Starter-Generator Rotor Position Sensing Using Auxiliary PMG
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Solution Overview
Problem
The operation of a wound field synchronous dynamoelectric machine (WFSDM) as a starter motor for aeronautical gas turbine engines requires accurate rotor position sensing, which is typically achieved using an electromechanical shaft position resolver, adding cost, complexity, and unreliability, while existing 'sensorless' control strategies are not robust enough.
Innovation Solution
The integral auxiliary permanent magnet generator (PMG) is used as an angular position sensor in the starting mode of the WFSDM, combining its output with modified power electronic technology to create a simple and robust motor drive architecture that eliminates the need for a dedicated resolver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an electromechanical shaft position resolver is used for rotor position sensing, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent reuses the PMG (permanent magnet generator) that already exists in the WFSDM for generating electrical power, giving it a dual function: it simultaneously provides rotor position sensing information during motor operation. This eliminates the need for a separate dedicated position sensor, reducing device complexity while maintaining measurement precision through the PMG's inherent back-EMF signals.
Solution Approach 2:
The system uses its own integral PMG to provide position sensing information without requiring external dedicated sensors. The PMG's output signals are processed to extract rotor position data, allowing the system to sense its own state using existing components, thereby reducing overall system complexity and cost.
2Measurement precision
If an electromechanical shaft position resolver is used for rotor position sensing, then measurement precision is improved, but reliability deteriorates
Solution Approach 1:
By making the PMG serve dual purposes (power generation and position sensing), the patent eliminates additional electromechanical components that could fail. The position sensing function is derived from the PMG's electrical outputs without requiring separate sensing hardware, thereby improving reliability by reducing the number of potential failure points.
Solution Approach 2:
The patent extracts the position sensing information directly from the PMG's output signals through signal processing, removing the need for separate position sensing hardware. This extraction approach eliminates the reliability issues associated with additional electromechanical sensors and their wiring.
3Device complexity
If sensorless control strategies are used to eliminate position sensors, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The system uses its own PMG output signals to provide accurate position information, avoiding the need for external sensors while maintaining precision. The PMG's back-EMF signals contain sufficient information for accurate rotor position detection, and the signal processing techniques extract this information reliably without the complexity of dedicated sensing hardware.
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
This solution provides a reliable and cost-effective means to control rotor position and torque during starting, enhancing the WFSDM's suitability as a starter-generator for aeronautical applications by leveraging the PMG's ability to provide rotor position information independently, thus reducing system complexity and improving reliability.
Implementation Method 1
an integral auxiliary permanent magnet generator (PMG) is used as an angular position sensor in the starting mode of the WFSDM
Implementation Method 2
a scaling amplifier for receiving a signal derived from a polyphase output signal generated by the PMG and amplifying it by an amplification factor K to generate a scaling amplifier output signal that approximates back electromotive force (EMF) potentials
Implementation Method 3
a Clarke transformation that receives the scaling amplifier output signal and converts it to a Clarke transformation output signal that comprises two orthogonal electrical potentials Vx and Vy representing direct and quadrature axis electrical potentials
Implementation Method 4
an inverter for receiving the gate drive signal and generating motor drive output signals for each respective phase of the WFSDM that are suitable for driving the WFSDM with the desired rotational speed and torque
Data Source
AI summary
A motor control system for a wound field synchronous dynamoelectric machine used as an electrical starter and a generator for aeronautical engines that uses its integral auxiliary permanent magnet generator as an angular position sensor in its starting mode.