Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . FIGURE 18. more wire or increasing the speed of our armature wecan increase the magnetism, or number of lines of force,by sending more current through the fields, that isincreasing the ampere turns. If we wish to reverse the current flow we can do soby revolving the armature in the opposite direction,or by reversing the current through the fields. Dynamos. Having so far considered the generationof currents in dynamos, we may now consider differenttypes of dynamos and their uses. Fig. 19 shows adia
Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . FIGURE 18. more wire or increasing the speed of our armature wecan increase the magnetism, or number of lines of force,by sending more current through the fields, that isincreasing the ampere turns. If we wish to reverse the current flow we can do soby revolving the armature in the opposite direction,or by reversing the current through the fields. Dynamos. Having so far considered the generationof currents in dynamos, we may now consider differenttypes of dynamos and their uses. Fig. 19 shows adia- ELECTRICITY FOR ENGINEERS 45 gram of the wires and connections of a series principal use of this dynamo at present is in con-nection with series arc circuits. (See Fig. 7.) Thisdynamo is usually equipped with an automatic regu-lator (which will be explained later) to raise or lowerthe voltage as the number of lamps increases or. figure 19. decreases, the current remaining constant at about 10amperes. By reference to the figure, we can trace thecurrent as it flows from the 4- brush, in the direction ofthe arrows, around both field magnets and through thelamps, returning to the - brush on the dynamo. Inour elementary sketch of a dynamo we used batterycurrent to magnetize our fields; we need not consider 46 ELECTRICITY FOR ENGINEERS that any more, for in practice all direct currentdynamos produce their own magnetism by circulatingsome or all of their current through the field coils. In the shunt wound dynamo, Fig. 20, the wire in thefield winding is of such size and connected in such amanner as to have a resistance so high that only a
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