Turbomachine Starter-Generator Damping Bars Starting Torque
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Solution Overview
Problem
Existing turbomachine starter-generators face challenges in providing sufficient starting torque, especially in high-power applications, due to increased mass and bulk from modified exciters and require controllable switches that are disabling elements, and operation in asynchronous mode is degraded compared to synchronous mode.
Innovation Solution
A turbomachine starter-generator with angularly distributed damping bars promoting asynchronous motor operation without short-circuiting the rotor field, coupled with an angular position sensor and start-up regulator circuit to control torque, allowing efficient switching to synchronous mode when necessary, and an inverter control system to manage starting torque based on rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the exciter is modified to operate in rotating transformer mode to supply excitation current at start-up, then starting capability is improved, but mass and bulk increase
Solution Approach 1:
The invention extracts the starting torque function from the exciter by using damping bars in the rotor inductor of the main electrical machine. The exciter is taken out of the starting function and dedicated solely to excitation, while the damping bars provide the starting torque capability without modifying the exciter structure.
Solution Approach 2:
The damping bars in the rotor inductor serve multiple functions: they provide starting torque in asynchronous motor mode during start-up, and maintain synchronous motor mode operation during normal operation. This multi-functionality eliminates the need for separate starting mechanisms and reduces overall system mass.
2Power
If controllable switches are inserted in parallel or series with the rotor inductor to enable asynchronous starting, then starting capability is improved, but device complexity increases
Solution Approach 1:
The damping bars automatically provide the necessary starting torque function without requiring external control switches. The system self-regulates by utilizing the inherent properties of the damping bars in asynchronous motor mode during start-up, eliminating the need for complex switching mechanisms.
3Power
If operation in asynchronous mode is used to provide starting torque, then starting capability is improved, but operational performance is degraded compared to synchronous mode
Solution Approach 1:
The system dynamically transitions from asynchronous motor mode during start-up to synchronous motor mode during normal operation. The damping bars enable asynchronous operation only when needed for starting, while the main electrical machine operates in the more efficient synchronous mode during production, optimizing both starting capability and operational productivity.
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 configuration ensures high starting torque with reduced mass and bulk, avoids torque ripples, and maintains efficient operation by optimizing asynchronous mode performance while enabling seamless transitions to synchronous mode as needed, ensuring reliable high-power startup.
Implementation Method 1
damping bars which promote operation as an asynchronous motor
Implementation Method 2
angular position sensor connected to the second start-up regulator circuit to supply the latter with information representative of the angular position of the rotor
Implementation Method 3
inverter control system to manage starting torque based on rotational speed
Implementation Method 4
operate the main electric machine in synchronous electric motor mode by supplying its stator windings with an alternating voltage
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A turbine engine starter/generator includes a main electrical machine (20), having a stator and a rotor (22) having a wound rotor inductor and shock-absorbing bars forming a housing, and an exciter (30), having a stator inductor and a rotor having rotor windings connected to the rotor inductor of the main electrical machine via a rotating rectifier (36). During a first step of the starting phase, the main electrical machine (20) is controlled, in asynchronous motor mode, by means of injecting an alternating current into the stator windings thereof, a starting torque being created by means of the single shock-absorbing bars without any particular contribution by the rotor inductor of the main electrical machine to the generation of the starting torque. During a second step following the starting phase, the main electrical machine (20) is controlled, in synchronous motor mode, by means of injecting an alternating current into the stator windings thereof while supplying continuous current to the rotor inductor of the main electrical machine via the exciter (30), the transition from the first step to the second step of the starting phase being controlled when the rotation speed of the shaft reaches a predetermined value.