The Dynamo Volume 2; Its Theory, Design and Manufacture (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1903 Excerpt: ...as in the smooth armature, since the longer the path of the lines from the pole to the armature, the less becomes the influence of the broken surface of the core. If, therefore, it be required to calculate the excitation necessary for the air-gap of the toothed armature, it is convenient to be able to divide the total permeance or multiply the total reluctance by m; hence the two coefficients Kj and K2 of 6 must first be multiplied by m. The total air-gap reluctance corresponding to one field or pole and one air-gap is then ml. is of the nature of a flux-density, so calculated as to permit of its being multiplied by the effective length of the air-gap in order to find x . The real average Bg, or the value of the induction averaged over the whole of the effective area of the air-gap, remains as before in the smooth-core armature, viz.: and should still be reckoned out in order to judge of the performance of the machine. 14. Calculation of reluctance of teeth in toothed armature.--Next must be calculated the ampere-turns necessary to carry the lines through the teeth and slots from the assumed equipotential circle A B to the unbroken circle of the core at the bottom of the teeth (fig. 219). As has been already described, the flux is divided between the two parallel paths offered by the iron teeth and slots, together with any non-magnetic spaces exist Fio. 219. ing in the line of the teeth. In order to prevent the reaction of the armature reaching an undue amount, it is advisable to work the teeth at a high density; it therefore becomes very necessary to calculate closely the ampere-turns required over the teeth,1 and in the first place to determine the proportion in which the flux divides between the teeth and slots, as fixed by their rela...