Free turbine turbogenerator comprising a reversible electrical machine coupled to the free turbine

A turbomachine of a free turbine turbogenerator type, comprising a gas generator equipped with a first mechanical shaft, at least one reversible electrical machine and a free turbine provided with a second mechanical shaft and caused to rotate by a gas flow generated by the gas generator,

• wherein said second mechanical shaft is mechanically connected to said at least one reversible electrical machine and the free turbine during all phases of operation of the turbomachine, and
• the turbomachine further comprises a single mechanical coupling means configured to mechanically couple said first mechanical shaft to said second mechanical shaft when said at least one reversible electrical machine is operating in motor mode and mechanically uncoupling said first mechanical shaft from said second mechanical shaft when said at least one reversible electrical machine is operating in generator mode,
• said at least one reversible electrical machine configured to drive the gas generator and the free turbine during start-up of the turbomachine,
• wherein said single mechanical coupling means comprises a free wheel and at least one intermediate pinion mounted between the free wheel and the first mechanical shaft, and
• wherein the at least one intermediate pinion includes a first wheel and a second wheel mounted between the first mechanical shaft and the free wheel,
• wherein a control unit of said at least one reversible electrical machine is configured to:
• measure a torque exerted by the second mechanical shaft on an output of the free wheel mechanically connected to the first mechanical shaft;
• determine the measured torque is less than a torque threshold;
• determine the gas generator is autonomous when the measured torque is less than the torque threshold;
• and
• place the at least one reversible electrical machine in the generator mode upon determining the gas generator is autonomous.