AN IMPROVED METHOD OF AND MEANS FOR REGULATING THE CURRENTS IN DYNAMO ELECTRIC MACHINES
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by William Robert Lake at the Office
:
of the Commissioners of Patents on the 4th July 1882. Communicated to
him from abroad by Jules Carpentier of Paris, France, Engineer
WILLIAM ROBERT LAKE of the firm of Haseltine, Lake, & Co, Patent Agents,
Southampton Buildings, London "AN IMPROVED METHOD OF AND MEANS FOR
REGULATING THE CURRENTS IN DYNAMO ELECTRIC MACHINES Communicated to
him from abroad by Jules Carpentier of Paris, France, Engineer
"
The machines which furnish electric currents by induction produced by the.
displacement of conductors in a magnetic field are now classed as magneto-
electric machines, and dynamo-electric machines.
In magneto-electric machines the magnetic field is constant, and the inductors.
consist of permanent magnets. In dynamo-electric machines the magnetic field is
variable and the inductors consist of electro-magnets.
•
In both such magneto-electric and dynamo-electric machines, however, the
immediate result of the movement imparted to the induced conductors is the
generation of electro-motive force whose intensity is absolutely independent of the
intensity, and even of the existence, of the currents of which it may become the
origin. This electro-motive force depends solely upon the linear speed imparted
to the induced conductors and the intensity of the magnetic field in which they
move. The currents which it may set up in the circuits in which are intercalated
the induced conductors depend upon the resistance of these circuits as well as upon
the electro-motive force of induction.
In the use of such machines it is important that the intensity of the currents
employed should be capable of being modified according to circumstances, but it is
bardly possible to modify the resistance of the circuits to act upon the currents
without being liable to make unnecessary expenditure of energy.
It is therefore the electro-motive forces of induction which it is necessary to
cause to vary. These variations may be the result of variations caused in the
speed of the induced conductors or in the intensity of the magnetic field. Other
particular operations may result from the special arrangements of the class of
machines employed.
Nothing can be said in general with respect to these last operations; it is
intended herein to simply consider the resources which variations occasioned in the

page_text: magnetic field are capable of procuring, The considerations which follow apply
only to dynamo-electric machines.
Assume then that we have a dynamo electric machine and that the inductors are
excited by a constant current independent of the induced current. If the machine
is revolved at an invariable speed and the inducing current traverses, without
interruption, the fixed electro-magnets, the magnetic field being itself invariable,
the electro-motive force of induction will be constant. If however by any suitable
means a series of periodical interruptions is effected in the passage of the inducing
current it will be readily understood that by reason of the inertia even of the
magnetization and demagnetization of the masses of iron constituting the fixed
electro-magnets the discontinuous current will act as a continuous current whose
intensity will bear with the continuous inducing current the proportion, t being
the effective time during which the current passes in a second. It is simply
necessary that the interruptions and re-establishments of the currents should
succeed each other so quickly, that the masses of iron have not time during the
alternations to sensibly change from a magnetic condition. This condition is
always realizable.
The present invention relates to such a method of graduation of, an inducing
current by periodical interruptions. By way of example, the said invention may
be carried into practice as follows, that is to say, presuming the regulation of a
Gramme machine is to be effected and it is desired that its poles should
automatically be maintained at a determined difference of potential. The exciting
of this machine is effected by means of an independent current produced in an
auxiliary machine. The current produced by the latter traverses its proper
inducing circuit and that of the main machine; to the two poles of the latter are
connected the extremities of a circuit of very high resistance composed of a very
fine wire wound upon the bobbins of a small electro-magnet. The armature of
this electro-magnet, when it is attracted, establishes a direct communication
between the poles of the auxiliary or exciting machine and instantaneously
suppresses the inducing current. The said armature is withdrawn from the
electro-magnet by a retracting spring whose force may be varied by means of a
suitable regulating screw. From the above it will be readily understood that the
armature-spring being tightened in such a manner that the movement will be
produced by a difference in potential between the poles of the main machine below
the maximum which it is possible to attain, by allowing the induced current to
circulate in a continuous manner, it is this same difference of potential which will
be established and be maintained automatically.
The said invention may be employed as a regulation for giving a determined
value to the electricity or energy obtained from the main machine. It will then
suffice to substitute for the derivation which acts upon the electro-magnet, a
portion even of the principal or main circuit, or to cause to act one upon the other
as in electric dynamometers, two solenoids, one of high resistance in a branch of
the main circuit, and the other of low resistance traversed by the main current
itself.
In these different cases the regulator will act exactly like a vibrating tongue
charging itself automatically the regime of periodical interruptions corresponding
to the result which it is desired to obtain. As above explained my improved
system of regulation of the electric energy consists in producing in the passage of
the inducing current a series of periodical interruptions; the current which excites
the inductors undergoes a rythinical modification obtained by making or breaking
between the poles of the exciting machine a derivation whose resistance serves a
certain purpose as I will now proceed to explain.
It seems desirable that this resistance should be rendered as feeble as possible;
but then the phenomena of extra current become very troublesome. One is
therefore led to increase the resistance of this derivation which renders its action
less efficacious.
To overcome this difficulty I render this derivation identical with the circuit of

page_text: the inductor and wind it with the inductor itself, but in a reverse direction; in
this manner the two circuits oppose each other exactly, and reciprocally annul
their effects.
In order to annul the effects of the extra current I employ the following means,
that is to say-Instead of employing two machines only, the one serving to induce
the other, I employ three or more machines which induce each other and are
graduated in such a manner that the one which is to undergo the interruptions is
as small as possible. This small machine induces a second machine, the second
machine induces a third and the third machine induces the machine which
furnishes the current to the line wire; the derivation which acts upon the
interruptor is always taken from the said line wire.
I can arrange the inducing circuit of the first machine in tension.
In all cases my improved system reduces to the desired extent the phenomena
of extra current.
The above arrangements are applicable in cases where in the same manufactory
or works it is desired to employ a number of generating machines coupled up
either for tension or for quantity-In this case I employ a single suite of exciting
machines whose regime will be regulated by the line current.
In all the installations, the interruptor may consist of any suitable electric
indicator, an electro-magnet, a galvanometer, or the like.