DC Essential Bus Switching for Backfeed Blocking and Float Charging
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Solution Overview
Problem
Conventional DC essential bus systems in aircraft face challenges in maintaining power to critical systems during generator failures, as they often require manual reconfiguration or additional components like diodes that can prevent float charging of batteries or require separate chargers, and lack sufficient space for AC relays.
Innovation Solution
The implementation of a controller that selectively engages a diode bypass contactor between the DC essential bus and the DC electric power source, allowing for automatic switching between primary and alternate power sources while preventing backfeeding and enabling float charging, using a diode-diode bypass arrangement or a contactor-diode configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode is used between the DC essential bus and the DC electric power source, then backfeeding is prevented, but float charging of batteries is blocked and separate chargers are required
Solution Approach 1:
The patent employs a dynamically controllable contactor instead of a static diode to control the electrical connection between the DC essential bus and DC electric power source. The contactor can be selectively engaged or disengaged based on operational conditions, allowing the system to adapt between preventing backfeeding and enabling float charging modes, thereby eliminating the need for separate chargers while maintaining reliability
2Extent of automation
If AC relays are added to the system for automatic switching, then automatic power source switching is achieved, but available space is insufficient
Solution Approach 1:
The patent replaces mechanical AC relays with solid-state electronic switching components controlled by a controller. This substitution eliminates the need for large mechanical relay devices while achieving automatic switching functionality through electronic control signals, thereby resolving the space constraint while maintaining automation capability
Solution Approach 2:
The controller serves multiple functions: it monitors the operational state of power sources, controls the engagement of contactors, manages the switching between primary and alternate power sources, and coordinates the overall power distribution. This multi-functional approach consolidates what would otherwise require multiple separate components into a single integrated control unit, saving valuable space
3Device complexity
If manual reconfiguration is required during generator failures, then system complexity is reduced, but crew workload increases and response time is delayed
Solution Approach 1:
The system implements self-service automation where the controller automatically detects generator failures, determines the appropriate power source configuration, and executes the switching operations without requiring manual intervention from the crew. This self-acting capability maintains relative system simplicity while eliminating the time loss associated with manual reconfiguration during emergencies
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
Ensures reliable power to critical aircraft systems by automatically switching between power sources, preventing isolation of the DC essential bus and allowing for float charging of batteries, thus enhancing safety and reducing crew workload during emergencies.
Implementation Method 1
selectively engage the contactor to enable a diode bypass disposed between a direct current (DC) essential bus and a DC electric power source during a first state of operation and to selectively engage the contactor to enable a diode disposed between the DC essential bus and the DC electric power source during a second state of operation
Data Source
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AI summary
Examples described herein provide an electric power distribution system (EPDS) that includes a transformer rectifier unit (TRU) (107, 108, 109) that receives alternating current (AC) electric power from an AC electric power source (104, 105, 106) during a first state of operation. The EPDS further includes a direct current (DC) electric power source (110) that receives the DC electric power from the TRU during the first state of operation. The EPDS further includes a DC essential bus (112) that receives the DC electric power from the DC electric power source during the first state of operation and that receives the DC electric power from another source during a second state of operation. The EPDS further includes a controller (127, 128, 129) to selectively engage a diode bypass contactor to enable a diode during the second state of operation, and selectively engage the diode bypass contactor (243) to enable a diode bypass (241) during the first state of operation.