New-York tribune., 1903-02-09
DOUBLE ELECTRIC TRANSMISSION.


DR.. Bedelrs plan for transmitting two cleo
tric currents one direct and the other alter
mating. over one set of wires has much to
commend it. The chief advantage of it Is
that by getting double service out of the con-
ductors the cost of copper is theoretically re-
auced one-half Incidentally, he makes it pos
sible 10 get rid of fluctuations in the brightness
of incandescent lights operated by the same CIR
chit which runs a number OF motors. Finally.
TO the electrician. the plan will commend itself
by its comparative simplicity When two mes
sages are sent over a telegraph wire slmul-
faneously under the duplex" system special
appliances are necessary to steer the different
currents off to the right receivers. Such appa-
ratus more than pays for itself, but it adds to
the cost of telegraphy. The ithaca inventor
gets around that necessity easily. First he
establishes two complete direct current circuits
by means of four wires. Then be couples TO-
gether one wire Of each pair for one aiternat-
ing current. and the remaining wires are con-
nected for a second current of the latter char
acter. -Four different combinations are pos
sible with his four wires. The ingenuity and
simplicity of the method are positively capt.
waiting.
In estimating the future usefulness of TINS
system of distributing current from central STA
tions one must recognize the fact that the
scheme is advantageous chiefly Of not eXclu-
siveIy) where it Is desirable to run four distinct
circuits over parallel routes. Formerly incan-
descent and arc lights were operated by dl1er-
ent circuits. and often with different kinds OF
current OF late the tendency has been toward
the employment of the same circuit and the
same kind of current-a direct current. Shop
and fan motors too, are driven by electricity
xAft more
satisfactory results can be obtained by dividing
I'D the service and doing four kinds Of WORK
with four separate circuits. the facilities which
DR.. Bedell offers will be welcome. He has him
self called attention TO the benefit to be derived
from separating motor circut from lamp
circuit. Variations in the demand for power
from one minute to the next would not then
alter the brilliancy of the light. Moreover, the
time is probably not far distant when alternat-
ing current motors will be more extensively
used than now in workshops. Or. Bedells sys-
tenn will undoubtedly encourage their introduc-
ton.
Another limitation which must be borne IN
mind is the necessity for making the four con-
ductors uniform in size. If only two currents
were TO be transmitted one pair might be large
and the other small. 1t would he both absurd
and wasteful. though, to couple big and lit
tie wire together in making up the third and
fourth circuits. One Of the most important
requisites of electrical engineering is such
close calculation of the size of a conductor that
it shall carry current without undue resist
ance and yet without costing too much. No
two currents of the four here contemplated need
have the same voltage or volume. The higher
the voltage the less would be the metal re-
quired to transmit given amount Of energy.
-s1-y- 10 ~
form of a high pressure current than as a low
pressure current over the same conductor.
Hence the voltage employed for the extra ser
vice must be computed with special reference to
the size of the wire: and it may not always prove
so convenient TO vary this factor in the COM
bination as it would be TO change the diameter
of the wire.