Engine start system with quadrature ac excitation

An engine starting system, comprising:

• a shaft, wherein sufficient rotation of the shaft starts the engine;
• a main starter-generator stator with a plurality of main stator windings wound thereon;
• a main starter-generator rotor mounted on the shaft and disposed at least partially within the main starter-generator stator, the main starter-generator rotor having a plurality of main starter-generator rotor windings wound thereon to generate an air gap flux when they are electrically excited;
• an exciter rotor mounted on the shaft, the exciter rotor having a plurality of exciter rotor windings wound thereon;
• an exciter stator surrounding at least a portion of the exciter rotor, the exciter stator having a plurality of exciter stator windings wound thereon;
• and
• an exciter controller electrically coupled to the exciter stator windings, the exciter controller configured to provide electrical excitation to the exciter stator windings.

An aircraft starter-generator system to start an aircraft gas turbine engine as the prime mover, the system comprising:

• a housing;
• a drive shaft rotationally mounted within the housing and transmitting power to the prime mover;
• a main starter-generator stator mounted within the housing and having a plurality of main starter-generator stator windings wound thereon;
• a main starter-generator rotor mounted on the drive shaft and disposed within the main starter-generator stator, the main starter-generator rotor having a plurality of main starter-generator rotor windings wound thereon configured to receive a two-phase excitation current, wherein the main starter-generator rotor windings generate an air gap flux upon electrical excitation thereof;
• an exciter rotor mounted on the drive shaft, the exciter rotor having a plurality of exciter rotor windings wound thereon, the exciter rotor windings electrically connected to the main starter-generator rotor;
• an exciter stator surrounding the exciter rotor, the exciter stator having a plurality of exciter stator windings wound thereon, the exciter stator windings configured, upon electrical excitation thereof, to electrically excite the exciter rotor windings, wherein
• interaction between current in the main starter-generator stator and the air gap flux creates a starting torque to turn the shaft to start the engine, and
• voltage supplied to the exciter stator winding controls the current in the main starter-generator rotor and the starting torque.