Hybrid aircraft electrical architecture with both variabe and constant frequency generators

BACKGROUND OF THE INVENTION

0001This application relates to an electrical generation system for use in an aircraft environment.

0002Aircraft are typically provided with gas turbine engines, which include turbine rotors that rotate to provide power. Generators are associated with these gas turbine engines, and generate electricity from the rotation of a shaft driven by the turbine rotors. The electricity is utilized for various functions on the aircraft, including providing electric power to systems associated with the gas turbine engines, as well as providing electricity to other uses on the aircraft.

0003A gas turbine engine can rotate at varying speed. A simple generator driven by such an engine will generate a variable frequency.

0004It is known to provide a gas turbine engine with a pair of generators. In some cases, the generators have been variable frequency.

0005It is also known to provide a pair of constant frequency generators on a gas turbine engine. A constant frequency generator adapts to the engine's speed variation such that the generator still provides a constant speed and thus constant frequency output.

0006More recently, for several reasons, aircraft designers have wanted to utilize variable frequency generators. The use of the variable frequency generators raises some challenges, such as large, sustained, torsional oscillating loads in associated gear boxes, and a resultant increase in size and weight. Further, there is a limited no break power transfer (NBPT) capability. Also, many components associated with an aircraft require constant frequency power. Thus, complex motor controls have needed to be associated with each of these components to take the variable frequency electric power provided, and transform that into constant frequency power.

0007Aircraft on-board power supplies utilizing a constant frequency generator and a variable frequency generator are proposed, for example, in documents <patcit id="pcit0001" dnum="US2006012177A"><text>US2006012177</text></patcit> and <patcit id="pcit0002" dnum="US4967097A"><text>US4967097</text></patcit>.

SUMMARY OF THE INVENTION

0008An electrical generation system according to claim 1 utilizes a variable frequency generator operating in combination with a constant frequency generator, which generators are driven by a single rotating member through a single gearbox. Also disclosed and claimed are an aircraft electrical system according to claim 4, and a gas turbine engine acording to claim 2 incorporating the above electrical generation system of claim 1. These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

0009<figref idref="f0001">Figure 1</figref> schematically shows an aircraft incorporating the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

0010An aircraft 20 is illustrated schematically in <figref idref="f0001">Figure 1</figref> incorporating a pair of gas turbine engines 22 and 24. As known, the gas turbine engines include a turbine rotor that is driven to rotate by products of combustion.

0011The rotation of the turbine rotor drives a shaft 27, which drives a gearbox 129, which may be an engine-mounted accessory gearbox, which in turn drives two different shafts, each of which powers one of the generators (items 26 &amp; 28) in each engine 22 and 24. The shafts are associated with generators 26 and 28, both shown schematically. As known, as the shaft rotates within the generators 26 and 28, electricity is generated. As disclosed, the generator 28 is a variable frequency generator, and provides variable frequency power to a bus 29.

0012The generator 26 is a constant frequency generator, and may be as known in the art and available from Hamilton Sundstrand Corporation.

0013One known constant frequency generator is disclosed, as an example, in <patcit id="pcit0003" dnum="US6838778B"><text>U.S. Patent 6,838,778</text></patcit>. These generators have not been utilized in combination with a variable frequency generator associated with the same gas turbine engine. The constant frequency generator 26 delivers electricity to a bus 25.

0014In the aircraft 20 as illustrated in <figref idref="f0001">Figure 1</figref>, a number of components 30 are associated with the bus 29. In general, these are components that can utilize variable frequency power. As such, they do not require a complex controller.

0015The bus 25, which is delivering constant frequency power, is associated with other components 32 which do require constant frequency power.

0016With the above described architecture, the system does not require motor controllers for each of the components 32, as has been the case in the past. Thus, the present invention provides a hybrid architecture with the benefits of both variable and constant frequency generator.

0017Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention, as defined by the appended claims.