US2022037979A1PendingUtilityA1
Electric machine
Est. expirySep 18, 2038(~12.2 yrs left)· nominal 20-yr term from priority
Inventors:Paul R. MillerStephen M. HusbandAlexander C. SmithCharalampos ManolopoulosMatteo Iacchetti
B64D 27/31B64D 35/024B64D 27/33H02K 55/04H02K 55/00H02K 3/02H02K 3/14H02K 3/42Y02E40/60H02K 7/1815B64D 2221/00H02K 9/19H02K 2213/03H02K 7/1807H02K 7/1823B64D 2027/026B64D 27/24B64D 27/02B64D 27/026
60
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Claims
Abstract
An electric machine including a stator having a fully non-magnetic core and stator windings formed of a non-superconducting transposed conductor to reduce eddy current losses. It further includes a rotor having a fully non-magnetic core and superconducting windings or superconducting magnets which produce a magnetic field for interaction with the stator windings. A cryogenic cooling system is arranged to cool the stator windings to reduce conduction losses in the stator windings.
Claims
exact text as granted — not AI-modified1 - 15 . (canceled)
16 . A method of operating an electric machine,
the electric machine comprising: a stator having a fully non-magnetic core and stator windings formed of a non-superconducting transposed conductor; a rotor having a fully non-magnetic core and superconducting windings or superconducting magnets which produce a magnetic field for interaction with the stator windings; and a cryogenic cooling system arranged to cool the stator windings, the method comprising: using the cryogenic cooling system, cooling the stator windings to a predetermined temperature of 223 Kelvin or below, the predetermined temperature minimizing a sum of eddy current losses and conduction losses in the stator windings.
17 . The method of claim 16 , in which the predetermined temperature minimizes:
P tot =V ( P eddy +P conduction )
wherein P eddy and P conduction are the eddy current losses and the conduction losses in the stator winding measured in Watts per cubic metre, V is a total volume of the stator windings and P tot is the total losses due to eddy current losses and conduction losses in the stator windings measured in Watts.
18 . The method of claim 16 , in which the predetermined temperature is determined using predetermined conductivity versus temperature data for a material from which the transposed conductor of the stator windings is made.
19 . The method of claim 18 , in which determining the predetermined temperature comprises using the predetermined conductivity versus temperature data and a conductivity value for the transposed conductor of the stator windings.
20 . The method of claim 19 , in which the conductivity value for the transposed conductor of the stator windings is given by:
ρ
=
ω
Br
s
t
r
a
n
d
8
J
S
wherein ρ is the conductivity value of the transposed conductor of the stator windings, r strand is a radius of a strand in the transposed conductor, J s is a current density in the stator windings, B is a magnetic field strength in the transposed conductor of the stator windings, and w is a frequency of the electric machine which is dependent upon a speed of the rotor of the electric and a pole-pair number n for the electric machine.
21 . The method of claim 20 , in which B, the magnetic field strength in the transposed conductor of the stator windings, is the magnetic field at a location D S corresponding to a mean diameter of the stator windings.
22 . The method of claim 21 , in which, D S satisfies:
τ
=
k
τ
J
s
J
r
f
(
D
s
)
k
τ
=
μ
0
π
8
α
h
s
h
r
f
(
D
s
)
=
D
S
3
(
1
-
h
s
+
h
r
+
2
g
D
s
)
n
+
1
wherein:
τ is a torque to be developed by the electric machine;
g is a magnetic airgap length between the stator and the rotor;
J r is a current density in the windings of the rotor;
α is an aspect ratio of the electric machine;
h s is a radial height of the stator windings; and
h r is a radial height of the windings of the rotor.
23 . The method of claim 16 , in which the electric machine is operated at a power of at least 1 MW.
24 . The method of claim 16 , in which the current density in the stator windings is, in operation, at least 8 Amps per square millimetre.
25 . The method of claim 16 , in which the stator windings are supplied with an alternating current at a frequency of at least 800 Hertz.
26 . An electric machine comprising:
a stator having a fully non-magnetic core and stator windings formed of a non-superconducting transposed conductor to reduce eddy current losses; a rotor having a fully non-magnetic core and superconducting windings or superconducting magnets which produce a magnetic field for interaction with the stator windings; and a cryogenic cooling system arranged to cool the stator windings to a predetermined cryogenic temperature of 223 kelvin or below, the predetermined temperature cryogenic temperature minimizing a sum of the eddy current losses and the conduction losses in the stator windings.
27 . The electric machine of claim 26 , in which the transposed conductor is a litz conductor.
28 . The electric machine of claim 26 , in which the stator windings are formed from wire strands having a diameter of less than 1 millimetre.
29 . The electric machine of claim 26 , in which the stator windings are formed from one of:
copper; aluminium.
30 . The electric machine of claim 26 , in which the fully non-magnetic core in the stator comprises a resin.
31 . The electric machine of claim 26 , comprising one of:
8 poles; 16 poles.
32 . A propulsion system for an aircraft, comprising:
an electrical network for distributing electrical power; a source of electrical power connected with the electrical network; and one or more electric machines according to claim 26 connected with the electrical network for driving a fan to propel the aircraft.
33 . The propulsion system of claim 32 , in which at least one of the one or more electric machines drives a boundary layer ingestion fan.
34 . A propulsion system for an aircraft, comprising:
an electrical network for distributing electrical power; one or more electric machines according to claim 26 connected with the electrical network for generating said electrical power; and one or more electric propulsion units connected with the electrical network for propelling the aircraft.
35 . The propulsion system of claim 34 , in which the or each electric machine is driven by a respective internal combustion engine, and optionally wherein the or each internal combustion engine is one of:
a piston engine; a turbomachine.Cited by (0)
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