Electrically starting a gas turbine engine

Patent metadata

Field	Value
Publication number	US-12515809-B2
Application number	US-202418672921-A
Country	US
Kind code	B2
Filing date	May 23, 2024
Priority date	Jun 19, 2023
Publication date	Jan 6, 2026
Grant date	Jan 6, 2026

Abstract

An aircraft power and propulsion system includes a gas turbine engine having first and second spools, the first spool being a starting spool; first and second DC electrical networks having first and second operating voltages; a first electrical machine joined with the first spool, the first electrical machine having first and a second winding sets; a second electrical machine joined with the second spool; a first, second and third AC:DC converter; and a controllable switching arrangement configured so that a connection to an AC-side of the third AC:DC converter is switchable between a winding of the second electrical machine or the second DC electrical network via an inductor.

First claim

The invention claimed is:

1 . An aircraft power and propulsion system, comprising:
a gas turbine engine having a first spool and a second spool, the first spool being a designated starting spool; a first DC electrical network having a first operating voltage; a second DC electrical network having a second operating voltage different from the first operating voltage; a first electrical machine mechanically coupled with the first spool, the first electrical machine having a first winding set and a second winding set; a second electrical machine mechanically coupled with the second spool; a first AC:DC converter, wherein an AC-side of the first AC:DC converter is connected to the first winding set of the first electrical machine, and a DC-side of the first AC:DC converter is connected to the first DC electrical network; a second AC:DC converter, wherein an AC-side of the second AC:DC converter is connected to the second winding set of the first electrical machine, and a DC-side of the second AC:DC converter connected to the second DC electrical network; a third AC:DC converter, a DC-side of the third AC:DC converter connected to the first DC electrical network; a controllable switching arrangement configured so that a connection to an AC-side of the third AC:DC converter is switchable between: a winding of the second electrical machine; and the second DC electrical network via an inductor.

2 . The aircraft power and propulsion system of claim 1 , wherein:
the first electrical machine is rated to produce at least a rated starting torque, tstart, of the engine; and a current required by the first winding set of the first electrical machine to produce the starting torque is greater than a rated current output of the first AC:DC converter.

3 . The aircraft power and propulsion system of claim 1 , wherein:
the first operating voltage is greater than the second operating voltage, and wherein the third AC:DC converter is operable as a buck-mode DC:DC converter; or the first operating voltage is lower than the second operating voltage, and wherein the third AC:DC converter is operable as a boost-mode DC:DC converter.

4 . The aircraft power and propulsion system of claim 1 , comprising a control system configured to:
in response to a request to start or restart the gas turbine engine, control the switching arrangement to disconnect the AC-side of the third AC:DC converter from the winding of the second electrical machine and to connect the AC-side of the third AC:DC converter to the second DC electrical network; and operate the third AC:DC converter and inductor as a DC:DC converter.

5 . The aircraft power and propulsion system of claim 1 , comprising a control system configured to:
following an engine start or restart, stop current flow through the third AC:DC converter by controlling a switching state of one or more transistors of the third AC:DC converter; and after stopping current flow through the third AC:DC converter, controlling the switching arrangement to disconnect the AC-side of the third AC:DC converter from the second DC electrical network and the inductor, and to connect the AC-side of the third AC:DC converter to the winding of the second electrical machine.

6 . The aircraft power and propulsion system of claim 1 , wherein the first winding set of the first electrical machine has a first number of turns, and the second winding set of the first electrical machine has a second number of turns different from the first number of turns.

7 . The aircraft power and propulsion system of claim 1 , wherein the first winding set of the first electrical machine is connected in a star configuration, and the second winding set of the first electrical machine is connected in a delta configuration.

8 . The aircraft power and propulsion system of claim 1 , wherein:
the winding of the second electrical machine is a first winding set of the second electrical machine; the second electrical machine further comprises a second winding set; and the aircraft power and propulsion system further comprises a fourth AC:DC converter, wherein an AC-side of the fourth AC:DC converter is connected to the second winding set of the second electrical machine, and a DC-side of the fourth AC:DC converter is connected to the second DC electrical network.

9 . The aircraft power and propulsion system of claim 8 , wherein the first winding set of the second electrical machine has a first number of turns, and the second winding set of the second electrical machine has a second number of turns different from the first number of turns.

10 . The aircraft power and propulsion system of claim 8 , wherein the first winding set of the second electrical machine is connected in a star configuration, and the second winding set of the second electrical machine is connected in a delta configuration.

11 . The aircraft power and propulsion system of claim 8 , wherein:
the inductor is a transformer having a first winding and a second winding; the controllable switching arrangement is configured so that: the connection to the AC-side of the third AC:DC converter is switchable between the first winding set of the second electrical machine and the first winding of the transformer; and the connection to the AC-side of the fourth AC:DC converter is switchable between the second winding set of the second electrical machine and the second winding of the transformer.

12 . The aircraft power and propulsion system of claim 11 , comprising a control system configured to, in response to a request to start or restart the gas turbine engine:
control the switching arrangement to disconnect the AC-side of the third AC:DC converter from the first winding set of the second electrical machine and to connect the AC-side of the third AC:DC converter to the first winding of the transformer; control the switching arrangement to disconnect the AC-side of the fourth AC:DC converter from the second winding set of the second electrical machine and to connect the AC-side of the fourth AC:DC converter to the second winding of the transformer; and operate the third AC:DC converter, the fourth AC:DC converter and the transformer as a DC:DC converter.

13 . The aircraft power and propulsion system of claim 11 , comprising a control system configured to:
following an engine start or restart, stop current flow through the third and fourth AC:DC converters by controlling a switching state of one or more transistors of each of the third and further AC:DC converters; and after stopping current flow through the third and fourth AC:DC converters: controlling the switching arrangement to disconnect the AC-side of the third AC:DC converter from the first winding of the transformer and to disconnect the AC-side of the fourth AC:DC converter from the second winding of the transformer; and controlling the switching arrangement to connect the AC-side of the third AC:DC converter to the first winding set of the second electrical machine and to connect the AC-side of the fourth AC:DC converter to the second winding set of the second electrical machine.

14 . The aircraft power and propulsion system of claim 1 , wherein:
the gas turbine engine is a two-spool gas turbine engine, the first spool is a high-pressure spool, and the second pool is a low-pressure spool; or the gas turbine engine is a three-spool gas turbine engine, the first spool is an high pressure (HP) spool, and the second spool is an intermediate-pressure (IP) spool or low pressure (LP) spool; or the gas turbine engine is a three-spool gas turbine engine, the first spool is an IP spool, and the sec

Assignees

• Rolls Royce Plc

Inventors

• Trainer David R
• Sweet Mark
• Cartwright Matthew S

Classifications

• H02P9/08

  Control of generator circuit during starting or stopping of driving means, e.g. for initiating excitation · CPC title

• F05D2260/85

  Starting · CPC title

• F02C7/26

  Starting; Ignition · CPC title

• B64D2221/00

  Electric power distribution systems onboard aircraft · CPC title

• B64D27/10

  of gas-turbine type  (jet aircraft B64D27/16) · CPC title