Integrated Common-Mode Choke for AC Bus Current Sensing

Solution Overview

Problem

Multi-phase AC machines experience undesirable induced currents due to common mode voltages, which are challenging to measure accurately and efficiently without increasing system mass or packaging dimensions, particularly in compact systems like automotive applications.

Innovation Solution

An AC motor system incorporating an AC choke surrounding the AC bus and a current sensor with a coil proximate to the AC choke, which includes a shunt resistor and voltage integrator to determine common mode current, allowing for adjustments in pulse width modulation and slew rate to mitigate these currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If cored current sensors or current transformer measurements are used to measure common mode current, then common mode current can be measured, but system mass and packaging dimensions increase

Engineering Contradiction:

Improvecommon mode current measurementVSAvoidsystem mass

Core Design Contradiction:

Measurement precisionVSWeight of stationary object

Solution Approach 1:

The patent combines the current transformer core with the AC choke into a single integrated component. The AC choke serves dual purposes: it provides common mode current attenuation functionality and simultaneously acts as the core for measuring common mode current. This merging eliminates the need for separate current sensing cores, thereby reducing system mass and packaging dimensions while maintaining measurement capability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The AC choke is designed to perform multiple functions: it attenuates common mode currents in the power inverter output and simultaneously serves as the sensing core for measuring common mode current through a wound coil. This multi-functionality reduces the number of separate components needed, decreasing overall system mass and packaging requirements

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If cored current sensors or current transformer measurements are used to measure common mode current, then common mode current can be measured, but packaging volume increases

Engineering Contradiction:

Improvecommon mode current measurementVSAvoidpackaging volume

Core Design Contradiction:

Measurement precisionVSVolume of stationary object

Solution Approach 1:

The patent combines the current transformer core with the AC choke into a single integrated component. The AC choke serves dual purposes: it provides common mode current attenuation functionality and simultaneously acts as the core for measuring common mode current. This merging eliminates the need for separate current sensing cores, thereby reducing system mass and packaging dimensions while maintaining measurement capability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The coil for sensing common mode current is wound around or integrated within the AC choke structure. This nesting arrangement allows the sensing element to be contained within the space already occupied by the choke, eliminating the need for additional external packaging volume for separate sensing components

Inventive Principle:

Principle #7Nested doll (Nesting)

3Measurement precision

If separate current sensing cores are used, then common mode current can be measured, but length of the buses increases

Engineering Contradiction:

Improvecommon mode current measurementVSAvoidbus length

Core Design Contradiction:

Measurement precisionVSLength of moving object

Solution Approach 1:

The patent combines the current transformer core with the AC choke into a single integrated component. The AC choke serves dual purposes: it provides common mode current attenuation functionality and simultaneously acts as the core for measuring common mode current. This merging eliminates the need for separate current sensing cores, thereby reducing system mass and packaging dimensions while maintaining measurement capability

Inventive Principle:

Principle #5Merging (Combining)

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

Effectively attenuates common mode currents, reduces packaging volume, and enhances system performance and longevity by accurately measuring and controlling these currents without increasing system mass or dimensions.

Implementation Method 1

an AC choke surrounding the AC bus

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

a current sensor including a coil proximate the AC choke

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS12500484B2Integrated common mode choke and current sensing

Publication Date: 2025.12.16 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

An alternating current (AC) motor system includes an AC motor with a rotor and a stator with multi-phase AC stator windings. The system also includes a power inverter that generates a multi-phase AC voltage, an AC bus that connects the power inverter to the stator windings, an AC choke that surrounds the AC bus, and a current sensor with a coil wound on or surrounded by the AC choke. The current sensor measures common mode current in the AC bus, and is used in pulse width modulation or slew rate control of the power inverter, ensuring smooth operation and reducing the risk of damage due to common mode current.