IMPROVE- MENTS IN DYNAMO-ELECTRIC AND ELECTRO-DYNAMIC MACHINES
Year: 1879

page_text: LETTERS PATENT to Charles William Siemens, of No. 12, Queen Anne's Gate,
Westminster, in the County of Middlesex, for the Invention of “IMPROVE-
MENTS IN DYNAMO-ELECTRIC AND ELECTRO-DYNAMIC MACHINES,"
PROVISIONAL SPECIFICATION left by the said Charles William Siemens
at the Office of the Commissioners of Patents on the 6th November 1879.
CHARLES WILLIAM SIEMENS, of No. 12, Queen Anne's Gate, Westminster, in
the County of Middlesex, "IMPROVEMENTS IN DYNAMIC-ELECTRO AND ELECTRO-
DYNAMIC MACHINES."
My Invention relates to means of regulating the working of dynamo-electric and
electro-dynamic machines, by causing those of the one class to produce more or less
electricity according as more or less is required to overcome varying electrical
resistances in their external circuits, and causing those of the other class to produce
more or less motive power according as more or less is required to overcome varying
mechanical resistances in the machinery which they are applied to work. For this
purpose I take advantage of certain principles which are well known to electricians
and have been variously applied in electric apparatus, but not heretofore to effect
regulation of the kind which I have in view, and I so modify the construction of
the machines and the conditions under which these principles are brought into
action as to render the regulation of the machines within certain limits automatic.
In order that the nature of my Invention may be more clearly understood, I will
in the first place state generally the principles above referred to, and thereafter I
will describe the modifications which I introduce in the machines to which I apply
them for the purpose of automatic regulation. When an electrical circuit is divided
into two or more branches, each branch gives passage to a portion of the total
current dependant on the relative electrical resistances of the several branches,
the branch of greater resistance passing a smaller proportion of the current.
The amount of resistance in any branch is, other things being equal, dependent on
the length of conductor constituting that branch, and therefore when a branch
forms the coil of an electro magnet its resistance is greater the greater the number
of convolutions in the coil. On the other hand, the greater the number of these
convolutions the greater is the exciting influence of a given current on the magnet
Din 21

page_text: These principles, which are well known, I apply for the purpose of my Invention to
dynamo-electric and electro-dynamic machines in the following manner :-
Instead of making the coils of the stationary electro-magnets of these machines,
as they are usually made, to present an electrical resistance nearly equal to that of
the coils of the rotating armatures, I very largely increase their resistance, making
it amount to from eight to twelve times that of the armature coils, and I do this by
a great increase of the number of their convolutions, so as to give the circuit of each
coil a greatly increased length without reducing the sectional area of the wire of
which it consists. Also instead of arranging the connections for the coils of the
electro-magnets in the usual way so as to bring them into the general circuit of the
armature and its external field as part thereof, I arrange them so that the increased
coils from portions of a branch circuit connected to the external circuit of the
machine beyond the commutator. The machine thus modified, when employed as
a dynamo-electric machine for producing electricity from mechanical power applied
to work it, has its production regulated in the following inanner-When there
happens to be an increase of resistance in the external circuit, such as often occurs
when the electricity is applied to purposes of illumination, a larger proportion of
the current passes by the branch through the electro-magnet coils, and the electro-
magnets being thereby more powerfully excited induce more powerful currents in
the armature coils, the production of electricity being thus increased when more is
wanted to overcome increased external resistance. And, conversely, when the
external resistance is lessened, a less proportion of the current goes to excite the
electro-magnets, and the machine thus is made to produce less electricity when less
is required. When the machine arranged as I have described is employed as an
electro-dynamic machine, whereby electricity is converted into motive power, a
similar automatic regulation takes place. When, for example, owing to increased
mechanical resistance the revolving armature becomes retarded, a larger proportion
of the exciting current has to pass by the branch through the electro-magnet coils,
and the electro magnets being thus more powerfully excited exert greater propelling
force on the armature giving the machine more power to overcome the increased
resistance, and conversely, when the resistance to the machine is lessened, its electro-
magnets are more feebly excited, and the power of the machine is accordingly
reduced.
Electrodynamic engines arranged as above described may be similar in all
respects to the dynamo-electric machines which produce the electricity that works
them. In order to utilise the working currents to the best advantage, I give the
revolving armature of the electro-dynamic engine a greater electrical resistance than
that of the dynamo-electric machine by which the currents are produced. Such
increased resistance may be obtained by introducing several electro-dynamic
engines into the same circuit.
Although I have above described my Invention as applied to machines having
rotating armatures, it is to be understood that similar arrangements of resistances
and connections are applicable to reciprocating armatures or cores, or to reciprocating
electro-magnets or solenoid coils acting on stationary armatures or cores.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Charles William Siemens in the Great Seal Patent Office on the
5th May 1880.
CHARLES WILLIAM SIEMENS, of No. 12, Queen Anne's Gate, Westminster, in
the County of Middlesex. "IMPROVEMENTS IN DYNAMO-ELECTRIC AND ELECTRO-
DYNAMIC MACHINES."
My Invention relates to means of regulating the working of dynamo-electric and
electro-dynamic machines, by causing those of the one class to produce more or less
electricity according as more or less is required to overcome varying electrical
resistances in their external circuits, and causing those of the other class to produce
more or less motive power according as more or less is required to overcome varying
mechanical resistances in the machinery which they are applied to work. For this
purpose I take advantage of certain principles which are well known to electricians
and have been variously applied in electric apparatus, but not heretofore to effect
regulation of the kind which I have in view, and I so modify the construction of
the machines and the conditions under which these principles are brought into
action as to render the regulation of the machines within certain limits automatic.
In order that the nature of my Invention may be more clearly understood, I will
in the first place state generally the principles above referred to, and thereafter I
will describe the modifications which I introduce in the machines to which I apply
them for the purpose of automatic regulation. When an electrical circuit is divided
into two or more branches, each branch gives passage to a portion of the total
current dependent on the relative electrical resistances of the several branches,
the branch of greater resistance passing a smaller proportion of the current.
The amount of resistance in any branch is, other things being equal, dependent on
the length of conductor constituting that branch, and therefore when a branch
forms the coil of an electromagnet, its resistance is greater the greater the number
of convolutions in the coil. On the other hand, the greater the number of these
convolutions the greater is the exciting influence of a given current of the magnet.
These principles, which are well known, I apply for the purpose of my Invention to
dynamo-electric and electro-dynamic machines in the following manner:-
Instead of making the coils of the stationary electromagnets of these machines,
as they are usually made, to present an electrical resistance nearly equal to that of
the coils of the rotating armatures, I very largely increase their resistance, making
it amount to not less than ten times that of the armature coils, and I do this by
a great increase of the number of their convolutions, so as to give the circuit of each
coil a greatly increased length without reducing the sectional area of the wire of
which it consists. Also instead of arranging the connections for the coils of the
electromagnets in the usual way so as to bring them into the general circuit of the
armature and its external field as part thereof, I arrange them so that the increased
coils form portions of a branch circuit connected to the external circuit of the
machine beyond the commutator. The machine thus modified, when employed as
a dynamo-electric machine for producing electricity from mechanical power applied
to work it, has its production regulated in the following manner:-When there
happens to be an increase of resistance in the external circuit, such as often occurs
when the electricity is applied to purposes of illumination, a larger proportion of
the current passes by the branch through the electromagnet coils, and the electro-
magnets being thereby more powerfully excited induce more powerful currents in
the armature coils, the production of electricity being thus increased when more is
wanted to overcome increased external resistance. And, conversely, when the
external resistance is lessened, a less proportion of the current goes to excite the
electromagnets, and the machine thus is made to produce less electricity when leas
is required. When the machine arranged as I have described is employed as an

