Patent Application
20090200864
This disclosure relates to bus bar switching devices used in high current aircraft power distribution systems.
In typical primary (or high current) aircraft electrical power distribution systems, the power is fed to the distribution boxes/panels by heavy gauge wires. These wires are bolted onto a terminal block, which connects to the box internal bus bars. The bus bars are typically heavy aluminum or copper strips that are formed to a desired shape for easy installation and smallest space consumption. The bus bars also must be segregated from one another.
Electromechanical contactors including diagnostics and protection functions (sometimes referred to as “smart contactors”) toe-switch the power provided by these bus bars between one another. The electromechanical contactors are bolted onto the bus bars at their input terminals. The output terminals of the electromechanical contactors are bolted to the next bus bar dedicated for the output of the power.
The electromechanical contactors are large, heavy and costly. They wear out, requiring replacement, which can be difficult when located in spaces difficult to access. What is needed is a power distribution system and switching device that is light, cost effective and capable of handling high currents.
A bus bar assembly for a power distribution system is disclosed that includes first and second bus bars electrically isolated from one another. The bus bars are interconnected by a semiconductor switching element that is mounted on at least one of the first and second bus bars. A driver logic control device is in communication with the semiconductor switching element. The driver logic control device is configured to electrically connect the first and second bus bars in response to a command to provide power to an aircraft component, such as a secondary power distribution box.
These and other features of the application can be best understood from the following specification and drawings, the following of which is a brief description.
An aircraft power distribution system 11 is shown in
The mechanical contactors typically used between the first and second bus bars 15, 17 are replaced with a semiconductor switching element 20. In one example, power MOSFETs 38 are used, as schematically shown in
The semiconductor switching element 20 is assembled into a package that can be electrically connected to the first and second bus bars 15, 17. For example, one type of package is SMT style, which can be assembled onto a PCB. The PCB can then be mounted onto or plugged into the bus bars 16. For improved weight and volume reduction in aircraft applications, bare dies could be assembled directly onto the PCB. However, for high current applications it is difficult to feed the current through a connector from the bus bars 16 to the PCB and it is also difficult to manage this current within the PCB due to the needed high copper content. In general, the copper and connector losses on the PCB cause a significant cooling challenge.
Rather than placing the bare pins on a dedicated PCB or module that plugs into one of the bus bars 16, the bare dies 24 are attached directly onto the first bus bar 15, for example. In this manner, losses from the connections associated with such a PCB arrangement can be eliminated. The dies 24 can be attached using solder 25 (
Returning to
A driver logic control device 36 communicates with the semiconductor switching element 20. The driver logic control device 36 drives the dies 24 to electrically connect the first and second bus bars 15, 17 to one another in response to a command 46. In one example, the semiconductor switching element 20 and the driver logic control device 36 are both located within the power distribution box 10 but at locations 32, 34 that are remote from one another. In this manner, the driver logic control device 36 can be positioned in a more accessible location than the semiconductor switching element 20.
Although example embodiments have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.
