The practical success of the Battery Transformer system has been
demonstrated at Vienna, where an installation of five thousand lamps
in the Opera House and Burg Theatre was maintained for the past year
from a distributing station 1,400 yards away. The boilers are fixed
in a basement formed by excavating the court-yard of a private house
to a depth of 15 feet 6 in. below the street level; the building
itself is utilised partly for offices and partly as a large dynamo and
engine-room. Each dynamo is designed to give an output of 72 kilowatts
or 120 ampères, at 600 volts pressure. The current is led by means of a
lead-covered cable underground to the accumulators, which are erected
in groups of 52 cells each, so as to give 100 volts to the lamps, with
a comfortable margin. The total pressure required to charge the four
groups of batteries in series varies from 430 volts at the time the
batteries are giving off work, to 480 volts for the short time during
which the charge is being completed. During five hours of lighting
about two-thirds of the current comes direct from the dynamos; but
during this time, for short periods, the demand for current often
increases to such an extent that these proportions may be reversed, and
the batteries supply two-thirds of the total.
The regulation of groups of batteries placed in series is not a
difficult matter, and will be understood by referring to the following
diagram, Fig. 27:—
[Illustration: FIG. 27.]
The four battery stations mentioned as arranged in series are
represented. The current may be supposed to enter at the right hand
corner, passing through the first battery with the lamps parallel to
it, and from that battery to the commencement of the next, and so on
through the third and fourth, the current being varied at will at the
central-station, or kept constant by means of an electrical governor.
The potential for each of the four groups of lamps is maintained in
the following manner:—In each group one terminal is kept permanently
connected to one of the discharge mains and to one of the charging
mains; the other terminal can be shifted from cell to cell according to
the E. M. F. required in the corresponding lamp circuit by means of a
contact regulator. This movable terminal is shown by the bunch of lines
at one extremity of each battery group. The rule for charge and
discharge is, that the terminal cell at the regulating end of the
battery is so arranged that it neither receives nor gives off current,
so that there is no loss of energy in the shape of E. M. F. The contact
regulator, which was designed by Mr. Crompton for use at Kensington
Court, is shown by Fig. 28:—
[Illustration: FIG. 28.