25

tion motors which drive the mill tandem. The complete installation
was made by an American company that has had considerable experience
 in electrifying sugar mills in Cuba.
The feasibility of complete electrical operation in a sugar mill
having been proved, other mills became interested. At the end of
1929 three more mills had completed their electrical installations.
These mills were all equipped by a German company, which obtained
the bids by offering lower prices and longer terms than its American
sompetitor. Details of the three mills which were electrified during
1928-29 are as follows:

Quear mill

Bedadreng....cocoeann
SoIMBOrO. anes sans annans

OenSENERAT maemo

Capacity of generators

Current

1,350 kilovolt amperes_............. Alternating...
saci Ousva peammmmanpenmrme pms ogin wid
1,000 kilowatts oo oooocaeooanaan. directo...
,600 kilovolt amperes... _......... \lternating...
L000 kilowatts. ooceooeeooaeooooo. Directo...
#00 kilovolt amperes....-....._..| Alternating. ..|
»Y 1,600 kilovolt amperes... __..do....._._.
3v 1,000 kilowatts. .o.oomeoooooo) Directo...
Ty 19 kilowatts ooo eceonyeee On
4by7 Bos emoeeaion aR en
»y 100 kilovolt amperes..........} Alternating...
yy 4 kilowatts. _ mcemmeeee Directo...

Voltage | Prime mover

100/23
100/231
160/225
180/220
160/225
120/990

Steam turbine,
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Motor.
Do.
Diesel motor.
Motor.

160/320
230
230
270/380
290

it is probable that other additional Java sugar mills will install
slectrical equipment, particularly if experience proves that lower
operating costs result from such installations. With world sugar
prices at their present levels the argument of economy of operation
will have a strong appeal. This same price situation, however, may
result in ducking the tendency to invest in expensive new equipment
until conditions improve.
MINING INDUSTRY

Coal mining. —FElectrical energy is used extensively in the Government
 owned and operated coal mines in Sumatra, the total installed
capacity of the mines being 9,350 kilowatts. - At the Ombilin coal
mines on the west coast, three steam turbines, one A. E. G. of 2,750
horsepower capacity and two Stork machines of 2,500 horsepower each
are installed. The A. E. G. turbine is connected to a generator of the
same make, while Smit generators of 2,000-kilowatt capacity each
are connected to the Stork turbines. The current is used chiefly to
operate the direct-current locomotives which carry the coal in the
mines and for operating ventilators and electrically driven air compressors,
 as well as for general lighting purposes.
Prior to 1921 the motive power for the Poeloe Laoet mines was
generated by steam, but this was not entirely satisfactory and two
turbogenerators of 1,000-kilowatt capacity each have been installed.
In 1927 a further addition was made when another unit of 1,000-kilowatt
 capacity was added. The three steam turbines are Stork
machines and are coupled to Smit generators. The electric installation
 at Poeloe Laoet made it possible to operate with electric motors
their pumps of 2 to 4 cubic meters per minute capacity, the lifts, and
the ventilators. An air-compressor plant for the operation of the
pneumatic-drilling machinery, with an air capacity of 3,000 cubic
meters per hour, is also operated by the power generated in the
electric plant.