Brush Holder Hall Sensor Layout for Shielded Current Measurement
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Solution Overview
Problem
Current methods for monitoring the current passing through brushes in rotating electrical machines are either inefficient, prone to interference from external magnetic fields, or require complex installations, making them unreliable and difficult to implement effectively.
Innovation Solution
A current sensor device featuring a Hall effect sensor and a concentrator that focuses the magnetic field generated by the current passing through the brush, allowing for accurate measurement while protecting the sensor from external magnetic influences, and is designed to be compact and easy to mount.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Hall effect sensor is mounted on the cable supplying the brush, then the current measurement is non-intrusive, but the sensor is exposed to external magnetic fields causing disturbances and losses
Solution Approach 1:
The patent introduces a magnetic concentrator as an intermediary element between the brush and the Hall effect sensor. This concentrator guides and concentrates the magnetic field lines generated by the brush current toward the sensor, while simultaneously shielding the sensor from external magnetic field disturbances. The concentrator acts as a mediator that selectively enhances the desired magnetic field signal while filtering out harmful external interference.
Solution Approach 2:
The patent extracts the Hall effect sensor from its conventional mounting location on the cable and repositions it within the brush holder structure. This extraction allows the sensor to be positioned in a location where it can measure the magnetic field generated by the brush current while being protected from external magnetic field sources by the brush holder and concentrator assembly.
2Ease of manufacture
If a current sensor resistor is used to monitor brush current, then the system is inexpensive and simple, but current loss occurs and monitoring each brush is difficult due to large device size
Solution Approach 1:
The patent replaces the conventional current sensor resistor (mechanical/electrical contact-based measurement) with a Hall effect sensor that operates on electromagnetic principles. This substitution eliminates the need for physical contact with the current path, thereby eliminating current loss through the sensor while maintaining measurement capability. The Hall effect sensor detects the magnetic field generated by the brush current without drawing any current itself.
3Power
If multiple brushes are electrically connected in parallel to handle high power, then the current distribution becomes asymmetric causing some brushes to overheat or act as abrasive stones, but monitoring each brush individually increases device complexity
Solution Approach 1:
The patent applies segmentation by providing a separate current sensor device for each brush rather than using a single monitoring system for all brushes. Each brush holder with its brush is equipped with its own Hall effect sensor and concentrator assembly, allowing independent monitoring of current through each brush. This segmentation enables individual brush current measurement while maintaining relatively simple device structures that can be replicated for each brush.
4Measurement precision
If a Hall effect sensor is positioned to measure brush current, then accurate measurement is achieved, but the sensor must be precisely positioned within the magnetic field which increases installation difficulty
Solution Approach 1:
The magnetic concentrator serves as an intermediary that shapes and directs the magnetic field lines toward the Hall effect sensor. This concentrator relaxes the positioning requirements for the sensor by actively guiding the magnetic field lines to pass through the sensor's sensitive area, making the installation process more forgiving of positioning variations while maintaining measurement accuracy.
Solution Approach 2:
The concentrator is pre-installed on the brush holder before the Hall effect sensor is positioned. This preliminary action creates a predetermined magnetic field pathway that guides the field lines to the sensor's optimal measurement position, simplifying the subsequent sensor installation process and ensuring accurate positioning without requiring complex alignment procedures.
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 reliable, efficient, and accurate monitoring of current through each brush, reducing interference and simplifying installation, enabling precise measurement of high currents up to 600 A with high accuracy.
Implementation Method 1
A Hall effect sensor is sensitive to the magnetic flux created by a flow of current and generates a voltage representative of this current
Implementation Method 2
a concentrator arranged to concentrate the magnetic fields inside a concentrated magnetic field zone and to protect this zone from the external magnetic fields
Data Source
AI summary
The invention relates to a current sensor device for monitoring the current flowing through a brush, comprising: —a brush holder (12) extending in a longitudinal direction and defining a through-housing intended to accommodate a brush such that one end of the brush which is intended to brush against a rotating movable surface protrudes from the brush holder, a Hall effect sensor (14) arranged to detect a magnetic field; —a concentrator (16) for concentrating the magnetic fields in a concentrated magnetic field zone and for protecting the zone from external magnetic fields, in which: —the concentrator (16) is mounted on the brush holder (12) so as to surround at least part of the housing of the brush holder; —the Hall effect sensor is mounted on the brush holder (12) at a position located inside the concenrated magnetic field zone.