Brushless Starter Generator Damper Bars for Current Limiting
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Solution Overview
Problem
High power brushless wound field starter generators require low stator winding inductance to meet transient power quality requirements, leading to high peak phase currents during start mode, which reduces overall system performance and torque capability.
Innovation Solution
Incorporating paramagnetic or soft ferromagnetic damper bars that fill the slot openings in the rotor, increasing rotor sub-transient direct-axis inductance and reducing peak winding phase currents without affecting steady-state performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low stator winding inductance is used to meet transient power quality requirements, then power quality is improved, but peak phase currents during start mode increase
Solution Approach 1:
The patent introduces an intermediary element (external inductor or feeder cable with higher inductance) between the inverter and the stator winding to limit peak phase currents. This intermediary component absorbs the harmful current spikes during start mode while allowing the stator winding to maintain low inductance for good transient power quality during generate mode.
Solution Approach 2:
The patent changes the inductance parameter by adding external inductance through an external inductor or high-inductance feeder cables. This parameter change allows the system to have low stator winding inductance for power quality while compensating with external inductance to limit peak currents during start mode operations.
2Object-generated harmful factors
If current carrying capability of semiconductor switches is increased to handle high peak currents, then start mode current capability is improved, but system weight increases
Solution Approach 1:
The external inductor acts as a mediator that limits peak currents, allowing the use of smaller, lighter semiconductor switches with lower current carrying capability while still protecting the system during start mode operations.
3Object-generated harmful factors
If armature leakage inductance is increased to reduce peak currents, then peak phase currents are reduced, but steady-state generate mode performance is impacted
Solution Approach 1:
The patent segments the inductance function into two parts: low stator winding inductance for steady-state generate mode performance and external inductance for limiting peak currents during start mode. This segmentation allows each part to optimize for its specific function without compromising the other.
Solution Approach 2:
The system dynamically utilizes different inductance characteristics at different operating modes: the external inductor provides current limiting during transient start mode while the low stator winding inductance maintains optimal performance during steady-state generate mode operations.
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
The solution effectively mitigates high peak winding phase currents during start mode operations, enhancing power capability and density of the starter generator while maintaining steady-state performance.
Implementation Method 1
Incorporating paramagnetic or soft ferromagnetic damper bars that fill the slot openings in the rotor, increasing rotor sub-transient direct-axis inductance
Data Source
AI summary
A brushless starter generator includes a wound field generator having a rotor that includes a damper winding, wherein the damper winding includes a plurality of poles. Also included is at least one pole face disposed within each of the plurality of poles, wherein the at least one pole face comprises a slot opening. Further included is at least one damper bar relatively entirely filling the slot opening.