The Montgomery advertiser., 1901-08-16

mechanical arrangement, the armature heinz, .placed at the top instead of the bottom of the. structure. See ngure 36 showing the 90 k. ". size. Tn ten Edison type the armature IS removed or replaced endwise. while with the T.-H. type the pole pieces are nrst re, moved, then the armature can De inteo or lowered vertically; with neavy armature can be lifted or lowered yer tically; with heavy armatures the la*- ter method is much more conveient:
 In this general type of machine the air gap is of considerable dimensions' resulting in the requirement. or expen- sive field magnets. For years engineers sought to make more economical use of materials by using toothed arma- lures, as originally typtfied in Pacin- nottPs form. The iron of the arma-
 ture could then approach very closely to the polar faces. reducing the reiuc- tance of the air gap. and allowing large increase in the number Of lines of force without any increase or nelo winding; then for given c. m. I. the speed of armature could be cores pondingly reduced; or with the speed kept as before the number of conduc- tors could be reduced in number ana increased in size. thereby increasing the current capacity of the machine. Further, the wires being impeooeo securely in iron. they would not De so | subject to dislocation or abrasion as on | the smooth core" type. Considera- ble difficulties were first experienced from armature reactions; brushes l would spark and require readjustment | for every considerable change of load. | Improving the magnetic circuit would naturally allow the armature m. m. f. | to express itself with as much increas- | ed effect as that due to the field wind | ing. These detrimental qualities have l almost entirely been removed by use l of oagsr fis d magnets, weaker arma-
 lures and by making the armature
 teeth satured with magnetism. the
 density of the lines of force being
 maintained as high as 10000 or 140,00O | lines per square inch. 1 When an armature revolves in a
 magnetic field of two poles the con-
 drntcrs cut lines 0f force twice each
 revolution. once under the north pole. | once under the south. By use of
 mu.tipolar field magnets the cutting of i these lines will occur oftener. resulting ! either in higher m. f. or increased | volume of current; whichever of thees l two gains is 6csred is determined by 1 the method of grouping ths aramture
 wires and the arrangemeIt of the
 brushes. For generating high C..
 m. f. or to get slow. speed in small machine the grouping of coils under the successive pairs of poles Is in series; on
 only two places of the commutator are | brushes needed. For large currents ;he grouping is in multiple and as many brushes are required as there
 are fold poles. The ordinary winding 1 If ring armature adapts itself for use l in field of any number of poles; a | drum. however, must be specially | wound f,r predetermined number of 1 poles. With multipolar dynamos the 1 drum armature coils can be separately
 wound in proper forms insulated and 1 D ced in position the cores; an injured
 coil can be rep aced without destroying l the entire wi1ding. Figure 37 shows a
 toothod drum arma .ure core for .our- pole field: figure 3S shows one of the q ricusly for,ned coils: the two parallel
 les are laid in slots 90 degrees apart;
 '~rre 21 number of these coils are
 Y own in location upon the core. Figure
 =" represents the completed machine. One nf tho cary demands for electric
 iehts was for shipboard use: room for f"ited m 'chines was not available. but dynamos we"e wa~ted Of sufficiently low e"e"d tN he directly coupled to hirh- er I engines. Such a set is shown in figure t1.
 (CoOVricht 1q00