Electrical power generator for a gas turbine engine

Patent metadata

Field	Value
Publication number	US-9729096-B2
Application number	US-201514608860-A
Country	US
Kind code	B2
Filing date	Jan 29, 2015
Priority date	Feb 24, 2014
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

An aircraft electrical power generation system includes an AC generator having a rotor including a plurality of electromagnetic rotor-windings and stator including plurality of electrical stator-windings. The rotor mechanically coupled to a shaft of a gas turbine engine by transmission-system. The generator includes a frequency controller, a torque sensor determining a torque on the transmission-system by the generator and controller to operate the system in first and second modes. In first mode, the power output frequency of the generator controlled by the frequency controller within limits, and reduced idle signal going to a turbine engine controller. In second mode, the power output frequency of the generator not controlled by the frequency controller and increased idle signal going to the turbine engine controller. The controller operates the system in first mode when the torque is below a limit, and in second mode when the torque is above a limit.

First claim

The invention claimed is:

1. An electrical power generation system for an aircraft gas turbine engine, the system comprising:
a main electrical generator comprising a wound field electrical machine, the main generator having a rotor comprising a plurality of electrical rotor windings and a stator comprising a plurality of electrical stator windings, the rotor being mechanically coupled to a shaft of a gas turbine engine by a transmission arrangement, wherein the electrical power generation system comprises:
an electrical output frequency controller configured to control the frequency of an electrical output of the main electrical generator within a predetermined range of frequencies;
a torque sensor arrangement configured to determine a torque imposed on the transmission arrangement; and
an engine controller configured to increase the rotational speed of the gas turbine engine in the event that the torque imposed on the transmission arrangement exceeds a predetermined torque limit, and to reduce the rotational speed of the gas turbine engine in the event that the torque imposed on the transmission arrangement is less than the predetermined torque limit,
wherein the system is configured to operate in a first mode, in which the frequency of the electrical power output of the electrical machine is actively controlled by the electrical output frequency controller to lie within predetermined limits and the engine controller is configured to operate the gas turbine engine at a reduced idle speed, and in a second mode, in which the frequency of the electrical power output of the electrical machine is not actively controlled by the electrical output frequency controller and the engine controller is configured to operate the gas turbine engine at or above an increased idle speed; wherein the system is configured to operate in the first mode when the torque is below the predetermined torque limit, and in the second mode when the torque is above the predetermined torque limit.

2. A system according to claim 1 , wherein the wound field electrical machine comprises a three phase alternating current electrical generator.

3. A system according to claim 1 , wherein the wound field electrical machine comprises a synchronous electrical machine.

4. A system according to claim 1 , wherein the electrical output frequency controller is configured to provide a multiphase alternating electric current in the electromagnetic windings of the rotor to provide a controllable rotating magnetic field in the rotor.

5. A system according to claim 4 , wherein the system comprises a further generator configured to provide AC electrical power to an input of the electrical output frequency controller.

6. A system according to claim 4 , wherein the system comprises an exciter electrically coupled to an output of the electrical output frequency controller, and an input of the main generator rotor windings.

7. A system according to claim 6 , wherein the exciter comprises a brushless wound field synchronous exciter comprising a stator having a plurality of electrical stator windings, and a rotor having a plurality of electrical rotor windings.

8. A system according to claim 4 , wherein the system further comprise an exciter electrically coupled to an output of an AC power source and an input of the main generator rotor windings, wherein the electrical output frequency controller co-rotates with the main generator rotor, and an input of the electrical output frequency controller is electrically coupled to an output of the exciter rotor windings, and an output of the electrical output frequency controller is electrically coupled to an input of the rotor windings of the main generator.

9. A system according to claim 1 , wherein the generator torque sensor arrangement comprises a torque sensor configured to sense the torque load on the transmission arrangement.

10. A system according to claim 1 , wherein the generator torque sensor arrangement comprises a generator electrical power demand sensor configured to sense electrical load on the generator.

11. A system according to claim 10 , wherein the generator electrical power demand sensor comprises one or more of a current transducer and a voltage transducer.

12. A system according to claim 11 , wherein a current transducer is provided for each electrical phase of the electrical output of the generator.

13. A system according to claim 11 , wherein the generator torque sensor arrangement comprises one or more of a generator electrical power demand sensor, a generator efficiency sensor configured to sense the electrical efficiency of the generator, and a generator power factor sensor configured to sense a phase difference between the electrical phases of the generator.

14. A system according to claim 13 , wherein the generator efficiency sensor comprises one or more of a stator or rotor temperature sensor, a rotor speed sensor and current measurements.

15. A system according to claim 1 , wherein the engine controller is configured to reduce or increase the rotational speed of the engine at a rate less than a predetermined rate.

16. A system according to claim 1 , wherein the generator is configured to switch between the first and second operating modes gradually, such that the output frequency of the generator does not change at a rate greater than a predetermined rate when the generator switches between the first and second operating modes.

17. A method of controlling an electrical power generation system comprising a wound field electrical machine, the wound field electrical machine having a rotor comprising a plurality of electrical rotor windings and a stator comprising a plurality of electrical stator windings, the rotor being mechanically coupled to a shaft of a gas turbine engine by a transmission arrangement, the electrical generator having an electrical output frequency controller, the method comprising:
determining a torque imposed on the transmission arrangement by the generator; and increasing the rotational speed of the gas turbine engine in the event that the torque imposed on the transmission arrangement exceeds a predetermined torque limit, and reducing the rotational speed of the gas turbine engine in the event that the torque imposed on the transmission arrangement is less than the predetermined torque limit, and
operating the electrical power generation system in a first mode when the torque imposed on the transmission arrangement is below the predetermined limit, and in a second mode when the torque imposed on the transmission arrangement is above the predetermined limit, wherein in the first mode, the frequency of the electrical power output of the electrical generator is actively controlled by the electrical output frequency controller to lie within predetermined limits and the gas turbine engine is operated at a reduced idle speed, and in the second mode, the frequency of the electrical power output of the electrical generator is not actively controlled by the electrical output frequency controller and the gas turbine engine is operated at or above an increased idle speed.

18. A method according to claim 17 , wherein, when in the first operating mode, the rotational speed of the reduced idle speed is determined such that the torque does not exceed the predetermined torque limit.

Assignees

• Rolls Royce Plc

Inventors

• Edwards Huw Llewelyn

Classifications

• F05D2220/7642

  of the synchronous type · CPC title

• F02C9/28

  Regulating systems responsive to plant or ambient parameters, e.g. temperature, pressure, rotor speed (F02C9/30 - F02C9/38, F02C9/44 take precedence) · CPC title

• F05D2270/335

  Output power or torque · CPC title

• F05D2270/071

  in particular at idling speed · CPC title

• F01D15/10

  Adaptations for driving, or combinations with, electric generators · CPC title