Differential Current Sensor Using Magnetic Field Sensing Elements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional ground fault interrupter (GFI) devices are bulky and expensive due to their reliance on differential current transformers, which require costly and complex wiring setups for phase and neutral conductor connections.
Innovation Solution
A differential current sensor with integrated magnetic field sensing elements and circuitry that measures the difference and absolute currents between phase and neutral conductors, allowing for a compact, low-cost design with programmable misalignment compensation and integrated coil driver for trip circuit actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a differential current transformer is used to detect current imbalance in GFI devices, then the device can reliably detect ground faults, but the device becomes bulky and expensive
Solution Approach 1:
The patent replaces the mechanical differential current transformer with magnetic field sensing elements (such as Hall effect sensors or magnetoresistive sensors) that directly sense the magnetic field generated by current flow. This substitution eliminates the bulky transformer structure while maintaining the ability to detect current differences through magnetic field measurements, thereby reducing device size and cost while preserving ground fault detection accuracy
Solution Approach 2:
The magnetic field sensing elements serve multiple functions: they detect both the magnitude and direction of current flow in phase and neutral conductors, enable differential current measurement for ground fault detection, and can potentially provide additional functionality such as angle sensing and redundancy. This multi-functionality consolidates what would otherwise require separate components into a single sensing mechanism
2Measurement precision
If a differential current transformer is used for current measurement, then accurate differential current detection is achieved, but the wiring setup becomes costly and complex
Solution Approach 1:
The patent replaces the transformer-based measurement system with direct magnetic field sensing using integrated circuit sensors. These sensors can be positioned close to the conductors and provide accurate differential current measurements through electronic signal processing, eliminating the need for complex transformer winding configurations and associated wiring challenges
Solution Approach 2:
The magnetic field serves as an intermediary between the current flow and the sensing elements. Instead of directly measuring current through electrical connections that require complex wiring, the sensors measure the magnetic field generated by the current, which can be done through simple proximity placement. This intermediary approach simplifies the physical connection requirements while maintaining measurement accuracy
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 provides accurate and cost-effective differential current sensing, enabling miniaturization of GFI modules with reduced assembly complexity and potential for additional functionalities like redundancy and angle sensing, while compensating for mechanical misalignment.
Implementation Method 1
magnetic field sensing elements including a first sensing element to sense a magnetic field associated with a first current carried by a first current conduction path and a second sensing element to sense a magnetic field associated with a second current carried by a second current conduction path
Implementation Method 2
The circuitry can operate to generate first and second signals based on the sensed first and second magnetic fields, respectively
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A sensor with multiple magnetic field sensing elements for use in current sensing and other applications is presented. In one configuration, the sensor obtains differential and absolute current measurements of current in current-carrying conductors. When employed in a ground fault interrupter application, a first magnetic field sensing element is used to measure the absolute current flowing in the phase conductor (phase current), a second magnetic field sensing element is used to measure the absolute current flowing in the neutral conductor (neutral current) and a difference between the phase and neutral currents is measured by a third magnetic field sensing element or determined from measurements of the first and second magnetic field sensing elements. In another configuration, a measure of the difference between currents and/or the sum of currents in current-carrying conductors can be obtained. An arrangement of multiple sensing elements may be used for misalignment detection/correction.