. Electrical news and engineering . C>.v,-enl 2 Cc„-, m^U-i; 4 CA^ direction, but comes to zero at each half revolution of the can represent by a curve just what takes place in the coils orarmatures of these two forms of dynamos during the period ofone complete revolution. Just as the steam engine indicator re-presents the pressure at every part of the stroke, so our curvewill show the electro-motive force at every point of the revolution. The (electro-motive force) curve of our alternatingdynamo, starting from a line of zero potential, will rise more orless abruptly, d
. Electrical news and engineering . C>.v,-enl 2 Cc„-, m^U-i; 4 CA^ direction, but comes to zero at each half revolution of the can represent by a curve just what takes place in the coils orarmatures of these two forms of dynamos during the period ofone complete revolution. Just as the steam engine indicator re-presents the pressure at every part of the stroke, so our curvewill show the electro-motive force at every point of the revolution. The (electro-motive force) curve of our alternatingdynamo, starting from a line of zero potential, will rise more orless abruptly, depending upon the design of the dynamo to apoint of maximum positive potential, then droop, and passing theneutral or zero potential line, descends to the point of maximumnegative potential. The most desirable form of all-round work, and the one whichmost modern, well-designed alternators follow, is the sign curve,though single phase alternators, which are perfectly satis-. Paper read before Toronto No. i, Canadian Ass-i 1 of Stationary Engin Two Coil Direct Current Dynamo. factory for lighting purposes, depart considerably from this formand show a peak-topped, and some a flat-topped curve. The F. curve of our direct current dynamo differs from the alternatorfor the reason that the commutator replacing the collector ringsslips from under one brush to a position under the opposite brush,just at the moment the current in the coil is about to reverse, andinstead of descending below the zero line, it again ascends, mak-ing in a complete revolution two curves, similar to the first halfof our alternating current curve, both of which are above the zeroline. Such a curve represents a series of impulses following eachother with every half revolution, and would not make a satis-factory current for practical working. Other evils would alsocreep in, as we multiplied the number of turns to obtain the voltages, which would produce vicious and destruct
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