The Portland daily press. [volume] (Portland, Me.) 1862-1921, 1898-02-04
ELECTRICAL SCIENCE.
why Electric Motors Do Not Supplant
Steam Locomotives.

the impression that by the use of cleo
tricity five or six horse power will do the
work of fifty or sixty horse-powe pro-
duced by steam," said an electrician.
"Only few days ago such person said
to me in good faith that he believed that
electric motors would soon take the place
of steam locomotives for general railroad
use, because little electric motor of five
or six horse. power would be able to do
the work of the heaviest engine. The real
economy of the electric motor does not lie
in it's being able to do any more work for
each horse power than could be done by
the steam engine. but in the fact that the
power for many motors can be generated
at one central station under conditions OF
much greater economy than can be Sc
cured in the locomotive or in small sepa-
rate plants, and also in the greater ell
cheney for certain purposes of rotary
motor over the rec1procating action OF the
ordinary steam engine. Speaking gener-
ally the power all comes from coal orlgl-
nally and the steam engine Is USED TO
drive the electric generators or dynamos,
as they are called. If there were nun
dred machines to be driven and each OF
these would take fiye-horse-power they
would each require an electric motor
of the same power as if the motor were
steam engine, and the whole would re
ouire central station engine, which
would furnish to them 500 horsepower in
the aggregate. The loss of power in good
~ FOR,
cent so that the central station must &C.
tually produce, in such cnse, fifty horse
power perhaps more than the separate
steam engines to perform the same work
would be required to do You wonder,
then, where the economy OF using cleo
richly lies. Let us consider this as APP
piled to the running Of locomotives, for
instance. An express locomotive running
under favorable conditions, will use about
four pounds OF coal an hour for each
horsepower produced. Some runs have
been made upon a consumption of three
and one half pounds an hour for each
horsepower. An engine drawing local
train will burn five pounds of coal every
hour for each horsepower, while the
usual consumption of freight locomo
tive is from six to ten pounds. Even
this does not take in the coal wasted
while the engine is getting up steam, or
that burned when the fires are banked or
thrc wn away when the fires are drawn.
Compare this with the results attained
in good stationary plants. Some OF these
will produce power at an expense OF l.
hounds of coal for each horsepower an
hour, while it is q poor plant which re-
uuires more than two pounds In the new
steamship Kaiser Wilhelm der Crosse the
engines produce &c, COO horsepower upon
an average consumption of one and one
half pounds of coal for each horsepower
an hour for run across the Atlantic.
Coal can he delivered and handled cheaper
at large central stations and the other ex-
penses are also less. AS a rule the cost of
fuel on electric roads is about five per cent
of the operating expenses, While on steam
roads 1t is about ten per cent. The real
reason why the electric locomotive does
not at once take the place of the steam
motor is the difficulty and cost Of distrib
uting the electric current for long dis
tances without great loss OF current
through the electrical resistance of the
wires To overcome this the roads oper
ated by electricity are divided into short
sections. and separate copper feeder wires
are run from the power house to each SEQ
tion This would not entail go much OK
pense if it were not for the fact that each
feeder wire as 1t is increased in length
must also be increased in size OF there
would be great loss of power and the
cost of the copperssoon gets to be too great
to warrant the increase in size. When
the scheme for building the Broadway
underground rapid transit railway was
being investigated by Supreme Court
commission IN 1895 experts testified that
to transmit the enormous amout Of power
which would be required for the proposed
train service would take 81, 000,0 600 worth
of copper wire alone If the power all came
from one station.
These difficulties were set forth recently
by Claude Marshall in a paper,,read before
the Chicago Electrical Association, and
Mr.. Marshall also points ont way in
which they may be overcome. He says,
in part GAS far as an engineer can see
into the future, it Is improbable that
electricity will supplant steam for general
railroading purposes. but there are some
adoption of electricity will be great ad
avncement. In thickly settled communi
ties as parts OF the New England, North
Atlantic and Central States, the railroads
will be forced to make changes in their
service to successfully compete with the
parallel trolley lines With the present
equipment it seems that $40 or 6O0 volts
at most is the limitation of the direct cur
rent motor, and long lines can only be
operated by placing power stations at fire.
uuent intervals, say ten or twelve miles
apart. The transmission at this voltage
involves enormous losses or great expense
for copper. On one road recently tested
the voltage varied from 525 volts near the
station to $40 volts at the end Of line
seven miles distant. 1t is obvious that
for transmission alternating currents
must be employed. How necessary high
yoltages are may be seen from little
calculation on the cost of copper for line
wire. Mr.. Stillwell gives the cost Of
copper required to deliver one horsepower
at motor shaft ten miles from the genera
tor, allowing twenty per cent drop and
copper fifteen cents per pound, at 500
volts, $3.50. IS. at 10, 900 volts. 81. 95. Thus
it is seen that it costs 400 times as much
to furnish copper at 500 volts as:it does at
10 Oo0 A voltage Of 10, 900 is we'll within
the present engineering practice. 1t is
generally believed that alternating cur
rent motors are out of consideration for
| traction purposes, and it Is true that the
experiments have not been successful on
account of the low starting torque and
lack of regulation; but the improvements
which havslof late been made go far in
1,S