Turbine engine starter/generator, and method for the control thereof

A turbine engine starter-generator comprising:

• a main electrical machine configured to operate in synchronous electricity generator mode after the turbine engine has started and to operate in electric motor mode during a stage of starting the turbine engine, the main electrical machine having a stator carrying stator windings and a rotor with a wound rotor inductor and damper bars forming a cage by being electrically connected to one another at their ends;
• an exciter including a stator inductor and a rotor with rotor windings connected to the rotor inductor of the main electrical machine via a rotary rectifier, the rotors of the main electrical machine and of the exciter being mounted on a common shaft for coupling mechanically to a shaft of the turbine engine;
• a generator regulation unit connected to the stator inductor of the exciter to supply DC to the stator inductor of the exciter while the main electrical machine is operating in synchronous electricity generator mode;
• and
• a starter regulation unit connected to the stator windings of the main electrical machine via a starting contact in order to deliver AC to the stator windings of the main electrical machine while it is operating in electric motor mode;
• the starter regulation unit including a first regulator circuit for starting in asynchronous motor mode, a second regulator circuit for starting in synchronous motor mode, an inverter for delivering the AC to the stator windings of the main electrical machine via the starting contactor, a motor mode switch for causing the inverter to be controlled by the first or the second starting regulator circuit, and a control circuit for controlling the motor mode switch and the starting contactor, the control circuit receiving information representative of the speed of rotation of the shaft and configured to:
• close the starting contactor in response to an order to start;
• begin starting of the turbine engine with the main electrical machine operating in asynchronous mode by the regulator circuit for starting in asynchronous motor mode;
• continue starting with the main electrical machine operating in synchronous motor mode by the regulator circuit for starting in synchronous mode, the change from asynchronous motor mode to synchronous motor mode being made when the speed of rotation of the shaft exceeds a predetermined threshold;
• and
• after the turbine engine has started and ignited, opening the starting contactor so as to enable the electrical machine to operate in synchronous generator mode;
• and
• the cage formed by the damper bars configured to make starting in asynchronous motor mode possible without the rotor inductor of the main electrical machine contributing to generating the starting torque by being short-circuited.