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US 2020/0047897 A1Published application
Varying quantities of motor poles for noise reduction
AssigneesROLLS-ROYCE plc, Rolls-Royce North American Technologies Inc.
InventorsMichael James Armstrong, Mark Jon Blackwelder, David John Howard Eames, Ellis Fui Hen Chong
Life of this patent
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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.
Claims20
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,
- 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, and
- wherein at least one of:
- the second quantity of generator pole pairs is different than the first quantity of generator pole pairs;
- or
- the second quantity of motor pole pairs is different than the first quantity of motor pole pairs.
8 more elements
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 at least one of:
- a first quantity of generator pole pairs of the first AC generator from a second quantity of generator pole pairs of the second AC generator, or
- a first quantity of motor pole pairs of a first motor of the first propulsor from a second quantity of motor pole pairs of a second motor of the second propulsor;
- 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 at least one of:
- the first AC generator to use the minimum quantity of pole pairs as the first quantity of generator pole pairs, or
- the first motor to use the minimum quantity of pole pairs as the first quantity of pole pairs.
7 more elements
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 at least one of:
- a first quantity of generator pole pairs of the first AC generator from a second quantity of generator pole pairs of the second AC generator, or
- a first quantity of motor pole pairs of a first motor of the first propulsor from a second quantity of motor pole pairs of a second motor of the second propulsor;
- 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 at least one of:
- the first AC generator to use the minimum quantity of pole pairs as the first quantity of generator pole pairs, or
- the first motor to use the minimum quantity of pole pairs as the first quantity of pole pairs.
7 more elements
Dependencies are inferred from the claim text.