Gas turbine engine starter generator that selectively changes the number of rotor poles

Abstract

A rotating electrical machine, such as an aircraft starter-generator, that may be operated in either a motor mode or an generator mode. The machine includes a main rotor that is selectively configurable as an M-pole rotor or an N-pole rotor. The machine can also include DC brushes that are selectively moveable into, and out of, electrical contact the main rotor, to thereby electrically couple and decouple a DC power source to and from, respectively, the rotor windings.

We claim:  
     
         1 . A gas turbine engine starter-generator, comprising: 
 a housing;    a main stator mounted within the housing; and    a main rotor mounted within the housing and located at least partially within at least a portion of the main stator, the main rotor selectively configurable as either an M-pole rotor or an N-pole rotor.    
     
     
         2 . The starter-generator of  claim 1 , further comprising: 
 a control circuit electrically coupled to at least the main rotor and operable to selectively configure the main rotor as the M-pole rotor or the N-pole rotor.    
     
     
         3 . The starter-generator of  claim 2 , further comprising: 
 a plurality of windings wound on at least a portion of the main rotor; and    a switch electrically coupled between selected ones of the main rotor windings, the switch having at least a first position and a second position,    wherein the main stator is configured as the M-pole rotor with the switch in the first position, and is configured as the N-pole stator with the switch in the second position.    
     
     
         4 . The starter-generator of  claim 3 , wherein the control circuit comprises: 
 switch control circuitry operable to move the switch between at least the first position and the second position.    
     
     
         5 . The starter-generator of  claim 5 , further comprising: 
 at least two brushes adapted to electrically couple to a DC power source and selectively moveable into, and out of, electrical contact with at least a portion of the main rotor, whereby the brushes are electrically coupled to, and decoupled from, respectively, the main rotor windings.    
     
     
         6 . The starter-generator of  claim 5 , further comprising: 
 an exciter rotor mounted on the shaft;    an exciter stator having a plurality of windings wound thereon, the exciter stator mounted within the housing and located at least partially around at least a portion of the exciter rotor; and    at least one rectifier assembly electrically coupled in series between the exciter stator windings and the main rotor windings.    
     
     
         7 . The starter-generator of  claim 1 , wherein M is unequal to N.  
     
     
         8 . The starter-generator of  claim 7 , wherein N=(M/2).  
     
     
         9 . A gas turbine engine starter-generator, comprising: 
 a housing;    a shaft rotationally mounted within the housing;    a main rotor mounted on the shaft;    a main stator mounted within the housing and located at least partially around at least a portion of the main rotor;    a plurality of main rotor windings wound around at least a portion of the main rotor; and    a switch electrically coupled between selected ones of the main rotor windings and having at least a first position and a second position,    wherein the switch, when in the first position, electrically couples the main rotor windings such that the main rotor is configured as an M-pole rotor and, when in the second position, electrically couples the main rotor windings such that the main rotor is configured as an N-pole rotor.    
     
     
         10 . The starter-generator of  claim 9 , further comprising: 
 a control circuit operable to selectively move the switch between the first and second positions.    
     
     
         11 . The starter-generator of  claim 10 , wherein the control circuit includes: 
 switch control circuitry operable to selectively move the switch between the first and second positions.    
     
     
         12 . The starter-generator of  claim 20 , further comprising: 
 a plurality of main stator windings wound on at least a portion of the main stator, each of the main stator windings adapted to selectively electrically couple to a DC power source.    
     
     
         13 . The starter-generator of  claim 9 , further comprising: 
 at least two brushes adapted to electrically couple to a DC power source and selectively moveable into, and out of, electrical contact with at least a portion of the main rotor, whereby the brushes are electrically coupled to, and decoupled from, respectively, the main rotor windings.    
     
     
         14 . The starter-generator of  claim 9 , further comprising: 
 an exciter rotor mounted on the shaft;    an exciter stator having a plurality of windings wound thereon, the exciter stator mounted within the housing and located at least partially around at least a portion of the exciter rotor; and    at least one rectifier assembly electrically coupled in series between the exciter stator windings and the main rotor windings.    
     
     
         15 . The starter generator of  claim 9 , further comprising: 
 a DC power source electrically coupled in series with the main rotor when the main rotor is configured as an N-pole rotor.    
     
     
         16 . The starter-generator of  claim 9 , wherein M is unequal to N.  
     
     
         17 . The starter-generator of  claim 16 , wherein N=(M/2).  
     
     
         18 . A rotor for a gas turbine engine starter-generator, comprising: 
 a main rotor body; and    a plurality of rotor coils wound around at least a portion of the main body,    wherein the rotor coils are wound in a configuration that allows the rotor to be selectively configured as an M-pole rotor or an N-pole rotor.    
     
     
         19 . The rotor of  claim 18 , further comprising: 
 a switch electrically coupled between selected ones of the rotor coils and having at least a first position and a second position.    
     
     
         20 . The rotor of  claim 19 , wherein the rotor is configured as the M-pole rotor with the switch in the first position, and is configured as the N-pole rotor with the switch in the second position.  
     
     
         21 . The rotor of  claim 19 , wherein M is unequal to N.  
     
     
         22 . The rotor of  claim 21 , wherein N=(M/2).  
     
     
         23 . A device for placement in a gas turbine engine starter-generator, comprising: 
 a controllable actuator moveable between at least a first position and a second position; and    one or more DC brushes coupled to the actuator.    
     
     
         24 . The device of  claim 23 , wherein: 
 the actuator is adapted to receive a control signal; and    the actuator is responsive to the control signal to move between at least the first and second positions.    
     
     
         25 . In a motor/generator including a stator having a plurality of stator windings wound around at least a portion thereof and a rotor having a plurality of rotor windings wound around at least a portion thereof, a method of operating the motor/generator, comprising: 
 electrically coupling at least a portion of the rotor windings together such that the main rotor is configured as an N-pole rotor;    supplying DC power to the electrically coupled rotor windings and to the stator windings, to thereby operate the motor/generator as a DC motor; and    electrically coupling at least a portion of the rotor windings together such that the main rotor is configured as an M-pole rotor and no longer supplying DC power to the stator windings, to thereby operate the motor/generator as an AC generator.    
     
     
         26 . The method of  claim 25 , wherein the motor/generator further includes at least two brushes that are selectively electrically coupled to, and decoupled from, the rotor windings, the method further comprising: 
 electrically coupling the brushes to the rotor windings when operating the motor/generator as a DC motor; and    electrically decoupling the brushes from the from rotor windings when operating the motor/generator as an AC generator.    
     
     
         27 . The method of  claim 25 , wherein the motor/generator changes from operation as a DC motor to an AC generator when its rotational speed reaches a predetermined magnitude.  
     
     
         28 . The method of  claim 25 , wherein the motor/generator changes from operation as a DC motor to an AC generator a predetermined time after commencing operation as a DC motor.