Air-Cored Coil Current Detection in Ferromagnetic Tank
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional current detection devices face accuracy issues due to changing magnetic properties in ferromagnetic tanks, which affect the correction of superimposed phase currents, leading to inaccurate current detection.
Innovation Solution
A current detection device with air-cored coils attached to phase conductors, supported by an insulator and housed in a ferromagnetic tank, incorporates output-voltage detection circuits and a correction processing circuit that calculates and applies voltage correction values based on current value levels to accurately determine phase currents, using transformation ratios and voltage correction factors adjusted for current magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional correction processes using fixed correction factors are applied, then the device structure remains simple, but measurement precision deteriorates when current magnitude changes
Solution Approach 1:
The correction factors are made dynamic rather than fixed. The correction processing circuit calculates correction factors in real-time based on the output voltages from air-cored coils, allowing the correction to adapt to changing current magnitudes and magnetic flux distribution conditions in the ferromagnetic tank.
Solution Approach 2:
The system uses feedback from the output voltages of the air-cored coils to continuously adjust the correction factors. The correction processing circuit monitors the actual output voltages and computes appropriate correction factors based on these feedback signals, enabling accurate current measurement across varying conditions.
2Strength
If ferromagnetic tank is used for housing conductors, then structural strength and insulation are improved, but magnetic flux distribution becomes non-linear and current detection accuracy deteriorates
Solution Approach 1:
Air-cored coils are introduced as intermediary sensing elements that wrap around the phase conductors inside the ferromagnetic tank. These coils provide a measurement path that is less sensitive to the ferromagnetic material's non-linear magnetic properties, allowing accurate current detection despite the tank's magnetic characteristics.
Solution Approach 2:
The system changes the measurement parameter from direct magnetic field measurement to voltage measurement across the air-cored coils. By measuring the voltage induced in the air-cored coils and applying dynamic correction factors, the system compensates for the ferromagnetic tank's non-linear magnetic flux distribution.
3Measurement precision
If correction is performed using fixed correction factors, then processing speed is maintained, but measurement precision deteriorates when current magnitude varies
Solution Approach 1:
The correction processing circuit performs preliminary calculations by continuously monitoring output voltages and pre-computing appropriate correction factors. This preliminary action ensures that when current measurement is needed, the correction factors are already optimized for the current conditions, maintaining both accuracy and processing efficiency.
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 high-accuracy current detection irrespective of current magnitude, even in ferromagnetic environments where magnetic flux distribution changes non-linearly with current strength.
Implementation Method 1
a plurality of air-cored coils (2a, 2b, 2c) that are attached to conductors (1a, 1b, 1c) for a plurality of phases, respectively
Implementation Method 2
housed in a tank (5) made of a ferromagnetic material
Data Source
AI summary
The current detection device includes a plurality of air-cored coils respectively attached to conductors for a plurality of phases, which are supported by an insulator and housed in a ferromagnetic tank a plurality of output-voltage detection circuits that detect output voltages of the air-cored coils for respective phases; and a correction processing circuit that obtains, by dividing the output voltages of the air-cored coils for respective phases by transformation ratios of the air-cored coils, current value levels, which are temporary values of currents flowing in the conductors for respective phases, calculates the output-voltage correction values for respective phases according to the current value levels of respective phases, and calculates and outputs current flowing in the conductors for respective phases on the basis of the output-voltage correction values.