WRSM Rotor Current Sensing via Hall Detection at the Shaft Winding

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Solution Overview

Problem

Existing systems for wound rotor synchronous machines (WRSMs) lack direct measurement of rotor current, relying on estimates from primary and secondary transformer coils, leading to inaccuracies in current control.

Innovation Solution

Implementing a rotary transformer with a primary and secondary coil, a rotor connected to the secondary coil outputs, and a winding around the shaft, using a contactless Hall effect sensor to directly measure the magnetic field of the winding for accurate rotor current detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If rotor current is measured directly using a sensor inside the rotor, then measurement precision is improved, but device complexity and safety risks increase due to contactless requirements

Engineering Contradiction:

Improverotor current measurement precisionVSAvoidsensor system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent uses the magnetic field as an intermediary to transmit rotor current information from the rotating rotor to the stationary sensor. The Hall effect sensor detects the magnetic field generated by the rotor current through the stationary winding, enabling contactless measurement while maintaining measurement precision and avoiding the complexities of in-rotor sensor installation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If rotor current is estimated using transformer coil currents, then device complexity is reduced, but measurement precision deteriorates due to indirect estimation

Engineering Contradiction:

Improvemeasurement system complexityVSAvoidrotor current measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces the electrical measurement approach (measuring transformer coil currents) with a magnetic field-based measurement approach. By using a Hall effect sensor to directly detect the magnetic field generated by rotor current, the system achieves higher measurement precision while keeping the overall device complexity manageable through contactless sensing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Enables precise measurement of rotor current, minimizing estimation errors and improving control accuracy by directly measuring the magnetic field generated by the rotor current.

Implementation Method 1

measuring a magnetic field of a winding using a contactless Hall effect sensor

Methodology Applied

Scientific EffectHall effect: Hall Effect

Data Source

PatentUS20260016508A1Direct rotor current measurement for transformer-fed wound rotor machine

Publication Date: 2026.01.15 BORGWARNER INC

AI summary

A wound rotor synchronous machine (WRSM) includes a rotary transformer. The rotary transformer has a primary coil and a secondary coil. A rotor is connected to a positive direct current (DC) output of the secondary coil and connected to a negative DC output of the secondary coil. The rotor includes a shaft. A winding is wound around the shaft. The winding includes a turn of one of the positive DC output and the negative DC output. A contactless sensor is disposed adjacent the winding and in communication with a controller.