PWM-Controlled Multiphase Windings for Common-Mode Emission Cancellation

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Solution Overview

Problem

Electrical power systems in aircraft hybrid-electric propulsion systems face increased common mode emissions due to higher power distribution voltages and parasitic currents, leading to voltage stresses and electromagnetic interference.

Innovation Solution

The implementation of polyphase or multiphase windings in electric machines that operate under complementary excitation, combined with PWM signal synthesis at the power converter system, to cancel common mode emissions by generating opposite polarity signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If power distribution voltage is increased in aircraft hybrid-electric propulsion systems, then power transmission efficiency is improved, but common mode emissions increase causing voltage stresses and parasitic currents

Engineering Contradiction:

Improvepower transmission efficiencyVSAvoidcommon mode emissions

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by generating counter-phase PWM signals before they can cause harmful common mode emissions. The control system synthesizes PWM signals with opposite polarity that preemptively cancel each other's common mode components, preventing the emissions from affecting electromechanical interfaces rather than treating them after occurrence.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent converts the harmful common mode emissions into a beneficial cancellation effect. By deliberately generating opposite phase PWM signals, the system transforms what would be harmful electromagnetic interference into a self-cancelling phenomenon, where the emissions from one phase are neutralized by equal and opposite emissions from another phase.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Object-affected harmful factors

If EMI filters are added to reduce common mode emissions, then electromagnetic interference is mitigated, but system weight increases

Engineering Contradiction:

Improveelectromagnetic interferenceVSAvoidsystem weight

Core Design Contradiction:

Object-affected harmful factorsVSWeight of moving object

Solution Approach 1:

The patent replaces the mechanical/electrical EMI filter system with a control-based solution. Instead of using physical filtering components to block common mode emissions, the system uses software-controlled PWM signal synthesis to actively cancel emissions at their source, substituting a control algorithm for traditional electromagnetic filtering hardware.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system performs self-service by generating its own counter-phase signals to neutralize harmful emissions. The power converter system creates and controls its own PWM signals, which inherently contain the cancellation capability, eliminating the need for external EMI filters or additional mitigation components.

Inventive Principle:

Principle #25Self-service

3Reliability

If shaft grounding brushes and bearing insulation are installed to protect against shaft voltage, then component reliability is improved, but device complexity increases

Engineering Contradiction:

Improvecomponent reliabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the need for shaft grounding brushes and bearing insulation by addressing the root cause of shaft voltage. By canceling common mode emissions at the power converter level, the system removes the harmful voltage sources that would otherwise require protective components, extracting these unnecessary elements from the system design.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system takes preliminary action by preventing shaft voltage from occurring in the first place. Through proactive common mode cancellation, the patent eliminates the formation of harmful voltages before they can affect shaft-mounted components, making protective measures like grounding brushes and bearing insulation unnecessary.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP4170897B1Reduction of common mode emission of an electrical power converter

Publication Date: 2026.04.08 GENERAL ELECTRIC CO

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AI summary

A power system (400, 500) including a power converter system (410, 510) and an electric machine (450, 550) is provided. In one aspect, the power converter system (410, 510) has first and second switching elements (412, 512). The electric machine (450, 550) includes a first multiphase winding (461, 561) electrically coupled with the first switching elements (411, 511) and a second multiphase winding (462, 562) electrically coupled with the second switching elements (412, 512). The first and second multiphase windings (462, 562) are arranged and configured to operate electrically opposite in phase with respect to one another. One or more processors (960A) control the first switching elements (411, 511) to generate first pulse width modulated (PWM) signals (PWM-Va1, PWM-Vb1, PWM-Vc1) based on received voltage commands (Va1, Vb1, Vc1) to render a first common mode signal (Vcm1) and also control the second switching elements (412, 512) to generate second PWM signals (PWM-Va2, PWM-Vb2, PWM-Vc2) based on received voltage commands (Va2, Vb2, Vc2) to render a second common mode signal (Vcm2). The rendered first and second common mode signals (Vcm1, Vcm2) have the same or similar waveform with opposite polarity with respect to one another.