AC Component Detection in DC Circuits Using Segmented Inductor-Capacitor Paths
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Solution Overview
Problem
Conventional current sensors for detecting AC components in DC circuits face challenges with sensitivity and linearity, especially at low frequencies and high DC currents, due to magnetic core saturation and size/cost issues, and are not well-suited for measuring small AC components at low frequencies.
Innovation Solution
A device with an inductor and capacitor series circuit in parallel with a transformer, along with a low-pass filter circuit, separates AC and DC components, allowing for high sensitivity and accuracy detection of AC components without core saturation concerns, using a smaller transformer and reducing component size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic core material with high permeability is used in current sensors to increase sensitivity for detecting small AC components, then the sensitivity and linearity of the sensor is improved, but the core material becomes saturated at high DC current strengths
Solution Approach 1:
The circuit is segmented into two parallel paths: a DC path with an inductor for carrying high DC currents, and an AC path with a capacitor and transformer for detecting AC components. This segmentation allows each path to be optimized independently - the DC path handles high currents without saturation while the AC path provides high sensitivity for AC detection.
Solution Approach 2:
A capacitor is introduced as an intermediary element in the AC path that blocks DC currents while allowing AC signals to pass through to the transformer. This intermediary enables the separation of DC and AC current paths, allowing the transformer to operate without DC saturation while maintaining high sensitivity for AC component detection.
2Reliability
If the volume of the magnetic core is increased to avoid saturation at high DC current strengths, then core saturation is prevented, but the size and manufacturing costs of the sensor increase
Solution Approach 1:
The circuit is segmented into two parallel paths: a DC path with an inductor for carrying high DC currents, and an AC path with a capacitor and transformer for detecting AC components. This segmentation allows each path to be optimized independently - the DC path handles high currents without saturation while the AC path provides high sensitivity for AC component detection.
Solution Approach 2:
A capacitor is introduced as an intermediary element in the AC path that blocks DC currents while allowing AC signals to pass through to the transformer. This intermediary enables the separation of DC and AC current paths, allowing the transformer to operate without DC saturation while maintaining high sensitivity for AC component detection.
3Measurement precision
If the number of turns in the coil is increased to increase inductance for detecting low-frequency AC components, then the sensitivity for low-frequency detection is improved, but the size and costs of the sensor increase
Solution Approach 1:
The circuit configuration is changed by introducing a capacitor in series with the transformer primary winding, creating a high-pass filter that enhances low-frequency AC signal transmission to the transformer. This parameter change allows the use of fewer turns in the transformer while maintaining sensitivity for low-frequency detection, thereby reducing the overall size and cost of the sensor.
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 achieves high sensitivity and accuracy in detecting AC components across a wide frequency range with reduced component size and cost, while maintaining a linear transfer function, effectively addressing the limitations of conventional sensors.
Implementation Method 1
an inductor which is conductive for a direct-current component, but which constitutes a frequency-dependent resistor for an alternating-current component
Implementation Method 2
a series circuit made up of a capacitor and a primary winding of a transformer
Implementation Method 3
a primary winding of a transformer
Implementation Method 4
a low-pass filter circuit, wherein a secondary winding of the transformer is connected to the voltage measuring device via the low-pass filter circuit
Data Source
AI summary
A device for detecting alternating-current components iAC of an electric current iACDC flowing in a direct-current circuit includes an inductor arranged in the direct-current circuit, and an AC path arranged electrically in parallel with the inductor, wherein the AC path comprises a series circuit made up of a capacitor and a primary winding of a transformer. The device further includes a voltage measuring device, wherein a secondary winding of the transformer is connected to the voltage measuring device via a low-pass filter circuit.