Fig. 2,867.—Skeleton diagram showing wiring of alternator, exciter, transformer and converter. The cut also shows switchboard and connections.
It has practically become a fixture in all large electric railway systems and in other installations where heavy direct currents of constant pressure are required at a considerable distance from the generating plant. In such cases a rotary converter is installed in the sub-station, and being simpler in construction, higher in efficiency, more economical of floor space, and lower in price than a motor generator set consisting of an alternating current motor and a dynamo which might be used in its place, it has almost entirely superseded the latter machine for the class of work mentioned.
Ques. What is the objection to the single phase rotary converter?
Ans. It is not self-starting.
Ques. What feature of operation is inherent in a rotary converter?
Ans. A rotary converter is a "reversible machine."
That is to say, if it be supplied with direct current of the proper voltage at its commutator end, it will run as a direct current motor and deliver alternating current to the collector rings. While this feature is sometimes taken advantage of in starting the converter from rest, the machine is not often used permanently in this way, its commercial application being usually the conversion of alternating currents into direct currents.
Ques. How does a rotary converter operate when driven by direct current?