# US 12,603,551 B2 · Hybrid liquid and air cooling of high-power permanent magnet machine rotor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,603,551 B2 - Document ID: US12603551B2 - Status: Granted - Kind: B2 - Application number: 18/330,816 - Filed: 2023-06-07 - Published: 2024-12-12 - Granted: 2026-04-14 - Earliest claimed: 2023-06-07 - Assignees: Hamilton Sundstrand Corporation - Applicants: Hamilton Sundstrand Corporation - Inventors: Ashutosh Joshi; Debabrata Pal; Andreas C. Koenig - Web page: https://patentgrep.com/patent/US12603551B2 ## CPC - H02K 9/197: in which the rotor or stator space is fluid-tight, e.g. to provide for different cooling media for rotor and stator - F01D 15/10: Adaptations for driving, or combinations with, electric generators - H02K 1/278: Surface mounted magnets; Inset magnets - H02K 5/203: {specially adapted for liquids, e.g. cooling jackets} - H02K 5/207: {with openings in the casing specially adapted for ambient air} - H02K 9/02: by ambient air flowing through the machine - H02K 9/04: having means for generating a flow of cooling medium - H02K 9/10: by gaseous cooling medium flowing in closed circuit, a part of which is external to the machine casing - H02K 21/14: with magnets rotating within the armatures - F04D 25/06: the pump being electrically driven (F04D25/08 takes precedence) - F04D 29/5806: {Cooling the drive system} - H02K 7/1823: {structurally associated with turbines or similar engines} - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) - F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D) - F04D: NON-POSITIVE-DISPLACEMENT PUMPS (engine fuel-injection pumps F02M; ion pumps H01J41/12; electrodynamic pumps H02K44/02) ## Abstract An electric machine includes a housing, a stator positioned in the housing and including a stator winding, and a rotor positioned in the housing configured to rotate about a machine axis and electromagnetically interactive with the stator across an air gap between the rotor and the stator. The rotor includes a rotor core, a plurality of permanent magnets located at the rotor core, and a rotor sleeve enclosing the rotor core and the plurality of permanent magnets. The stator is cooled via a flow of cooling oil, and the rotor is cooled via a flow of cooling air directed through the air gap between the rotor sleeve and the stator. ## Claims ### Claim 1 An electric machine, comprising: a housing: a stator disposed in the housing and including a stator winding; and a rotor disposed in the housing configured to rotate about a machine central axis and electromagnetically interact with the stator across an air gap between the rotor and the stator, the rotor including: a rotor core; a plurality of permanent magnets disposed at the rotor core; a rotor sleeve enclosing the rotor core and the plurality of permanent magnets; wherein the stator is configured to be cooled via a flow of cooling oil; and wherein the rotor is configured to be cooled via a flow of cooling air directed through the air gap between the rotor sleeve and the stator; further comprising a cooling airflow inlet at a first axial end of the housing and a cooling airflow outlet at a second axial end of the housing to direct the flow of cooling air through the air gap; wherein the flow of cooling air is ambient airflow directed into the cooling airflow inlet; and wherein the flow of cooling air is directed from the cooling airflow outlet to an air inlet of an auxiliary power unit operably connected to the electric machine to power the electric machine. ### Claim 2 (depends on 1) The electric machine of claim 1, wherein the stator includes a stator sleeve, such that the air gap is at least partially defined between the stator sleeve and the rotor sleeve, the stator sleeve and the housing defining a stator chamber to contain the flow of cooling oil. ### Claim 3 (depends on 2) The electric machine of claim 2, wherein the stator sleeve and the rotor sleeve are configured such the flow of cooling air is directed therebetween. ### Claim 4 (depends on 1) The electric machine of claim 1, wherein the flow of cooling air is one of an ambient airflow or a bleed airflow from the auxiliary power unit. ### Claim 5 An electric machine system, comprising: an auxiliary power unit; and an electric machine operably connected to the auxiliary power unit to drive the electric machine, the electric machine including: a housing: a stator disposed in the housing and including a stator winding; and a rotor disposed in the housing configured to rotate about a machine central axis and electromagnetically interact with the stator across an air gap between the rotor and the stator, the rotor including: a rotor core; a plurality of permanent magnets disposed at the rotor core; a rotor sleeve enclosing the rotor core and the plurality of permanent magnets; wherein the stator is configured to be cooled via a flow of cooling oil; and wherein the rotor is configured to be cooled via a flow of cooling air directed through the air gap between the rotor sleeve and the stator; further comprising a cooling airflow inlet at a first axial end of the housing and a cooling airflow outlet at a second axial end of the housing to direct the flow of cooling air through the air gap; wherein the flow of cooling air is ambient airflow directed into the cooling airflow inlet; and wherein the flow of cooling air is directed from the cooling airflow outlet to an air inlet of the auxiliary power unit. ### Claim 6 (depends on 5) The electric machine system of claim 5, wherein the stator includes a stator sleeve, such that the air gap is at least partially defined between the stator sleeve and the rotor sleeve, the stator sleeve and the housing defining a stator chamber to contain the flow of cooling oil. ### Claim 7 (depends on 6) The electric machine system of claim 6, wherein the stator sleeve and the rotor sleeve are configured to direct the flow of cooling air therebetween. ### Claim 8 (depends on 5) The electric machine system of claim 5 wherein the flow of cooling air is a bleed airflow from a compressor of the auxiliary power unit. ### Claim 9 (depends on 5) The electric machine system of claim 5, wherein the auxiliary power unit includes one of a gas turbine engine or a thermal engine. ### Claim 10 A method of cooling an electric machine, comprising: directing a flow of cooling oil into a stator cavity defined between a stator sleeve and a housing of the electric machine and containing one or more stator windings; cooling the one or more stator windings via the flow of cooling oil; directing a flow of cooling air through an air gap defined between a rotor sleeve of a rotor of the electric machine and the stator sleeve; cooling one or more permanent magnets of the rotor via the flow of cooling air; flowing an ambient airflow into the air gap via a cooling airflow inlet as the flow of cooling air; flowing the flow of cooling air out of the electric machine via a cooling airflow outlet; and directing the flow of cooling air from the cooling airflow outlet into an air inlet of an auxiliary power unit operably connected to the electric machine. ### Claim 11 (depends on 10) The method of claim 10, wherein the stator sleeve separates the flow of cooling oil from the flow of cooling air. ### Claim 12 (depends on 10) The method of claim 10, further comprising: combusting a mixture of fuel and the flow of cooling air at the auxiliary power unit; and driving rotation of the rotor of the electric machine via a flow of combustion gases over a turbine of the auxiliary power unit. ### Claim 13 (depends on 10) The method of claim 10, further comprising flowing a compressor bleed flow of the auxiliary power unit into the cooling airflow inlet as the flow of cooling air.