Linear Synchronous Reluctance Motor

This is ongoing work and the design is confidential, so this page has no geometry, dimensions or winding details.

The problem

Most linear motors that produce high force use permanent magnets. A synchronous reluctance machine produces force from the saliency of its iron alone: the moving part (the translator) aligns itself with the stator’s magnetic field, so no magnets are needed. The catch is force. Reluctance machines have traditionally produced less force than magnet machines, and the shape of the translator iron sets how much they make.

Approach

I wrote my own magnetics solver and checked it against FEMM, an established electromagnetic finite element package. On top of the solver I wrote a topology optimizer based on SIMP (Solid Isotropic Material with Penalization), which treats each region of the design space as a variable density of iron and pushes it toward solid or empty.

The optimizer’s objective is my own: it trades thrust against smoothness of motion, so extra force does not come at the cost of force ripple. I took inspiration from Tesla’s reluctance-motor designs.

Results

In simulation, the optimized design produces more than four times the force of typical linear synchronous reluctance motors in the literature. The comparison is against published designs, mainly one developed for trains in Beijing. I am now building a proof-of-concept prototype.

My contribution

I designed the motor, wrote the magnetics solver and the topology optimizer, and validated the solver against FEMM myself.