Varying quantities of motor poles for noise reduction

Patent metadata

Field	Value
Publication number	US-10988035-B2
Application number	US-201916600196-A
Country	US
Kind code	B2
Filing date	Oct 11, 2019
Priority date	Jun 11, 2015
Publication date	Apr 27, 2021
Grant date	Apr 27, 2021

Abstract

An alternating current type electric propulsion system is described that includes an AC generator and a plurality of propulsors electrically coupled to the AC generator. A first propulsor from the plurality of propulsors includes a first motor that drives a first fan of the first propulsor at a first speed. A second propulsor from the plurality of propulsors comprises a second motor that drives a second fan of the second propulsor at a second speed that is different than the first speed.

First claim

What is claimed is:

1. An alternating current (AC) type electric propulsion system, comprising:
a first AC generator having a first quantity of generator pole pairs and a first rotor that spins at a first generator speed;
a first plurality of propulsors electrically coupled to the first AC generator, wherein each propulsor of the first plurality of propulsors comprises a first motor that drives a first fan of the propulsor and has a first quantity of motor pole pairs;
a second AC generator having a second quantity of generator pole pairs and a second rotor that spins at a second generator speed; and
a second plurality of propulsors electrically coupled to the second AC generator, wherein each propulsor of the second plurality of propulsors comprises a second motor that drives a second fan of the second propulsor and has a second quantity of motor pole pairs,
wherein the first AC generator and the first motor are configured to drive the first fan at a first fan speed controlled by a first ratio of the first quantity of generator pole pairs to the first quantity of motor pole pairs,
wherein the second AC generator and the second motor are configured to drive the second fan at a second fan speed, different than the first fan speed, controlled by a second ratio of the second quantity of generator pole pairs to the second quantity of motor pole pairs.

2. The AC type electric propulsion system of claim 1 , wherein:
the first fan speed is based on the first generator speed and the first ratio between the first quantity of generator pole pairs and the first quantity of motor pole pairs; and
the second fan speed is based on the second generator speed and the second ratio between the second quantity of generator pole pairs and the second quantity of motor pole pairs.

3. The AC type electric propulsion system of claim 1 , wherein the first fan speed is based on the second fan speed and at least one of:
a third ratio between the first quantity of motor pole pairs and the second quantity of motor pole pairs, or
a fourth ratio between the first quantity of generator pole pairs and the second quantity of generator pole pairs.

4. The AC type electric propulsion system of claim 1 , wherein:
the first motor drives the first fan of the first propulsor in a first direction; and
the second motor drives the second fan of the second propulsor in a second direction that is opposite the first direction.

5. The AC type electric propulsion system of claim 1 , wherein a third propulsor from the first plurality of propulsors comprises a third motor that drives a third fan of the third propulsor at the first fan speed.

6. The AC type electric propulsion system of claim 5 , wherein:
the first motor drives the first fan of the first propulsor in a first direction; and
the third motor drives the third fan of the third propulsor in the first direction.

7. The AC type electric propulsion system of claim 5 , wherein:
the first motor drives the first fan of the first propulsor in a first direction; and
the third motor drives the third fan of the third propulsor in a second direction that is opposite the first direction.

8. The AC type electric propulsion system of claim 1 , wherein at least one of:
the first AC generator or the second AC generator is configured with reconfigurable stator and rotor windings to change the respective first quantity or second quantity of generator pole pairs, or
the first motor or the second motor is configured with reconfigurable stator and rotor windings to change the respective first quantity or second quantity of motor pole pairs.

9. A method comprising:
selecting, by a controller, a first rotational frequency for a first fan of a first propulsor that is being driven by a first alternating current (AC) generator of an AC type electric distribution system;
selecting, by the controller, a second rotational frequency for a second fan of a second propulsor that is also being driven by a second AC generator of the electric distribution system, wherein the second rotational frequency is different from the first rotational frequency by a frequency variation;
selecting a minimum pole pair offset for differentiating:
a first ratio between a first quantity of generator pole pairs of the first AC generator to control the first fan at the first rotational frequency, and
a second ratio between a second quantity of generator pole pairs of the second AC generator and a second quantity of motor pole pairs of a second motor of the second propulsor to control the second fan at the second rotational frequency;

determining, based on the first rotational frequency and the second rotational frequency and the minimum pole pair offset, a minimum quantity of pole pairs; and
configuring
the first motor to use the minimum quantity of pole pairs as the first quantity of pole pairs.

10. The method of claim 9 , further comprising:
configuring
the second motor to use the minimum quantity of pole pairs plus or minus the minimum pole pair offset as the second quantity of motor pole pairs.

11. The method of claim 9 , further comprising:
configuring a third motor of a third propulsor that drives a third fan to use the first quantity of motor pole pairs.

12. The method of claim 11 , wherein:
configuring the first motor comprises configuring the first motor to spin the first fan in a first direction; and
configuring the third motor comprises configuring the third motor to spin the third fan in a second direction that is opposite the first direction.

13. The method of claim 9 , further comprising:
determining the first rotational frequency for the first fan based on a rotor speed of the first AC generator and the first ratio between the first quantity of generator pole pairs and the first quantity of motor pole pairs.

14. An alternating current (AC) type electric propulsion system comprising:
means for selecting a first rotational frequency for a first fan of a first propulsor that is being driven by a first AC generator of the AC type electric distribution system;
means for selecting a second rotational frequency for a second fan of a second propulsor that is also being driven by a second AC generator of the AC type electric distribution system, the second rotational frequency being different from the first rotational frequency by a frequency variation;
means for selecting a minimum pole pair offset for differentiating:
a first ratio between a first quantity of generator pole pairs of the first AC generator to control the first fan at the first rotational frequency, and
a second ratio between a second quantity of generator pole pairs of the second AC generator and a second quantity of motor pole pairs of a second motor of the second propulsor to control the second fan at the second rotational frequency;

means for determining, based on the first rotational frequency and the second rotational frequency and the minimum pole pair offset, a minimum quantity of pole pairs; and
means for configuring
the first motor to use the minimum quantity of pole pairs as the first quantity of pole pairs.

15. The AC type electric propulsion system of claim 14 , further comprising:
means for configuring
the second motor to use the minimum quantity of pole pairs plus or minus the minimum pole pair offset as the second quantity of pole pairs.

16. The AC type electric propulsion system of claim 14 , further comprising:
means for configuring a third motor of a third propulsor that drives a third fan to use the first quantity of pole pairs.

17. The AC type electric pr

Assignees

• Rolls Royce Corp
• Rolls Royce Nam Tech Inc
• Rolls Royce Plc

Inventors

• Armstrong Michael James
• Blackwelder Mark Jon
• Eames David John Howard
• Chong Ellis Fui Hen

Classifications

• Y02T50/60

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• Y02T50/50

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• B64D35/021

  for electric power plants · CPC title

• B64D31/09

  in response to power plant failure · CPC title

• B64D2041/002

  Mounting arrangements for auxiliary power units (APU's) · CPC title