. Electric railway journal . ,suggesting that it might yet be of considerable commercialimportance. Even with the 25-kw equipment employedin the tests the efficiency of conversion was nearly 90per cent, although the power factor was low. The ex-periments, however, were so satisfactory that preparationswere made immediately for carrying them out on a largerscale and in heavy electric traction work, as hereinafterdescribed. PRINCIPLES OF THE PHASE CONVERTER Any polyphase motor can be operated as a single-phasemotor by connecting one phase to the line and giving therotor a start. The latter will
. Electric railway journal . ,suggesting that it might yet be of considerable commercialimportance. Even with the 25-kw equipment employedin the tests the efficiency of conversion was nearly 90per cent, although the power factor was low. The ex-periments, however, were so satisfactory that preparationswere made immediately for carrying them out on a largerscale and in heavy electric traction work, as hereinafterdescribed. PRINCIPLES OF THE PHASE CONVERTER Any polyphase motor can be operated as a single-phasemotor by connecting one phase to the line and giving therotor a start. The latter will then run at a speed some-what less than its polyphase speed, and at no load its speedwill be practically synchronous. From all of the primarywindings, including those not connected to the line, poly-phase current can be taken off. (See Fig. 5.) In this casethe alternating flux produced by the line current is cut bythe conductors of the rotating secondary, which may beeither squirrel-cage or phase-wound. The resulting second-. Magnet Frame of Single-Phase Commutator Motor withArmature Removed Both of these manufacturers realized that the problems ofalternating-current traction had not yet been completelysolved and that some kind of auxiliary apparatus might benecessary. Abroad the permutator, with synchronouslyrotating brushes, has been seriously proposed for tractionpurposes but it has not attracted much attention in thiscountry. Presumably the phase converter is receivingattention abroad also. By virtue of the Norfolk & West- ary current in turn produces a magnetizing force out ofphase both in time and space with the flux which producedit and having such a direction that, when combined withthe first flux, a rotating field is produced. This rotatingfield cuts the primary windings not connected to the lineand generates emf in them. Thus in a simple manner isproduced a converter for changing single into polyphasecurrent. October ii, 1913.] ELECTRIC RAILWAY JOURNAL 679 When no cur
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