Rigid Conductor Bus Bar for Ground Fault Sensor Accuracy
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Solution Overview
Problem
Ground Fault Interrupter sensors experience inaccuracies due to uneven magnetic fields caused by improper conductor placement, leading to load shift errors, which are typically compensated by twisting conductors but can be improved upon.
Innovation Solution
The use of a rigid conductor surrounding an insulated flexible conductor to create a 'faux coax bus bar' arrangement within the current transformer, controlling current flow and magnetic field distribution to reduce load shift errors and provide consistent performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conductors are not located properly in the sensor, then uneven magnetic fields are generated causing load shift errors, but twisting conductors to compensate increases device complexity
Solution Approach 1:
A magnetic shield is introduced as an intermediary component between the conductors and the sensor core. This shield mediates the magnetic field distribution, creating more uniform fields that reduce load shift errors without requiring complex conductor twisting arrangements
Solution Approach 2:
The magnetic shield changes the magnetic field parameters (distribution and uniformity) by providing a controlled magnetic path. This alters the field characteristics to reduce measurement errors while maintaining simple conductor routing
2Ease of manufacture
If rigid tubular conductor is used instead of twisted pair, then manufacturing is simplified and routing consistency is improved, but control over current flow distribution is reduced
Solution Approach 1:
The magnetic shield acts as an intermediary that compensates for the lack of current flow control in rigid conductors. It ensures proper magnetic field distribution even though the rigid conductor structure itself cannot be twisted or adjusted
Solution Approach 2:
The magnetic shield provides localized magnetic path control at critical points within the sensor. This allows precise control of magnetic field characteristics in specific regions without requiring the entire conductor assembly to be complex or adjustable
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
This arrangement enhances the accuracy of current sensor output by evenly distributing magnetic fields and current flow, reducing load shift errors and simplifying construction while maintaining consistent routing paths for improved ground fault detection.
Implementation Method 1
Each current carrying conductor will produce a magnetic flux which is in compliance with the 'Right Hand Rule' used to determine flux direction
Implementation Method 2
The current flow direction of the power conductors and the neutral conductors are in the opposite directions when they are routed through the Ground Fault current transformer 17 sensor housing
Implementation Method 3
The rigid conductor may be shaped to provide controlled current flow distribution for adjusting any ground fault load shift through the current transformer and more evenly distributing the magnetic field through the current transformer
Data Source
AI summary
The line power and neutral conductors for a circuit interrupter such as a miniature circuit breaker, using ground fault sensing via a current transformer, are arranged as a rigid conductor formed from a flat plate and surrounding and holding an insulated flexible conductor when passing through the Ground Fault Interrupter current transformer. The rigid conductor can provide a shaped current path to maximize the effectiveness of the current transformer.