Note on the Calculation of Tooth Pulsation in Rotating Machines

Abstract

The magnitude of the tooth pulsations is calculated for rotary machines where both members are slotted.
(1) To calculate the permeance for fringing at the position of minimum air-gap reluctance, compare slot pitch of both members, and dran a symmetrical figure as a part of slots lying between the center line of slot of shorter slot piteh and the tooth of which the flux pulsation is to be calculated. Next, for these modified slots, apply the Carter's fringing constants, which are applicable only for the slots situated opposite to each other, and expressed graphically in this report.
By these methods, the maximum permeance is calculated accurately, for the cases which are likely to occur in practise for induction motors.
(2) Even if the tooth width is shorter than the slot opening in opposing surface, the minimum permeance is easily calculated by using the writer's experimental formula proposed in the previous report.
(3) The pulsation amplitudes calculated by these experimental formulae are checked with the test results, and compared with the approximate formula proposed by T. Spooner.
(4) In the above-mentioned methods, the saturation effects, and the effects of shortcircuited windings are not considered.