Year: 1897

page_text: Date of Application (in the United Kingdom), 21st May, 1897
Complete Specification Left, 21st May, 1897-Accepted, 20th May, 1898
We, The SOCIÉTÉ GÉNÉRALE DES INDUSTRIES ECONOMIQUES, of 40, Rue Laffitte,
Paris, France, do hereby declare the nature of this invention and in what manner
the same is to be performed to be particularly described and ascertained in and by
the following statement :-
It is well known that the essential condition for the proper working of a dynamo
is that the speed of rotation shall be absolutely uniform in order that the current
may remain constant. In practice the intensity of the magnetic field remains
appreciably constant only when the dynamo is driven by a high-speed motor.
Now in most plants, the motors, and more particularly the explosion-engines, run,
in the different portions of the cycle, with considerable variations of speed, which
are always accompanied by fluctuations in the voltage of the dynamo.
These variations of electric potential have numerous disadvantages, whatever be
the purposes to which the current is put, and this is the case to a remarkable
degree in electric light plant in which they occasionally produce an absolute absence
of uniformity of the light.
The means of regulation heretofore employed, such as storage-batteries shunted
into the circuit, are onerous and difficult to keep up.
Now apparatus according to this invention is designed to regulate the magnetic
field or, rather, to compensate automatically for the fluctuations of voltage that
are produced in the dynamos as a result of the variations in the speed of their
motors.
In order to effect a simple and yet very exact regulation, we place in the induc-
tive system, series of resistances which increase or decrease according to a deter-
mined law, which is the same or very nearly the same as the law of the variations of
speed of the motor in the different periods of the cycle. These resistances, which
may be formed in any suitable way-for instance, by simple rheostats-are con-
nected to the contact-pieces of a collecting apparatus. These contacts are arranged
in the order corresponding to the law of variation of the speed. There is also pro-
vided a brush-holder having two brushes one of which is constantly in contact with
the conducting ring of the collector interposed in the inductive circuit of the
dynamo, whilst the other comes successively into contact with the several contact-
pieces of the collector.
The apparatus thus essentially comprises three parts, viz. a divided or gradu-
ated collector, resistances terminating at the said collector, and a brush-holder. It

page_text: is clear that if the collector or the brush-holder be keyed on the motor-shaft in such
a manner as to follow exactly the variations of the speed of the latter, the other i.e.
the collector or the brush-holder respectively-may be arranged relatively to the
first mentioned of these parts in such a manner that resistances proportionate to
the variations of the speed will always be included in the circuit.
By way of example, we have shown in the accompanying drawings a magnetic-
field regulator constructed on these principles.
The collector which is shown in front elevation in Fig. 1, in rear elevation in
Fig. 2, and in section (on the line X Y of Fig. 2) in Fig. 3, is fixed to the framing
of the motor by means of a support S and two rods TU. It embraces freely the
shaft B of the motor, whilst the brush-holder which is shown in front elevation in
Fig. 4 and in side elevation in Fig. 5, is keyed on the said shaft in juxtaposition to
the collector so that the brush x comes successively into contact with the several
contact-pieces a, b, c o whilst the brush y remains in contact with the con-
ducting ring A. The ring A and the contact-pieces are, as shown in Fig. 3, fixed
on an insulating core C of ebonite or other suitable material. The collector is fixed
on its support S by means of screws V V so as to enable it to be fixed in the desired
position relative to the shaft.
The brush-holder comprises two half rings F and G of copper, which carry
respectively the brushes x and y and embrace an ebonite collar E keyed on the
motor-shaft B. The current from the dynamo is received by the brush x, then
passes through a resistance depending upon the contact-piece with which the brush
is in contact, and finally returns to the dynamo through the brush y, which
is constantly in contact with the ring A connected to the circuit.
The resistances to be interposed vary, of course, according to the strength of
the field to be rectified.
If, for instance, the regulator be applied to a four-stroke cycle explosion-motor
in which the speeds of the crank-shaft and the cam-shaft are as 2 to 1, and the
apparatus be arranged on the cam-shaft, each quarter of the circle of the collector
will correspond to one of the strokes of the cycle.
The passage over the narrow-contact pieces a, b, c, d, e, f, g, h of the first
quarter of the circle, to which are connected resistances increasing in the
proportion of 2, 4, 6, 9, 12, 15, 18, and 21 units, for example, corresponds to
the period of explosion. During that period, the speed increases continually in a
very rapid manner. The difference between the initial resistance and the final
resistance is proportionate to the differences of speed at the beginning and end
of the said period. The second quarter of the circle corresponds to the period of
exhaust; the variations of speed are less and slower, so that there are arranged on
the collector four wide contact-pieces i, j, k, l to which there correspond
resistances running from 19 to 13 units, for instance. Similarly three very wide
contacts m, n, o will be required to correspond to the third period (suction-
period). And, finally, the six narrow contacts p, q, r, s, t, u, will serve for
connexion to decreasing resistances from 13 units to 1 unit, for example, for the
fourth period (compression period).
The exact keying of the collector on its support or its position relatively to the
position of the motor-shaft at the moment of ignition, must be fixed once for all.
This position may vary according to the permeability of the cores of the dynamo
driven by the motor.
It is clear that if the regulator be applied to a two-stroke-cycle motor,
each half circle of the collector will correspond to one stroke of the cycle
and will comprise a suitable number of contact-pieces with corresponding
resistances.
Moreover, the arrangement shown in the accompanying drawing has been shown
only by way of example.
As above stated, instead of causing the brushes x and y to turn, the arrangement
may be reversed-that is to say, the brushes may be fixed and the collectors be
caused to turn

page_text: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. Means for regulating the voltage of dynamos comprising series of resistances
which are inserted in the inductive circuit and which increase or decrease in
succession according to a determined law (corresponding to the law of variation
of the speed of the motor in the different periods of the cycle) these resistances,
which correct the variations of speed of the motor, being connected to the contact-
pieces of a collector upon which are shifted brushes that supply the current from
the dynamo and return it thereto after it has passed through one of the resistances,
and the brushes or the collector being driven by the motor, substantially as
hereinbefore described.
2. Apparatus for regulating the voltage of dynamos constructed, arranged, and
operating substantially as herein before described with reference to and shown in
the accompanying drawings.