Transverse-flux tubular motors

The paper describes a new range of tubular induction motors. Compared with the usual forms of tubular motors, in which the magnetic flux lies largely in planes that are parallel to the direction of motion, the new machines have flux paths lying transverse to this direction. Two winding arrangements are described; the first of these uses skewed coils that completely surround the secondary conductor, the second uses a double helical system. The excitation produced by these windings is in the form of a circumferentially modulated axially travelling wave, and an appropriate multilayer analysis using cylindrical geometry is presented. Experimental and theoretical results are given that show that the transverse-flux machine can provide more thrust than the conventional machine when the core-flux density is the limiting design factor.