An alignment fixture includes a rotor fixture, a stator fixture and a sensor system which measures a rotational displacement therebetween. The fixture precisely measures rotation of a generator stator assembly away from a NULL position referenced by a unique reference spline on the rotor shaft. By providing an adjustable location of the stator assembly within the housing, the magnetic axes within each generator shall be aligned to a predetermined and controlled tolerance between the generator interface mounting pin and the reference spline on the rotor shaft. Once magnetically aligned, each generator is essentially a line replaceable unit which may be readily mounted to any input of a multi-generator gearbox assembly with the assurance that the magnetic alignment will be within a predetermined tolerance.
BACKGROUND OF THE INVENTION
This invention was made with government support under Contract No.: F19628-03-0014. The government therefore has certain rights in this invention.
The present invention relates to a generator system, and more particularly to an alignment fixture therefor.
Vehicles, such as aircraft, utilize an electric generator system to provide electric power. The generators convert mechanical energy from rotation of the engine into electrical energy for the vehicle.
Oftentimes, vehicles such as aircraft require more power than a single generator can provide and utilize a multiple of generators on a multi-headed gearbox all driven by a common drivetrain. To allow for optimum parallel operation, each generator that feeds a common electrical bus is required to be synchronized with every other generator to which it is hard connected through the geartrain so that the voltage of each generator is in phase.
The mechanical alignment of the each coupled rotor to the common drive train defines the angular position of the rotor magnetic axis in its respective generator and thus the phasing of its alternating voltage. The voltage of two or more generators must be in phase with each other within a predetermined angular separation to permit connecting them in parallel. Assuming all the generators to be paralleled are identical and the magnetic axes aligned with each other, conventional mechanical alignment requires the housing assembly of each generator to be individually rotationally adjusted or "timed" relative the gearbox assembly to accommodate the magnetic variance and align the output phasing of each generator to each other generator. Although effective, such individualistic mounting may be relatively time consuming from a maintenance perspective. Adjustment to a multiple of generators is also often required whenever a single generator requires replacement which may still further increase maintenance down time.
Accordingly, it is desirable to provide an electric generator assembly system that accommodates electrical and mechanical variance and produces multiple generators all demonstrating similar angular relationship between individual output phasing and mounting interface position which results in apparently identical generators that minimizes individualized mounting alignment and maintenance concerns.