Patent Application
20130154351
This application relates to an electric architecture that optimizes the control of the supply of power from a generator to an electrical bus.
Aircraft are typically provided with gas turbine engines. The gas turbine engines power the aircraft, but are also provided with generators that generate electricity as the gas turbine engine is driven.
Electricity is supplied to buses on the aircraft from the generators. Electrical components on the aircraft draw power from those buses. The supply of power from the generator to the bus must be capable of addressing overload conditions, in addition to normal steady state load demands.
Presently, the generator is connected to the bus with a conventional power switching device that acts as a circuit breaker. These conventional power switching devices are generally mechanical, and require a relatively long period of time to open.
The generator must be sized for addressing not just steady state load demands, but it must also be capable of meeting fault clearing conditions. When there is a fault, the generator must supply sufficient power such that the other components within the overall architecture still do receive power, even given the fault.
As such, the generator is undesirably large. In addition, other associated components, such as switches, wires, etc., are also made larger to handle the larger potential fault clearing power supply conditions.
So-called solid state switching devices are known, but typically have not been utilized for connecting a generator to the bus. Rather, they have only been utilized at the location of various small loads. Such electrical architecture has typically acted much like the prior art mechanical circuit breakers in that they wait until a high limit is crossed to open. This may require seconds, and thus does require the generator and associated components to be undesirably large as mentioned.
An electrical architecture includes at least one generator. A fast switching device connects the generator to a bus. A plurality of loads draw electrical power from the bus.
These and other features of this application will be better understood from the following specification and drawings, the following of which is a brief description:
The buses 24 are shown connected to loads 28, and through switches 30. The switches may act as circuit breakers, and disconnect the load from the bus 24 under certain conditions, as known.
Another circuit breaker or switch 30 connects the main bus 24 to a non-essential bus 32. The non-essential bus 32 may power various systems that are not essential to continued operation of the aircraft. Another switch 30 connects the non-essential bus 32 to a load 34. In practice, there would typically be many more loads connected to both buses 24 and 32.
As shown, a switch 40 connects the generator 22 to the bus 24. This function has conventionally been provided by a mechanical switch.
However, in the present invention, the switches 40 are fast switching devices. One such fast switching device may be a solid state switching device. A second such fast switching device could be a hybrid incorporating features of both solid state and mechanical. Such switching devices may open and close at an AC wave form zero crossing. This reduces the fault current to zero. For this reason, the switches 40 are only influenced by the steady state power and a load startup inrush current, and not by the AC fault current.
In addition, such switches can transition to open or closed states in an extremely short period of time. As an example, it is possible for such switches to transition in less than one millisecond. Switches 30, and cross-tie switching devices 26 may also be solid state switching devices.
In the new architecture, a control 100 for the overall system may receive signals from the switches 26, 30, and 40. Each of the distinct locations have distinct expected profiles that the switches may experience. This may relate to a current, to a change in current, to a voltage, or to any number of other electrical features. That is, each of the locations, dependent on the loads they are powering, or the buses they are supplying, would have an expected signal profile. The control 100 is provided with the expected profile, and also a series of conditions that would likely exist at that location for that switch in the event of an upcoming fault. The control 100 is thus operable to compare received signals with expected profiles and immediately open the particular switch associated with the fault should the two signals differ by more than a predetermined amount.
Once this occurs, the generators need not supply unduly high power, and much smaller generators 22 may be incorporated into the architecture. Similarly, the switches, wires, etc. may all be made smaller as none of them will be required to handle the overcurrents as are currently found in the prior art.
The above features enable the generator and its associated distribution components to be sized according to the steady state and load inrush current, instead of a fault clearing condition. As an example, it is anticipated that a generator with the inventive architecture could be 15-25% the size of a generator used in comparable prior art electric architectures. Further, the wiring, cross tie devices, and other load protection systems can also all be made correspondingly smaller.
Although an embodiment of this invention has been disclosed, a worker of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
