. The Street railway journal . od practice determined by thesefactors. The amount of copper in the field magnet coilscan be conveniently calculated from the following formula: Ampere feet Weight / Ampere feet \of copper per spool = 31 xl - )\ 1000 / should always be of wrought iron or steel, but the yokemay be of cast iron or steel, according to the market valueof material. Laminated poles have not been a particularsuccess, since they tend to make the flux at the pole faceunstable as to surging on change of load from the coilsunder commutation. The leakage or ratio of effective to maximum flux
. The Street railway journal . od practice determined by thesefactors. The amount of copper in the field magnet coilscan be conveniently calculated from the following formula: Ampere feet Weight / Ampere feet \of copper per spool = 31 xl - )\ 1000 / should always be of wrought iron or steel, but the yokemay be of cast iron or steel, according to the market valueof material. Laminated poles have not been a particularsuccess, since they tend to make the flux at the pole faceunstable as to surging on change of load from the coilsunder commutation. The leakage or ratio of effective to maximum flux variessomewhat, but with large ring multipolar dynamos doesnot exceed 15 per cent, which may be safely assumed incalculation. Their leakage does not increase more than20 per cent between no load and full load, or 3 per cent ofthe total flux, so, with normal magnetizations, does notgreatly influence the amount of compounding. The number of poles with multiple circuit armaturewindings is determined by the maximum armature reac-. Watts per pound. Street Curves 3, 4 and 5 show the magnetic properties of com-mercial wrought iron, cast iron and cast steel. The cores FIG. 2.—CURVE EXHIBITING THE RELATION BETWEEN CYCLESPER SECOND X K1LOLINES DENSITY BELOW SLOTS ~1000 AND WATTS PER SECOND IN ARMATURECORE, BASED ON OBSERVED RESULTS INTWENTY-THREE LARGE MULTIPOLARCOMMUTATING MACHINES tion consistent with commutation, the minimum numberof commutator segments, and the maximum permissiblereactance of an armature coil, and the greatest economicalcontact resistance, and is therefore determined from thecondition determining the maximum current which can becollected at a set of brushes, which in the kind of practiceunder consideration does not exceed 300 amps, at ratedcapacity. MAGNETIC LIMIT OF OUTPUT The limit of output of a commutating dynamo from amagnetic point of view is determined from the maximumvalue; that having regard to heating can be assigned tothree independent variables.
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Keywords: ., bookcentury1800, bookdecade1880, bookidstreetrailwa, bookyear1884
