SYNCHRONOUS CONVERTERS

229

due to the waste'of e.rn.L, since in the circuit from collector
ring to collector ring the e.m.fs. generated in the coils next to
the leads arc wholty* or almost wholly opposite to each other.

The arrangement which I have called the two-circuit single-
yhase converter, and which is diagrammatically shown in Fig.
126, is therefore preferable. The step-down, transformer T
contains two independent secondary coils A and J5, of which
one, A, feeds into the armature over coaductor rings DiD2 and
leads OiCs, the other, B, over collector rings D3D4 and leads a3a4;
so that the two circuits da* and &3a4 are in phase with each
other, and each spreads over 120 deg. arc instead of 180 deg.
arc as in the single-circuit single-phase converter.

Fxo. 126.—Two-circuit single-phase converter.

In consequence thereof, in the two-circuit single-phase con-
verter the alternating counter-generated e.xnJF. bears to the con-
tinuous-current e.m.f. the same relation as in the three-phase

converter, that is,

V* w = 0<g12 E)

and from the equality of alternating- and direct-current power,

2 IJSi - IE,

it follows that each of the two single-phase supply currents is

i r- o.8i7 r.

It is seen that in this arrangement one-third of the armature,
from ai to ai and from % to a*, carries the direct current only,
the other two-thirds, from ai to a% andfromagto <z4, the differential

current,

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