Aircraft Valve Switch Wetting Current Circuit
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Solution Overview
Problem
Electromechanical switches in aircraft environmental control systems face reliability issues due to film resistance on electrical contacts, which can prevent current flow when the contacts alternate between dry and moist conditions, and existing currents are often insufficient to break through oxidation or contamination.
Innovation Solution
An analog to digital converter circuit provides additional wetting current to the switch contacts when they close, combining it with a current from a processing circuit to ensure the combined current exceeds the minimum required to break through film resistance, thereby improving switch reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional wetting current is provided to break through film resistance, then switch reliability is improved, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary component (analog-to-digital converter circuit) that provides additional wetting current to the switch contacts. This intermediary circuit acts as a mediator between the existing current source and the switch, adding the necessary current boost to break through film resistance without requiring a complete redesign of the power supply system.
Solution Approach 2:
The patent applies preliminary action by providing the additional wetting current in advance, specifically at the moment when switch contacts close. The analog-to-digital converter circuit is configured to detect the closing event and immediately supply the extra current needed to overcome film resistance before it can prevent proper contact operation.
2Device complexity
If existing current is used without modification, then device complexity is minimized, but switch reliability deteriorates due to insufficient current to break through oxidation and contamination
Solution Approach 1:
The patent changes the current parameter by introducing an additional current source that supplements the existing current. The analog-to-digital converter circuit modifies the current delivery by adding a boosting component that increases the total current flowing through the switch contacts, enabling them to overcome oxidation and contamination without changing the fundamental current supply architecture.
3Reliability
If wetting current is increased to ensure current flow through contacts, then switch operation reliability is improved, but energy consumption increases
Solution Approach 1:
The patent applies periodic action by providing the additional wetting current only at specific moments when the switch contacts close, rather than continuously. The analog-to-digital converter circuit detects the closing event and triggers the current boost temporarily, reducing overall energy consumption compared to maintaining a continuously elevated current level.
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 increased wetting current ensures reliable operation of valve position switches by ensuring current flow through the contacts, even when film resistance is present, enhancing the overall performance of aircraft environmental control systems.
Implementation Method 1
The techniques of this disclosure provide additional wetting current at the time the switch contacts close to improve reliability of the valve position switches
Data Source
AI summary
This disclosure describes techniques for increasing wetting current for an electromechanical switch. In one example application, an aircraft may include one or more valves used to control the temperature of aircraft interior. The valves may include one or more valve position switches to indicate certain valve positions, e.g. fully open, fully closed, fifty percent open, and so on. In some examples, the valve position switches may receive current at electromechanical contacts of the switch that is less than the wetting current. The techniques of this disclosure provide additional wetting current at the time the switch contacts close to improve reliability of the valve position switches. In some examples, an analog to digital converter circuit may be configured to provide the additional wetting current to the switch.