Electrical machines for aircraft power and propulsion systems

An electrical propulsion unit (EPU) for an aircraft, the EPU comprising:

• a propeller or a fan;
• and
• a transverse flux electric motor having a stator and a rotor drivingly coupled to a rotating shaft of the propeller or the fan,
• wherein the rotor has a plurality of circumferentially distributed permanent magnets that form a number, NP, of rotor poles, wherein the rotor poles have a pole pitch angle, Pθ, equal to 2π divided by the number of rotor poles, NP,
• wherein the stator has a plurality of current-carrying coils configured to interact with the rotor poles of the rotor to produce a torque, and
• wherein an air gap separates the rotor from the stator by an air gap distance, GAir,
• wherein a machine parameter, , defined as:
• Υ
• =
• P
• θ
• ×
• G
• Air
• is less than 100 micro radian-meters,
• wherein an active parts torque density, βact, of the transverse flux electrical motor is defined as:
• ρ
• act
• =
• τ
• peak
• m
• act
• wherein τpeak is a peak rated torque of the transverse flux electrical motor and mact is an active parts mass of the transverse flux electrical motor,
• wherein the active parts mass is a cumulated mass of components of the transverse flux electrical motor that contribute to producing the torque, and
• wherein ρact is in a range of 50 to 165 Nmkg−1.

A vertical take-off and landing (VTOL) aircraft comprising:

• an electrical propulsion unit (EPU) comprising:
• a propeller or a fan;
• and
• a transverse flux electric motor having a stator and a rotor drivingly coupled to a rotating shaft of the propeller or the fan,
• wherein the rotor has a plurality of circumferentially distributed permanent magnets that form a number, NP, of rotor poles, wherein the rotor poles have a pole pitch angle, Pθ, equal to 2π divided by the number of rotor poles, NP,
• wherein the stator has a plurality of current-carrying coils configured to interact with the rotor poles of the rotor to produce a torque, and
• wherein an air gap separates the rotor from the stator by an air gap distance, GAir,
• wherein a machine parameter, , defined as:
• Υ
• =
• P
• θ
• ×
• G
• Air
• is less than 100 micro radian-meters,
• wherein an active parts torque density, ρact, of the transverse flux electrical motor is defined as:
• ρ
• act
• =
• τ
• peak
• m
• act
• wherein τpeak is a peak rated torque of the transverse flux electrical motor and mact is an active parts mass of the transverse flux electrical motor,
• wherein the active parts mass is a cumulated mass of components of the transverse flux electrical motor that contribute to producing the torque, and
• wherein ρact is in a range of 50 to 165 Nmkg−1.