An Improved System for the Generation of Electric Currents at Constant Potential,
Year: 1899

page_text: Date of Application, 29th Nov., 1899 -Accepted, 17th Feb., 1900
COMPLETE SPECIFICATION.
An Improved System for the Generation of Electric Currents at
Constant Potential,
I, GERHARD KOPPELMANN, of Schüttorf, Germany, Manufacturer, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed to be particularly described and ascertained in and by the following
statement:-
The present invention has for its object to maintain constant the potential of
current generators notwithstanding variation in the speed of rotation.. The new
invention consists in the interposition of a counter electromotive force in the field
magnet winding the amount of which electromotive force varies according as the
speed of revolution of the current generator changes. Consequently if the speed
of the generator increases, the counter electromotive force increases in proportion
or if desirable in a still higher ratio: hence the magnetic field of the generator is
weakened and its terminal voltage will remain unaltered in spite of the increased
speed of rotation of the armature.
The necessary counter electromotive force can be produced by means of an
additional machine which is either coupled to the current generator or combined
with it or else driven therefrom by means of belts, gear wheels or the like. The
additional machine can also be driven from the shaft of the current generator.
The invention is illustrated in the accompanying drawings, in which-
Figure 1 illustrates the improved system applied to a shunt wound machine.
Figure 2 illustrates the application of the new system to a machine which is
excited from an outside source.
The armature of the additional machine m is in consequence of the method of
driving in both cases obliged to undergo the same variation of speed as the main
generator M. The potential obtained from the additional machine at the normal
speed of rotation should be about half the potential of the main generator M.
As the potential of the additional machine opposes that of the shunt or that
obtained from the external source which excites the field magnet of the main
generator, the current in said field magnet circuit will be due to the difference
between these two potentials, consequently as this is only about half the voltage
which would otherwise be available the field magnet winding of the main generator
must be calculated for half the potential and double the current. The energy
which is. thereby apparently lost is preserved by the additional machine since it
runs as a motor and therefore returns to the source of power the energy which was
absorbed.
This new system may also be applied to alternating current and rotatory current
machines without departing from the principle of the invention.
The regulating system above described may also be easily applied to existing
installations. It only requires a small additional machine of suitable potential
and strength of current to be placed in circuit. As this annuls about half the
terminal voltage of the exciting source of current, the magnet coils of the main
engine must be connected in parallel in pairs, as the potential available for the
magnetising current is reduced to exactly one half.
The regulation described by means of an additional machine works like an

page_text: automatic shunt-wound regulator, only with the difference that the action is
instantaneous. This system is moreover simpler, cheaper and more reliable than
automatic shunt wound machines. By a suitable choice of machines the regulation
is absolutely reliable within wide limits.
The new system is preferably adapted:--
1. For eliminating variations of potential in existing plants.
2. For the better utilization of water and wind motors.
For lighting railway trains from the car axles.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
System for maintaining constant the potential of current generators having a
varying number of revolutions, characterized by the interposition in the magnet
winding of a counter electromotive force which weakens the magnetic field, the
amount of said counter electromotive force altering in the same proportion, or
when necessary in a larger or smaller proportion, according as the speed of
revolution of the current generator alters, substantially as and for the purpose
described.
Dated the 29th day of November 1800
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.