. The street railway review . be deterudneil very simi)ly by dividing the watts to be trang-nillled by tlie transudsslon voltage multiplied by the squareroot of three. Tile cross-sections of the coj)per may be taken very conserv-ali\ely al ) circular ndls per ampere for rubber lusulaleili-ables and !HHI circular ndls per ampere for paper Insulatedcables. The copper cross-section should be checked by estimat-ing the drop in voltage at mnximum load, but for the compara-tively short instances of city work it will usually be found thattile drop in voltage Is very small In a cable properly iir
. The street railway review . be deterudneil very simi)ly by dividing the watts to be trang-nillled by tlie transudsslon voltage multiplied by the squareroot of three. Tile cross-sections of the coj)per may be taken very conserv-ali\ely al ) circular ndls per ampere for rubber lusulaleili-ables and !HHI circular ndls per ampere for paper Insulatedcables. The copper cross-section should be checked by estimat-ing the drop in voltage at mnximum load, but for the compara-tively short instances of city work it will usually be found thattile drop in voltage Is very small In a cable properly iiroporlionedfor tile current It Is to carry. The largest si/.c three-conductor. lIG. 7. Transmission Cables.— As by three phase transmission a miui-muni of copper transmits a given amount of power with a givenloss, tills Is the system wliicii has lieen generally adopted fortransmission. Where the feeders are placed underground, threeconductor cables are used, the tiirec conductors being separatelyinsulated and then sunounded by a lead sheatii. Formerlyrubber was the Insulation used for this purpose, but paper hascome rapidly to the front and at present paper insulation is pre-ferred by many to rubber. Paper docs not soften under heatlike rubber, and tlie cable has the advantage of being cheapertiinn rubber and of having a soiiiewiiat greater overload weak part of any cable is tlie joint, and great caie slinuld
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Keywords: ., book, bookcentury1800, bookdecade1890, booksubjectstreetrailroads
