An electrical machine operating by switching of magnetic flux, comprising:
- a first magnetic structure;
- a second magnetic structure;
- and
- a winding;
- wherein said first and second magnetic structures being arranged movable relative to each other along a predetermined motion path;
- wherein said first and second magnetic structures have, along a closed path perpendicular to said predetermined motion path, respective sections interleaved with each other via more than 4 air gaps, parallel to said predetermined motion path;
- wherein each section being defined as the part of the respective magnetic structure situated between, as seen along the direction of said closed path, section surfaces facing two consecutive ones of said more than 4 air gaps;
- wherein, for each section of said magnetic structures, magnetic field lines go through magnetic material between said section surfaces;
- wherein said first magnetic structure presents, in a direction parallel to said predetermined motion path at each air gap, a variable magnetic permeability;
- wherein said second magnetic structure presents, in said direction parallel to said predetermined motion path at each air gap, at least one of:
- a variable magnetic permeability;
- permanent magnet poles;
- and
- magnetic poles comprising superconducting material;
- wherein a first average distance determined as an average distance between consecutive maxima of said variable magnetic permeability of a section of said first magnetic structure is equal, within 35%, to a second average distance determined as an average distance between consecutive maxima of said variable magnetic permeability of a neighbouring section of said second magnetic structure or as an average distance between consecutive magnetic poles of a same polarity of said neighbouring section of said second magnetic structure;
- wherein, for each of said more than 4 air gaps, at at least one position at at least one operation phase, an average of a component of the magnetic flux density normal to said section surface at an airgap is larger than 15% of an average of an absolute value of said component of said magnetic flux density normal to said section surface, wherein said averages are to be taken over a uniform-flux distance, wherein said uniform-flux distance being an integer, larger than 3, times said first average distance along said respective air gap in said direction of said predetermined motion path;
- wherein, for at least three of said sections of said magnetic structures, said winding having a respective loop provided either around respective section for at least said uniform-flux distance in said direction of said predetermined motion path, or along respective section along an entire closed said predetermined motion path.