Electric machine with winding conductors of non-uniform shape
A radial flux rotary electric machine having an exterior-rotor configuration is shown. The machine has a permanent-magnet rotor comprising permanent magnets in a Halbach array, and an air-cored stator interior to the rotor having teeth defining tapered slots and distributed windings around the teeth to form coils in a double-layer arrangement, the windings being comprised of a plurality of phase windings. For each tooth T having a slot S 1 on one side thereof and a slot S 2 on another side thereof, a coil side C 1 of a phase winding is arranged to occupy a radially inner layer of the slot S 1 and a coil side C 2 of the same phase winding is arranged to occupy a radially outer layer of the slot S 2 , wherein the coil side C 1 has a smaller circumferential dimension and a larger radial dimension than the coil side C 2.
1. A radial flux rotary electric machine having an exterior-rotor configuration, comprising:
a permanent-magnet rotor comprising permanent magnets in a Halbach array;
a stator that is air-cored and disposed in an interior of the rotor, and has: (1) teeth defining slots that are tapered, and (2) distributed windings around the teeth to form coils in a double-layer arrangement, the windings being comprised of a plurality of phase windings; and
an inner support on which the permanent magnets are mounted abutting each other in a circumferential direction of the stator,
wherein, for each tooth T having a slot S 1 on one side thereof and a slot S 2 on another side thereof, a coil side C 1 of a phase winding is arranged to occupy a radially inner layer of the slot S 1 and a coil side C 2 of the same phase winding is arranged to occupy a radially outer layer of the slot S 2 , and the coil side C 1 has a smaller circumferential dimension and a larger radial dimension than the coil side C 2 .
2. The rotary electric machine of claim 1 , in which the windings have a constant conductor cross-sectional area.
3. The rotary electric machine of claim 1 , in which the permanent magnets are retained in place by a pre-stressed outer retainer.
4. The rotary electric machine of claim 3 , in which the outer retainer is comprised of one or more of:
a carbon fibre composite;
a metal matrix composite.
5. The rotary electric machine of claim 1 , in which the permanent magnets on the rotor are skewed in an axial sense to reduce cogging torque.
6. The rotary electric machine of claim 1 , in which the permanent magnets on the rotor are separated into axial segments, wherein axially adjacent segments have a circumferential offset therebetween to reduce cogging torque.
7. The rotary electric machine of claim 1 , in which the windings in the stator comprise a transposed conductor.
8. The rotary electric machine of claim 7 , in which the transposed conductor is a litz conductor.
9. The rotary electric machine of claim 1 , in which the coil side C 1 and the coil side C 2 are connected in series.
10. The rotary electric machine of claim 1 , in which the coil side C 1 and the coil side C 2 are connected in parallel.