Busbar Hole Current Sensing Without Ferromagnetic Cores
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Solution Overview
Problem
Current sensing systems in electric vehicles using bulky ferromagnetic cores are costly, heavy, limit bandwidth, and introduce hysteresis errors, while coreless solutions increase resistance and Joule heating.
Innovation Solution
A current sensing system with sensing points located at a hole in the busbar, using a coordinate axis system to measure magnetic fields, and an operational amplifier to amplify the difference between these points, eliminating the need for bulky cores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bulky ferromagnetic core is used in the current sensing system, then the magnetic field concentration and sensing capability are improved, but the weight, fabrication cost, and device complexity increase
Solution Approach 1:
The patent removes the bulky ferromagnetic core from the current sensing system and replaces it with a coreless design. The sensing function is achieved by measuring the magnetic field directly at strategic locations around the busbar using multiple sensing points, eliminating the need for the core structure while maintaining sensing capability.
Solution Approach 2:
The patent replaces the mechanical ferromagnetic core structure with an electronic measurement system. Instead of using magnetic materials to concentrate and guide flux, the system uses multiple electronic sensing points to directly measure magnetic field components, substituting the mechanical core with an electronic detection and processing system.
2Measurement precision
If a bulky ferromagnetic core is used in the current sensing system, then the magnetic field concentration is improved, but the bandwidth is limited
Solution Approach 1:
The patent extracts the ferromagnetic core that was limiting the bandwidth and replaces it with a coreless design. This removal of the magnetic core eliminates the hysteresis and saturation effects that constrained the bandwidth, allowing the system to accurately measure higher frequency current variations.
3Measurement precision
If a bulky ferromagnetic core is used in the current sensing system, then the magnetic field concentration is improved, but hysteresis errors are introduced
Solution Approach 1:
The patent removes the ferromagnetic core that causes hysteresis losses and replaces it with a coreless measurement system. By eliminating the magnetic core, the system avoids hysteresis errors entirely, as there is no magnetic material to exhibit hysteresis behavior during cyclic magnetic field changes.
4Weight of moving object
If a coreless solution with a notch is used in the busbar, then the weight and fabrication cost are reduced, but the resistance and Joules heating increase
Solution Approach 1:
The patent removes the need for both the ferromagnetic core and the busbar notch by implementing a different sensing approach. The sensing points are positioned to measure the magnetic field generated by the busbar current without requiring any structural modifications to the busbar itself, thereby avoiding increased resistance and Joule heating.
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 system effectively measures current without bulky cores, reducing fabrication costs and weight, while maintaining high bandwidth and minimizing hysteresis errors.
Implementation Method 1
a first sensing point (11) mounted at a left side of a mid-wideness line (MWL) which is set as a z axis, wherein the first sensing point (11) is configured to measure a magnetic field generated by the current flowing through the busbar in a z direction
Implementation Method 2
an operational amplifier (13) configured to amplify a difference between an output of the first sensing point (11) and an output of the second sensing point (12), to generate an amplified signal (AMP)
Data Source
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AI summary
A current sensing system mounted at a hole located approximately in a busbar center is discussed. The current sensing system has a first sensing point, a second sensing point and an operational amplifier. The first sensing point and the second sensing point are located along a mid-thickness line of the busbar with a substantially equal distance from the mid-wideness line of the busbar.