Motor/generator and motor drive circuit
Apparatus for use as a motor or generator, comprising: a first part; a second part movable relative to the first part and spaced from the first part by an air gap; and a plurality of spaced electromagnet elements ( 120 ) provided on the first part, each electromagnet element being operative to apply a magnetic field in the air gap in response to application of an electric current; wherein each electromagnet element comprises: a pole piece comprising: an outer section ( 124 A, 124 B) defining an elongate air-gap facing surface ( 125 A) of area A 1 , perimeter P 1 , lateral width W 1 , and longitudinal length L 1 , wherein Li is greater than W1; and a coil-winding section of cross-sectional area A 2 , cross-sectional perimeter P 2 , lateral width W 2 , and longitudinal length L 2 ; and an electrically conductive coil ( 128 ) wound around the coil-winding section of the pole piece; characterised in that P 2 is less than P 1 and in that W 2 is substantially equal to L 2 .
1. Apparatus for use as a motor or generator, comprising:
a first part;
a second part movable relative to the first part and spaced from the first part by an air gap; and
a plurality of laterally spaced electromagnet elements provided on the first part, each electromagnet element being operative to apply a magnetic field in the air gap in response to application of an electric current;
wherein each electromagnet element comprises:
a pole piece comprising:
an outer section defining an elongate air-gap facing surface of area A 1 , perimeter P 1 , lateral width W 1 , and longitudinal length L 1 , wherein L 1 is greater than W 1 ; and
a coil-winding section of cross-sectional area A 2 , cross-sectional perimeter P 2 , lateral width W 2 , and longitudinal length L 2 ; and
an electrically conductive coil wound around the coil-winding section of the pole piece;
wherein P 2 is less than P 1 , W 2 is substantially equal to L 2 , and A 2 >A 1 .
2. Apparatus according to claim 1 , wherein P 2 is less than or equal to 0.9 times P 1 .
3. Apparatus according to claim 1 , wherein W 2 is greater than W 1 .
4. Apparatus according to claim 3 , wherein W 2 ≥1.5x W 1 .
5. Apparatus according to claim 1 , wherein the coil-winding section has a substantially circular cross-section of diameter D.
6. Apparatus according to claim 1 , wherein the air-gap facing surface is substantially rectangular.
7. Apparatus according to claim 1 , wherein the first part is rotatable relative to the second part about a rotary axis and the plurality of electromagnet elements are spaced circumferentially relative to the rotary axis.
8. Apparatus according to claim 7 , wherein the apparatus is an axial flux device and the air-gap facing surface extends radially relative to the rotary axis.
9. Apparatus according to claim 7 , wherein the apparatus is a radial flux device and the air-gap facing surface extending axially relative to the rotary axis.
10. Apparatus according to claim 1 , wherein the first part is operative to move relative to the second part along a linear axis and the plurality of electromagnet elements are axially spaced relative to the linear axis.
11. Apparatus according to claim 1 , wherein the coil-winding sections of adjacent electromagnet elements are longitudinally offset to allow the air-gap facing surfaces of adjacent electromagnet elements to be positioned in close proximity.
12. Apparatus according to claim 11 , wherein a first set of electromagnet elements have the coil-winding section at a first longitudinal end thereof and a second set of electromagnet elements have the coil-winding section at a second longitudinal end thereof.
13. Apparatus according to claim 1 , wherein the pole piece comprises a further outer section defining a further elongate air-gap facing surface as previously defined, the further outer section being provided at an opposed end of the pole piece to the first-defined outer section.
14. Apparatus according to claim 13 , wherein the second part comprises a first section facing the first-defined outer section and a second section facing the further outer section.
15. Apparatus according to claim 1 , wherein the electrically conductive coil is wound around the coil-winding section with fewer than 5 layers of turns.
16. Apparatus according to claim 1 , wherein the electrically conductive coil of each electromagnet element is fluid-cooled by direct contact with fluid flowing over the electrically conductive coil.
17. Apparatus for use as a motor or generator, comprising:
a first part;
a second part movable relative to the first part and spaced from the first part by an air gap; and
a plurality of laterally spaced electromagnet elements provided on the first part, each electromagnet element being operative to apply a magnetic field in the air gap in response to application of an electric current;
wherein each electromagnet element comprises:
a pole piece comprising:
an outer section defining an elongate air-gap facing surface of area A 1 , perimeter P 1 , lateral width W 1 , and longitudinal length L 1 , wherein L 1 is greater than W 1 ; and
a coil-winding section of cross-sectional area A 2 , cross-sectional perimeter P 2 , lateral width W 2 , and longitudinal length L 2 ; and
an electrically conductive coil wound around the coil-winding section of the pole piece;
wherein:
P 2 is less than P 1 and W 2 is substantially equal to L 2 ; and
the outer section has a first saturation level S 1 and the coil-winding section has a second saturation level S 2 , wherein S 2 is greater than S 1 .
18. Apparatus according to claim 17 , wherein A 1 is greater than A 2 .
19. Apparatus for use as a motor or generator, comprising:
a first part;
a second part movable relative to the first part and spaced from the first part by an air gap; and
a plurality of laterally spaced electromagnet elements provided on the first part, each electromagnet element being operative to apply a magnetic field in the air gap in response to application of an electric current;
wherein each electromagnet element comprises:
a pole piece comprising:
an outer section defining an elongate air-gap facing surface of area A 1 , perimeter P 1 , lateral width W 1 , and longitudinal length L 1 , wherein L 1 is greater than W 1 ; and
a coil-winding section of cross-sectional area A 2 , cross-sectional perimeter P 2 , lateral width W 2 , and longitudinal length L 2 ; and
an electrically conductive coil wound around the coil-winding section of the pole piece;
wherein:
P 2 is less than P 1 and W 2 is substantially equal to L 2 ; and
P 2 is less than or equal to 0.9 times P 1 .
20. Apparatus for use as a motor or generator, comprising:
a first part;
a second part movable relative to the first part and spaced from the first part by an air gap; and
a plurality of laterally spaced electromagnet elements provided on the first part, each electromagnet element being operative to apply a magnetic field in the air gap in response to application of an electric current;
wherein each electromagnet element comprises:
a pole piece comprising:
an outer section defining an elongate air-gap facing surface of area A 1 , perimeter P 1 , lateral width W 1 , and longitudinal length L 1 , wherein L 1 is greater than W 1 ; and
a coil-winding section of cross-sectional area A 2 , cross-sectional perimeter P 2 , lateral width W 2 , and longitudinal length L 2 ; and
an electrically conductive coil wound around the coil-winding section of the pole piece;
wherein:
P 2 is less than P 1 and W 2 is substantially equal to L 2 ; and
W 2 is greater than W 1 .
21. Apparatus according to claim 20 , wherein W 2 ≥1.5x W 1 .