Common-Mode Filter for Delta-Wound Synchronous Machine Currents

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Solution Overview

Problem

Rotating electrical machines with Delta-connected stator windings experience circulation currents due to additive third harmonic voltages, leading to torque ripple, reduced output torque, and efficiency loss.

Innovation Solution

Implementing a common mode filter with magnetic core and filter windings serially connected to Delta-connected stator windings to suppress circulation currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If Delta connection is used for stator windings, then power output and efficiency are improved, but circulation current is generated causing torque ripple and losses

Engineering Contradiction:

Improvepower outputVSAvoidcirculation current

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

A common mode filter is introduced as an intermediary component between the power source and the Delta-connected stator windings. The filter includes a magnetic core with filter windings wound around it, and capacitors connected to suppress the circulation current generated by the Delta connection, thereby eliminating the harmful effect while preserving the power output benefits

Inventive Principle:

Principle #24Intermediary (Mediator)

2Force

If Delta connection is used for stator windings, then torque output is improved, but torque ripple increases due to circulation current

Engineering Contradiction:

Improvetorque outputVSAvoidtorque ripple

Core Design Contradiction:

ForceVSStability of the object's composition

Solution Approach 1:

The common mode filter acts as a mediator that suppresses the circulation current responsible for torque ripple. The filter windings are serially connected to the stator windings and wrapped around the magnetic core, creating a filtering effect that smooths out the torque fluctuations while maintaining the overall torque output

Inventive Principle:

Principle #24Intermediary (Mediator)

3Use of energy by moving object

If Delta connection is used for stator windings, then electrical efficiency is improved, but copper loss increases due to circulation current

Engineering Contradiction:

Improveelectrical efficiencyVSAvoidcopper loss

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The common mode filter with its magnetic core and filter windings serves as an intermediary that reduces the circulation current flowing through the stator windings. By suppressing this parasitic current, the filter reduces copper losses in the windings while preserving the electrical efficiency benefits of the Delta connection

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Reduces circulation currents by 60%, increases torque output by 6%, and decreases copper loss by 20%.

Implementation Method 1

a common mode filter, including a magnetic core positioned adjacent to an exterior surface of the stator, wherein filter windings from the common mode filter are circumferentially wound around the magnetic core and are serial connected to the plurality of stator windings

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS12592615B2Filter to suppress current circulation in rotating electrical machine

Publication Date: 2026.03.31 BORGWARNER INC

AI summary

A three-phase alternating current (AC) synchronous machine including a stator having a plurality of stator slots; a plurality of stator windings arranged in a Delta connection and received within the stator slots; and a common mode filter included with the stator, wherein filter windings from the common mode filter are circumferentially wound around a magnetic core of the common mode filter and are serial connected to the stator windings.