Segmented Ferromagnetic Core Current Transducer for Leakage Detection
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Solution Overview
Problem
Current clamp-on current transducers face limitations in measuring low electrical currents due to noise and external magnetic field interference, and are sensitive to the position of the cable within the ferromagnetic core, making them inadequate for detecting and localizing current leakage paths in electrical machines.
Innovation Solution
A magnetic transducer with two ferromagnetic cores positioned parallel to each other and rotated by a predetermined angle, equipped with magnetic field sensors and an electronic circuit that includes a transformer, fully differential preamplifier, and phase sensitive detector, capable of measuring low-frequency magnetic fields and immune to external disturbances, allowing for precise detection of low electrical currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single ferromagnetic core with one magnetic sensor is used, then the device complexity is low, but the measurement precision deteriorates due to noise and external magnetic field interference
Solution Approach 1:
The single ferromagnetic core is divided into multiple segments (first, second, third, and fourth ferromagnetic cores) with sensors positioned at different locations. This segmentation allows the system to measure magnetic fields from multiple perspectives, improving measurement precision by reducing the impact of noise and external interference while maintaining manageable device complexity through modular construction.
2Object-affected harmful factors
If magnetic sensors are placed at different air gaps of the same core, then the immunity to external magnetic fields improves, but the device complexity increases
Solution Approach 1:
Instead of using a single complex core structure, the invention segments the magnetic measurement system into multiple separate ferromagnetic cores, each with its own air gap and sensor. This approach improves immunity to external magnetic fields by distributing measurement points across different spatial locations, while the modular nature of separate cores keeps the overall device complexity manageable through standardized components.
3Ease of operation
If the cable position is not precisely controlled, then the ease of operation improves, but the measurement precision deteriorates due to position dependence
Solution Approach 1:
The magnetic measurement is segmented into multiple independent measurement points at different air gaps. By taking measurements from multiple locations around the cable, the system compensates for position-dependent variations in a single measurement point. This allows the cable to be positioned more freely while maintaining measurement precision through computational integration of multiple sensor readings.
4Measurement precision
If very low currents are measured, then the measurement precision improves for low-current detection, but the device becomes more sensitive to noise and external fields
Solution Approach 1:
The measurement system is segmented into multiple sensors positioned at different air gaps, each contributing to the overall measurement of low currents. By combining signals from multiple segmentation points, the system achieves the sensitivity needed for low-current detection while the spatial distribution of sensors provides inherent noise rejection and immunity to external magnetic field interference.
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 solution enables the measurement of very low DC and AC currents down to 1 µA with high immunity to external magnetic fields and reduced sensitivity to cable position, effectively detecting and localizing current leakage paths in electrical machines.
Implementation Method 1
a combination of a ferro-magnetic core, which encloses a current-carrying cable, and a magnetic transducer
Implementation Method 2
measuring the magnetic field produced by the current
Data Source
Figure 1~2
Figure 3~4
Figure 5~9
AI summary
The invention concerns a current transducer for measuring a current flowing through a cable, comprising at least one magnetic field sensor and an electronic circuit. The current transducer comprises a head (40) with at least two ferromagnetic cores (46) optimized to reduce the effects of external magnetic fields. The current transducer optionally comprises a magnetic transducer comprising a magnetic field sensor and an electronic circuit. The electronic circuit comprises at least one current source (2), a transformer (3), a fully differential preamplifier (4) coupled to the transformer (3), a phase sensitive detector (6) coupled to the preamplifier (4) and a logic block (5, 5a) configured to operate the magnetic field sensor(s) to provide an AC output voltage. The magnetic field sensor(s) is preferably either a Hall element (1) or an AMR sensor (19) or a flux-gate sensor.