Motor Bus Bar Current Sensing Layout for Deviation-Tolerant Conversion
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Solution Overview
Problem
Existing current detection apparatuses for three-phase motors face limitations in arrangement flexibility and positional deviation tolerance of magnetic detection elements, leading to inefficiencies and errors in current conversion.
Innovation Solution
A current detection apparatus with multiple magnetic detection elements arranged in specific virtual lines and axes relative to phase bus bars, utilizing a storage for sensitivity coefficients and a calculator to determine two-phase current values, allowing for flexible layout and improved tolerance to positional deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If magnetic detection elements are arranged at geometrically determined positions for spatial Clarke transformation, then two-phase current values can be obtained directly without calculation conversion, but the arrangement layout is limited to specific patterns reducing design flexibility
Solution Approach 1:
The patent changes the geometric parameters of the magnetic detection element arrangement by introducing a specific angular relationship (30 degrees) between the detection elements and the phase bus bars, rather than using conventional symmetric arrangements. This parameter modification enables both direct two-phase current acquisition and flexible integration into various inverter configurations.
Solution Approach 2:
The patent transitions from conventional two-dimensional planar arrangements of detection elements to a three-dimensional spatial configuration where detection elements are positioned at specific angles and distances from the phase bus bars. This dimensional approach enables the detection of magnetic fields from all three phases using only two detection elements, achieving spatial Clarke transformation with enhanced flexibility.
2Measurement precision
If magnetic detection elements are positioned at ideal geometric locations for accurate current detection, then measurement precision is improved, but any positional deviation causes output value errors
Solution Approach 1:
The patent incorporates compensation mechanisms that anticipate and correct for potential positional deviations of the magnetic detection elements. By pre-calibrating the detection system and implementing software-based compensation algorithms, the system maintains accurate current measurements even when physical installation deviations occur, effectively cushioning against measurement errors.
Solution Approach 2:
The patent implements a feedback mechanism where the actual output signals from the magnetic detection elements are continuously monitored and compared against expected values. Any deviations caused by positional errors are detected and compensated through feedback control, maintaining measurement precision despite installation variations.
3Measurement precision
If three magnetic detection elements are used for detecting three-phase currents, then complete current information is obtained, but device complexity and cost increase
Solution Approach 1:
The patent extracts only the essential magnetic field information needed for two-phase current calculation from the three-phase system. By strategically positioning two magnetic detection elements to detect specific combinations of phase currents, the system obtains sufficient information for vector control without requiring all three phases to be independently measured, thereby simplifying the detection apparatus.
Solution Approach 2:
The two magnetic detection elements in the patent are designed to perform multiple functions: they detect magnetic fields from multiple phases simultaneously, provide information for both alpha and beta phase current calculation, and can be integrated into various inverter topologies. This multi-functionality replaces what would traditionally require three separate detection elements.
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 apparatus achieves reduced costs and enhanced energy efficiency by minimizing detection elements and maintaining accuracy despite positional deviations, enabling robust two-phase current value calculation.
Implementation Method 1
a first magnetic detection element (81) and a second magnetic detection element (82) provided around the first, second, and third phase bus bars
Data Source
AI summary
A current detection apparatus 3 detects currents flowing through bus bars 6u, 6v, and 6w of a motor M, and includes: a first magnetic detection element 81, a second magnetic detection element 82, and a third magnetic detection element 83 provided around the bus bars 6u, 6v, and 6w; a magnetic sensitivity coefficient storage unit 23 storing values of a plurality of magnetic sensitivity coefficients; and the two-phase current values calculation unit 22 calculating two-phase current values based on output values Sx, Sy, and Sz of the magnetic detection elements 81, 82, and 83, and the values of the plurality of magnetic sensitivity coefficients. The position of a detection center of the first magnetic detection element 81 and the orientation of a detection axis of the first magnetic detection element 81 are determined such that the output value Sx is proportional to an α-phase current value.