Sensorless Re-engagement of AC Synchronous Machine
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Solution Overview
Problem
Current sensorless control systems for AC synchronous dynamoelectric machines face challenges in accurately determining rotor position and velocity at low speeds, particularly below 10% of normal operating speed, making it difficult to deliver continuous and smooth starting torque, and lack a practical method for re-engagement at non-zero speeds.
Innovation Solution
A method for starting a gas turbine engine using a synchronous multiphase AC dynamoelectric machine that allows re-engagement at non-zero rotor speeds by applying electrical excitation, measuring EMF, determining rotor speed and position using sensorless means, and transitioning between open-loop and closed-loop control algorithms based on predetermined speed and acceleration thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If open-loop control is used for starting at zero speed, then ease of operation is improved, but reliability deteriorates when re-engagement is needed at non-zero speeds
Solution Approach 1:
The system implements dynamic mode switching capability that allows transition from open-loop control to closed-loop sensorless control based on real-time rotor speed measurement. This enables the system to handle both zero-speed starting (using open-loop for ease of operation) and non-zero-speed re-engagement (using closed-loop for reliability), resolving the contradiction between operational simplicity and re-engagement reliability
Solution Approach 2:
The control system achieves multi-functionality by incorporating both open-loop and closed-loop sensorless control capabilities within a single unified control architecture. This universal control system can operate effectively across the entire speed range from zero to full operating speed, providing both the ease of zero-speed starting and the reliability of non-zero-speed re-engagement
2Reliability
If a separate air turbine or DC dynamoelectric machine is used as starter, then reliability is improved, but weight and device complexity increase
Solution Approach 1:
The AC synchronous dynamoelectric machine is designed to perform dual functions: serving as both the generator for normal operation and the starter dynamoelectric machine for starting operations. This eliminates the need for separate starter machines (air turbine or DC dynamoelectric machine) and their associated mechanical clutch mechanisms, significantly reducing weight and device complexity while maintaining reliability through the sophisticated open-loop to closed-loop control transition
Solution Approach 2:
The invention merges the generator and starter functions into a single AC synchronous dynamoelectric machine. By integrating both functions into one machine and配合 with the dual-mode control system, the design eliminates the need for separate starter components and mechanical clutch mechanisms, achieving weight and complexity reduction while preserving the reliability benefits of dedicated starter systems
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 reliable and smooth starting torque across the entire speed range, including non-zero speeds, without additional hardware, by accurately determining rotor position and velocity, and ensuring safe and efficient re-engagement of the starting process.
Implementation Method 1
measuring electromotive force (EMF) generated in the stator
Data Source
Figure 1~2
Figure 3
AI summary
A method of starting a gas turbine engine with a synchronous multiphase alternating current (AC) dynamoelectric machine with a rotor and a stator that allows re-engagement of a starting operation at non-zero rotor speeds comprises the steps of: applying electrical excitation to the rotor; measuring electromotive force (EMF) generated in the stator; determining rotor speed, acceleration and position from the measured EMF by sensorless means; initiating closed-loop sensorless position controlled power to the stator if the determined rotor speed is at least a pre-determined minimum closed-loop sensorless re-engagement speed; initiating open-loop position controlled power to the stator if the determined rotor speed is less than the pre-determined minimum closed-loop sensorless re-engagement speed but at least a predetermined minimum open-loop re-engagement speed and the determined rotor acceleration is no more than a pre-determined maximum open-loop re-engagement acceleration; and initiating open-loop zero-speed start power to the stator if the determined rotor speed is less than the predetermined minimum open-loop re-engagement speed.