Generator With Parallel AC Accessory Bus For Weight Reduction
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Solution Overview
Problem
Existing aircraft electrical systems face challenges in efficiently distributing AC power to engine accessories without the need for heavy shielding, and in preventing power drainage during short circuits on the DC bus, which can disrupt critical motor operations.
Innovation Solution
An electrical system that utilizes a high frequency AC accessory bus parallel to the DC bus, with a switch to isolate the AC and DC buses during short circuits and a battery-powered voltage regulator to maintain motor operation, eliminating the need for shielding and ensuring continuous power to critical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If AC power is distributed at high frequency (above 800 Hz) without shielding, then weight is reduced, but electromagnetic interference and power distribution reliability deteriorate
Solution Approach 1:
The patent introduces an AC bus as an intermediary power distribution path that operates in parallel with the traditional DC bus. The AC bus carries high-frequency AC power directly to accessories without requiring heavy shielding, while the DC bus continues to provide stable power to critical flight systems. This intermediary AC distribution path resolves the contradiction by enabling weight reduction through unshielded high-frequency AC transmission while maintaining reliability through the parallel DC bus architecture.
Solution Approach 2:
The electrical power distribution system is segmented into two independent parallel paths: an AC bus for non-critical accessories and a DC bus for critical flight systems. This segmentation allows each bus to be optimized for its specific function - the AC bus for lightweight high-frequency distribution and the DC bus for stable reliable power - thereby resolving the contradiction between weight reduction and reliability maintenance.
2Reliability
If a short circuit occurs on the DC bus, then power is drained from the system, but accessories on the AC bus continue to operate
Solution Approach 1:
The patent segments the power distribution into isolated AC and DC bus systems with independent switching control. When a short circuit is detected on the DC bus, the system can isolate the DC bus from the generator while maintaining AC bus operation. This segmentation prevents power drainage from affecting the entire system - the generator continues powering AC bus accessories while the DC bus short circuit is contained and isolated, resolving the contradiction between preventing power loss and maintaining accessory reliability.
Solution Approach 2:
The system incorporates monitoring and control mechanisms that detect short circuit conditions on the DC bus and provide feedback to switching devices. This feedback enables automatic isolation of the affected DC bus segment, preventing further power drainage while maintaining AC bus operation. The feedback control resolves the contradiction by dynamically responding to fault conditions to prevent energy loss while preserving accessory power supply.
3Device complexity
If the generator frequency is converted to DC, then power distribution simplicity is improved, but the ability to provide AC power to accessories is lost
Solution Approach 1:
The patent implements a dual-bus architecture where the generator can supply power in multiple forms - high-frequency AC to the AC bus and converted DC to the DC bus. This multi-functionality allows the same generator to serve both AC and DC power distribution needs simultaneously, resolving the contradiction between system simplicity and AC power capability. The system gains versatility without adding a separate AC generator, maintaining relative simplicity while enabling AC power supply to accessories.
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 reduces weight by eliminating the need for shielding and ensures reliable operation of flight-critical pumps by maintaining power to motors and regulators during short circuits, enhancing the reliability and efficiency of the electrical system.
Implementation Method 1
a generator to be driven as part of a gas turbine engine... Power generated by the generator flows to an aircraft bus
Implementation Method 2
proposed systems have used inverter/rectifiers to convert the AC power into DC
Implementation Method 3
a battery providing power to the voltage regulator when the switch is open, and providing power to the generator in a start mode
Implementation Method 4
a voltage regulator receiving a control voltage from the AC accessory bus... maintaining power to motors and regulators during short circuits
Data Source
Figure 1
AI summary
An aircraft electrical system includes a generator (28) that supplies electrical AC power to a plurality of accessories (38, 42, 46) associated with a gas turbine engine. The generator also supplies power to an aircraft DC bus (22) in parallel to the supply to the accessory bus.