Resonant Exciter Inverter Control for Stable Electric Machine Voltage
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Solution Overview
Problem
Conventional wound field synchronous electric machines are incapable of operating as both a starter motor and a generator, and they face challenges with DC power fluctuations causing ripples in AC power, leading to instability in output voltage, which is exacerbated by the need for large and heavy inductor and capacitor filter components in aircraft electrical systems.
Innovation Solution
A method of controlling a DC-AC inverter in an electric machine with a resonant main exciter and rotary transformer, where the frequency of AC power is adjusted based on DC power voltage levels to mitigate ripples and stabilize output voltage, potentially eliminating the need for large filter components by leveraging resonance gain effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional wound field synchronous electric machines are used, then they can operate as generators, but they cannot operate as starter motors when rotor speed is zero
Solution Approach 1:
The patent changes the excitation mode from conventional wound field to resonant excitation with a resonant main exciter. This parameter change enables the electric machine to operate as both a starter motor and generator, overcoming the limitation of conventional machines that cannot operate at zero rotor speed.
Solution Approach 2:
The patent designs the electric machine with a resonant main exciter that provides universal operation capability, allowing the same machine to function both as a starter motor during engine starting and as a generator during normal operation, eliminating the need for separate excitation systems.
2Stability of the object's composition
If DC power voltage level fluctuates, then the AC power output contains ripples, but using large inductor and capacitor filter components increases system weight
Solution Approach 1:
The patent converts the harmful effect of DC power fluctuations into a beneficial control signal. By detecting voltage level changes and using them to dynamically adjust the AC power frequency, the system transforms voltage instability into a control parameter that maintains output stability without requiring heavy filter components.
Solution Approach 2:
The patent implements dynamic frequency adjustment where the AC power frequency is continuously varied based on real-time DC voltage level detection. This dynamic control approach replaces static heavy filtering with active frequency modulation, reducing component weight while maintaining stability.
3Stability of the object's composition
If the frequency of AC power is adjusted dynamically based on DC voltage levels, then output voltage stability is improved, but control system complexity increases
Solution Approach 1:
The patent implements a feedback control mechanism where the DC voltage level is continuously monitored and used to adjust the AC power frequency. This closed-loop feedback system automatically maintains output voltage stability without requiring complex control algorithms or additional 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 approach stabilizes the output voltage of the electric machine while reducing the size and weight of filter components and lowering RF electromagnetic emissions, conforming to aviation RF emission limits and enabling efficient operation as both a starter motor and generator.
Implementation Method 1
a resonant main exciter having rotary transformer
Implementation Method 2
resonant main exciter having rotary transformer
Data Source
AI summary
Controlling a DC-AC inverter of an electric machine, where the electric machine comprises a resonant main exciter having rotary transformer. A voltage level of DC power received at a DC-AC inverter is monitored and the frequency of AC power generated by the DC-AC inverter and supplied to the rotary transformer is controlled based at least in part on the voltage level of the DC power.