Abstract: Electromechanical arrangements are utilised widely whereby a prime mover in the form of a mechanical assembly such as a gas turbine engine is utilised to drive an electrical machine as an electrical generator. Unfortunately the loads applied to the electrical generator may vary creating oscillation across phases of the electrical generator. Such oscillations generally will be translated to the mechanical assembly in the form of torque oscillations which may cause stressing. Stressing of the mechanical assembly will reduce its life and may alter its performance as well as fuel consumption. By provision of appropriate mechanisms for balancing electrical loads across an electrical machine as well reducing the time decay period for stored charge within an electrical assembly associated with an electrical machine it is possible to reduce torque oscillations as presented to the mechanical assembly and therefore improve its operational performance.

Abstract: A gas turbine engine arrangement (1) comprises a first gas turbine engine (10), a second gas turbine engine (70), a differential gearbox (57) and an electrical generator (112). The differential gearbox (57) has a first input drive (54), a second input drive (78) and an output drive (110). The output drive (110) of the differential gearbox (57) is arranged to drive the electrical generator (112) via an external, accessory, gearbox (56). The external, accessory, gearbox (56) drives other accessories (116, 120). The first gas turbine (10) is arranged to drive the first input drive (54) of the differential gearbox (57) and the second gas turbine engine (70) is arranged to drive the second input drive (78) of the differential gearbox (57). The electrical generator (112) and accessories (116, 120) are driven at a constant frequency speed/frequency.