Electromagnetic Circuit Interrupter for High Voltage DC Aircraft Power Systems
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Solution Overview
Problem
High voltage DC electromagnetic switches in aircraft power distribution systems face reduced component lifetime due to arcing, which conventional techniques have not adequately addressed for safety-critical applications.
Innovation Solution
An electromagnetic circuit interrupter that sustains an arc for a predetermined time before fully opening the contacts, allowing for the dissipation of inductive energy and minimizing contact sputtering, with the first predetermined distance being less than the second to control temperature rise below the melting point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional electromagnetic switches are used to interrupt high voltage DC circuits, then the switching speed is fast (microseconds), but the contact lifetime is reduced due to arcing and contact sputtering
Solution Approach 1:
The contact opening process is segmented into two distinct phases: first, the contacts are separated by a first predetermined distance to sustain an arc and dissipate inductive energy; second, after a predetermined time, the contacts are separated by a second predetermined distance to extinguish the arc and break the circuit. This segmentation allows the switching function to be divided into energy dissipation and circuit interruption, resolving the contradiction between fast switching and contact protection.
Solution Approach 2:
The arc is sustained for a predetermined time period before the contacts are fully opened. This preliminary action allows the inductive energy to be dissipated through the arc before the contacts reach temperatures that would cause melting and sputtering, thereby extending contact lifetime while maintaining effective circuit interruption.
2Productivity
If the contacts are opened widely and quickly to break the circuit, then the circuit interruption is fast, but the inductive energy causes the contacts to become hot enough to melt and sputter
Solution Approach 1:
The harmful inductive energy that normally causes contact overheating and sputtering is converted into a beneficial arc that sustains for a predetermined time. This arc serves as a controlled energy dissipation path, allowing the inductive energy to be released gradually through the arc rather than directly heating the contacts, thus protecting them from thermal damage.
Solution Approach 2:
The contacts are held at a first predetermined distance for a predetermined time to allow the arc to dissipate inductive energy before the contacts are fully separated. This preliminary energy dissipation action prevents the contacts from reaching melting temperatures, eliminating the harmful thermal effects while maintaining circuit interruption functionality.
3Reliability
If additional circuitry is added to dissipate inductive energy, then the contact lifetime is enhanced, but the device complexity increases
Solution Approach 1:
The electromagnetic switch contacts serve multiple functions: they act as both the switching element and the arc electrode for energy dissipation. The same contacts that open to interrupt the circuit also sustain the arc that dissipates inductive energy, eliminating the need for separate energy dissipation circuitry and maintaining device simplicity while extending contact lifetime.
Solution Approach 2:
The circuit interrupter uses its own contacts to dissipate the inductive energy through a controlled arc, rather than requiring external circuitry. The contacts themselves serve the dual purpose of switching and energy dissipation, making the system self-sufficient and avoiding additional components that would increase complexity.
4Reliability
If the contacts are held at a small separation distance for a long time to dissipate energy, then contact sputtering is minimized, but the total switching time increases
Solution Approach 1:
The switching process is segmented into two phases with different priorities: first, a controlled arc sustains phase where contacts remain at a small distance to dissipate energy and protect against sputtering; second, a rapid opening phase where contacts are quickly separated to complete circuit interruption. This segmentation allows optimization of each phase for its specific function, minimizing overall switching time while protecting contact durability.
Solution Approach 2:
After the predetermined energy dissipation time, the contacts are rapidly separated by a second predetermined distance to quickly extinguish the arc and complete the circuit interruption. This rushing through the final separation phase minimizes the time the contacts are in a vulnerable state, reducing total switching time while maintaining contact protection during the critical energy dissipation period.
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 significantly enhances the operational lifetime and reliability of the contacts by dissipating inductive energy before the contacts become hot enough to melt, reducing contact sputtering and arc restrike.
Implementation Method 1
separate first and second electrical contacts by a first predetermined distance for a predetermined time so as to sustain an arc when the contact mechanism is opened
Implementation Method 2
dissipate the inductive energy stored in the circuit so as to minimise the energy dissipated in the electromagnetic switches themselves
Implementation Method 3
separate the first and second electrical contacts by a second predetermined distance after the predetermined time so as to extinguish the arc
Data Source
AI summary
In one aspect, the present invention provides an electromagnetic circuit interrupter for use in a high voltage direct current (DC) aircraft power distribution system. The electromagnetic circuit interrupter comprises a contact mechanism operable to separate first and second electrical contacts by a first predetermined distance d1 for a predetermined time τ so as to sustain an arc when the contact mechanism is opened. The contact mechanism is further operable to separate the first and second electrical contacts by a second predetermined distance d2 after the predetermined time τ so as to extinguish the arc. The first predetermined distance d1 is less than said second predetermined distance d2. By deliberately sustaining the arc for a relatively long period of time, this aspect of the present invention is particularly useful for extending the operational lifetime of the contacts and thereby of the electromagnetic circuit interrupter itself.