Integrated Current Sensing for Common-Mode Noise on Inverter Buses
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Solution Overview
Problem
Existing current sensing technologies for DC and AC buses in inverter-controlled rotary electric machines face challenges in minimizing bus length and system mass while effectively measuring and reducing noise/parasitic currents induced by power inverter switching.
Innovation Solution
A current sensing apparatus featuring a common mode core surrounding multiple current conductors and integrated with differential mode cores, allowing for the measurement of both common mode and differential mode currents without increasing system mass or packaging dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current sensors are added to measure bus currents, then measurement capability is improved, but system mass and packaging volume increase
Solution Approach 1:
The patent combines common mode current sensing and differential mode current sensing into a single integrated sensor assembly. The common mode core and differential mode cores share a unified magnetic circuit structure, allowing multiple measurement functions to be achieved without proportionally increasing system mass. This merging approach enables the system to measure both common mode currents (for EMI reduction) and differential mode currents (for control purposes) using one integrated device rather than separate sensors.
Solution Approach 2:
The integrated current sensing apparatus performs multiple functions simultaneously: it measures common mode currents on DC and AC buses for EMI reduction, measures differential mode currents for inverter control, and provides magnetic shielding. The single sensor assembly serves as both a measurement device and an EMI mitigation device, eliminating the need for separate common mode chokes and current sensors.
2Measurement precision
If current sensors with finite packaging volume are added, then measurement capability is improved, but bus length increases
Solution Approach 1:
The sensor assembly is designed to nest around existing bus structures. The common mode core surrounds multiple bus conductors (DC+ and AC phase conductors) in a compact configuration, with differential mode cores integrated within or adjacent to the common mode core. This nested arrangement allows the sensor to encompass multiple current carriers without requiring additional linear space along the bus path.
Solution Approach 2:
Instead of extending bus length linearly to accommodate separate sensors, the patent uses a three-dimensional integrated core structure where common mode and differential mode sensing functions are stacked or arranged in adjacent spatial dimensions. The cores share magnetic pathways and physical space, transforming a linear space requirement into a compact volumetric arrangement that does not extend bus length.
3Measurement precision
If separate common mode cores and differential mode cores are used, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges common mode core and differential mode core functions into a single integrated magnetic assembly. The common mode core provides a magnetic path for common mode flux, while differential mode cores (integrated within or adjacent to the common mode core) provide separate magnetic paths for differential mode flux measurement. This integration reduces the number of discrete components, simplifies assembly, and reduces overall device complexity while maintaining separate measurement channels for both current modes.
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 effectively measures and reduces parasitic currents, minimizing electromagnetic interference and system noise while maintaining compact dimensions and low mass.
Implementation Method 1
Current sensors may employ closed or open ferrous cores to concentrate flux to and/or shield current sensing elements from stray magnetic influences
Implementation Method 2
Current sensing elements placed near current carriers such as DC bus conductors or AC bus conductors
Data Source
AI summary
A current sensing apparatus may include a common mode core surrounding two or more current conductors and a current sensing element proximate the common mode core.