Under these circumstances the
item of weight is a vital consideration. It must be kept within
a limit of 100 pounds, and the less the equipment weighs the more
satisfactory it is likely to prove, other things being equal.
The two most successful systems yet exploited are the Dubilier
and the Rouget. The former is an American invention, the latter
is of French origin. Both have been tested by the British
Military Aeronautical Department, and the French authorities
have subjected the French system to rigorous trials. Both
systems, within their limitations, have proved satisfactory.
The outstanding feature of the Dubilier system is the production
of sine waves of musical frequency from continuous current, thus
dispensing with the rotary converter. The operating principle is
the obtaining of a series of unidirectional impulses by a
condenser discharge, the pulsating currents following one another
at regular intervals at a frequency of 500 impulses per second,
which may be augmented up to 1,000 impulses per second. The
complete weight of such an apparatus is 40 pounds; the electric
generator, which is no larger than the motor used for driving the
ordinary table ventilating fan, accounts for 16 pounds of this
total.
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