Magnetic permeance of identical double slotting. Deductions from analysis by F.W. Carter

Using the analytical results of an original, as yet unpublished, work of the late F.W. Carter, which is presented in some detail in an appendix to the paper, computed numerical values are given for the permeance per tooth pitch between two identically slotted surfaces when the teeth on one are centrally opposite the slots on the other, for a range of tooth and slot widths. By comparison with the known case when the two sets of teeth are opposite, values are given for the difference of permeance between the two positions. These numerical results are utilised to obtain the `flux-utilisation coefficient¿ in Guy-type inductor alternators as a function of dimensionless parameters characterising the slotting and the airgap. Further, a process of crossplotting gives the ratios of slot and tooth width to airgap width which make the ratio of the change of permeance to the square of the `unslotted permeance¿ an optimum, for possible use as a guideline from which to start the design of vernier reluctance motors.