Investigation of Novel Multi-Tooth Linear Variable Flux Reluctance Machines

Novel multi-tooth linear variable flux reluctance machines (LVFRMs) are proposed in this paper. First, the topologies and feasible primary-/secondary-pole combinations of singleand multi-tooth LVFRMs with six primary poles are introduced. Based on the analytical analysis of permeance model, the maximum average force can be obtained when the dc field and ac armature copper losses are equal. Moreover, four small teeth per primary pole (n = 4) LVFRM exhibits the largest average force. Furthermore, the electromagnetic performances of singleand four-tooth LVFRMs with N
_s
= nN
_p
+ 1 are comparatively studied using the 2-D finite-element analysis (FEA). It is shown that 6/25 primary-/secondary-pole four-tooth LVFRM can provide higher force capability and lower force ripple than that of 6/7 primary-/secondary-pole single-tooth LVFRM at relatively low copper loss. Similar to singletooth LVFRMs, four-tooth LVFRMs with N
_s
= nN
_p
± 1 exhibit more sinusoidal back electromotive force, larger thrust force and lower force ripple than those with N
_s
= nN
_p
± 2. Finally, the 3-D model of 6/25 primary-/secondary-pole four-tooth LVFRM is investigated to validate the 2-D FEA predicted results.