. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . tor which is running and that re-quired to send the same current throughit if it were standing still. The power input to the armature ofa motor is equal to the product of thevoltage at its terminals by the currentwhich is flowing. The product of thevoltage required to overcome the resist-ance of the windings {, to send thesame current through the windings withthe motor at rest) by the current rep- Counter Electro-Motive Force. An electric motor contains the sameessential elements as a gen
. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . tor which is running and that re-quired to send the same current throughit if it were standing still. The power input to the armature ofa motor is equal to the product of thevoltage at its terminals by the currentwhich is flowing. The product of thevoltage required to overcome the resist-ance of the windings {, to send thesame current through the windings withthe motor at rest) by the current rep- Counter Electro-Motive Force. An electric motor contains the sameessential elements as a generator, and,in fact, the same machine can, as a rule,be used as either a generator or a has already been explained that whenthe wires on the armature of a generatorare rotated so as to cut the lines offorce produced by the field magnets, is generated in them, and thatwhen the circuit between the brushes isclosed this causes a current to flowthrough it. In such a case the the current which it produces arein the same direction. In the case of a motor, the wires on. FIG. 20. DEVELOPMENT OF SERIES WOUND ARMATURE. quantities as shown by the correspondingfingers of the right hand. With thetliumbs and forefingers of the right andleft hands pointing in the same direction,the middle fingers will be pointing inopposite directions. It will thus beseen that the generated inthe armature winding of a motor isin the opposite direction to the currentwhich is driving the motor, and tends toprevent its flowing. On this account this resents energy lost in the armature. Thediflference between these two quantities,, the product of the counter bythe current, represents the work whichthe armature is doing by its counter of a motor is thus anindication of its output. The efficiency {, the output dividedby the input) of electric motors is usu-ally fairly high, so that the counter a motor under normal conditions is Aug
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectrailroa, bookyear1901
