetically saturated when large amplitude alternating current flows, causing erroneous detection of alternating current as direct current
Solution Approach 1:
The patent introduces a resampling portion as an intermediary between the duty ratio calculation portion and the low-pass filter. This resampling portion converts the duty ratio signal from variable frequency (linked to oscillation frequency) to a fixed sampling frequency using a clock signal, thereby decoupling the detection system from the oscillation frequency variations caused by magnetic saturation and preventing erroneous detection of alternating current components.
2Productivity
If the oscillation frequency of the self-oscillating circuit varies with current amplitude, then the device responds to current variations, but the variable frequency causes the low-pass filter to erroneously integrate alternating current components as direct current
Solution Approach 1:
The patent changes the sampling frequency parameter from variable (linked to oscillation frequency) to fixed (based on clock signal) through the resampling portion. This parameter change ensures that the low-pass filter operates with a constant integration frequency, preventing the erroneous conversion of alternating current components to direct current while maintaining the ability to respond to current variations through the duty ratio signal.
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 device effectively differentiates between direct and alternating currents by resampling the duty ratio signal at a constant frequency, preventing erroneous detection of alternating current as direct current, even in conditions of magnetic saturation.
Implementation Method 1
The self-oscillating circuit has a magnetic core with a ring shape. The primary conductor extends through a central hole of the magnetic core. The self-oscillating circuit generates a pulse signal in response to the current flowing through the primary conductor
Implementation Method 2
the magnetic core may become magnetically saturated when the current flowing through the primary conductor includes a large amplitude alternating current component
Data Source
AI summary
A current sensor device comprises a self-oscillating circuit, a duty ratio calculation portion, a clock introducing portion, a resampling portion and a low-pass filter. The self-oscillating circuit has a magnetic core with a ring shape. A primary conductor extends through a central hole of the magnetic core. The self-oscillating circuit generates a pulse signal in response to a current flowing through the primary conductor and operates based on the pulse signal. The duty ratio calculation portion calculates a duty ratio of the pulse signal and outputs a duty ratio signal. The clock introducing portion generates a clock signal having a constant frequency. The resampling portion resamples the duty ratio signal based on the clock signal. The low-pass filter integrates the resampling signal.