Linear motor with reduced force ripple
To further reduce force ripple of a linear motor, a primary part has a plurality of windings sequentially arranged in an axial direction and subdivided in the axial direction into groups having an identical number of windings. The sequence of the association of the windings with the phases of a multi-phase system is not repeated at least in a group of windings within the primary part as long as the winding sense of the corresponding windings in the group is maintained.
1. A linear motor comprising:
a primary part in form of a cylinder or cuboid and having a plurality of windings sequentially arranged in an axial direction and subdivided in the axial direction into groups having an identical number of windings, each of the windings associated with one phase of a multi-phase system, with the primary part being divided in the axial direction into a first section and a second section, wherein an identical number of windings in the second section is associated with each of the phases; and
a secondary part having a secondary part length, wherein an axial length of the first section corresponds to the secondary part length,
wherein a sequence of the association of the windings with the phases in combination with a winding sense of the windings in at least one of the groups in the axial direction differs from the sequence of the association of the windings with the phases in combination with a winding sense of the windings in each of the other groups within the first section of the primary part, and
wherein the sequence of the association of the windings with the phases in combination with a winding sense of the windings in the second section corresponds to the association of the windings with the phases in combination with a winding sense of the windings in a subsection of the first section having an axial length identical to that of the second section and is arranged at the end of the first section facing the second section.
2. The linear motor of claim 1 , wherein the windings are constructed for three-phase operation.
3. The linear motor of claim 1 , wherein the primary part has in the first section a number of slots N and a number of pole pairs p, with: kgV (N, 2p)≧N·p, wherein kgV indicates a least common multiple.
4. The linear motor of claim 1 , wherein the first section is axially subdivided into a first half and a second half, and wherein the windings in the first half have a different winding sense from the windings in the second half.
5. The linear motor of claim 1 , wherein a maximum travel of the linear motor is less than or equal to the axial length of the second section of the primary part.
6. The linear motor of claim 1 , wherein the secondary part comprises permanent magnets having a curved surface on a side facing the primary part and cover only a predetermined part of an axial extent of a magnetic pole τ p , and have a substantially radial magnetization direction with respect to the curved surface.
7. The linear motor of claim 6 , wherein the permanent magnets have a D-shaped contour transversely with respect to a travel direction of the secondary part.
8. A combination drive comprising:
a linear motor with a primary part in form of a cylinder or cuboid and having a plurality of windings sequentially arranged in an axial direction and subdivided in the axial direction into groups having an identical number of windings, each of the windings associated with one phase of a multi-phase system, with the primary part being divided in the axial direction into a first section and a second section, wherein an identical number of windings is associated with each of the phases in the second section,
a hollow secondary part having a secondary part length, wherein an axial length of the first section corresponds to the secondary part length,
and a rotary motor arranged in the hollow secondary part,
wherein a sequence of the association of the windings with the phases in combination with a winding sense of the windings in at least one of the groups in the axial direction differs from the sequence of the association of the windings with the phases in combination with a winding sense of the windings in each of the other groups within the first section of the primary part, and
wherein the sequence of the association of the windings with the phases in combination with a winding sense of the windings in the second section corresponds to the association of the windings with the phases in combination with a winding sense of the windings in a subsection of the first section having an axial length identical to that of the second section and is arranged at the end of the first section facing the second section.