. Electric railway journal . Circuit-B] t-jiker. Ground While either of the test sets just described could bemounted on a truck and so made portable a water rheo-stat does not lend itself readily to being hauled aroundon account of its weight and the solution which it con-tains. A more satisfactory form of portable outfit isobtained by replacing the water rheostat with a fewframes of grid resistance and connecting a controller forcutting this resistance in and out of the circuit to getthe necessary current variation. Fig. 3 illustrates suchan arrangement. An ammeter is required only ini-tially
. Electric railway journal . Circuit-B] t-jiker. Ground While either of the test sets just described could bemounted on a truck and so made portable a water rheo-stat does not lend itself readily to being hauled aroundon account of its weight and the solution which it con-tains. A more satisfactory form of portable outfit isobtained by replacing the water rheostat with a fewframes of grid resistance and connecting a controller forcutting this resistance in and out of the circuit to getthe necessary current variation. Fig. 3 illustrates suchan arrangement. An ammeter is required only ini-tially for adjusting the resistance, after which each pointof the controller will have a definite current value, pro-viding, of course, that the line voltage is reasonablyconstant. On a road operating two general types ofequipment, let us assume that it is desired to have thecircuit breakers on one class set at 275 amp and onthe other at 325 amp. With a five-point controller,convenient current values would be 260, 270, 280, 320 and330 amp. Circuit br
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