page_text: electro-dynamic machine, whereby electricity is converted into motive power, a
similar automatic regulation takes place producing increased power when more
power is required.
Although I have above described my Invention as applied to machines having
rotating armatures, it is to be understood that similar arrangements of resistances
and connections are applicable to reciprocating armatures or cores, or to reciprocating
electromagnets, or solenoid coils acting on stationary armatures or cores.
The accompanying Drawings illustrate diagrammatically the above described
mode of connecting the electrical circuits of dynamo-electric machines, and the
effects resulting therefrom, as compared with the mode in which the connections
are usually made and the results of such connections. Fig. 1 illustrates the
connections as they are usually made, A¹ representing the coils of the revolving
armature; E¹, the coils of the electromagnets of the machine, and C', the external
circuit, which, as appears from the diagram, is continuous with both sets of coils of
the machine, so that the whole of the electricity has to pass through the complete
continuous circuit. The resistances of the several parts of the circuit vary in
practice, but it is not unusual to proportion them somewhat as follows:-Taking
100 to represent the resistance of the external circuit C¹, then the resistance of A¹
will be about 40 and that of E¹ about 30. Fig. 2 illustrates the mode of arranging
the connections according to this Invention. It will be seen that the electromagnet
coils E are situated in a branch so as to form one complete circuit with the
armature coils A2, and also that the external circuit C2 is completed through the
same armature coils, The resistances in this case may advantageously be
proportioned as follows:-That of C being 100, that of A2 may be 15 to 20, and
that of E2 1100 to 1200. In comparing the two arrangements represented in Figs.
1 and 2, it is obvious that if from any cause the resistance in the external circuit
C¹ of Fig. 1 is increased or diminished the electromagnets E' undergo a corre-
sponding diminution or increase of inducing power, and consequently the electrical
production of the machine is reduced when more production is required to overcone
increased resistance, and it is increased when less production is required to
overcome diminished resistance. With the arrangement of Fig. 2, on the other
hand, when the external resistance C is increased or diminished, the amount of
current transmitted through the coils E³, and consequently the productive power
of the machine, is correspondingly increased or diminished, so that the production
is approximately proportioned to the demand.
Figs. 3 and 4 illustrate diagrammatically certain results of the two arrangements,
Fig. 3 shewing graphically those derived from the arrangement of circuit represented
in Fig. 1, and Fig. 4 shewing those derived from the arrangement represented in
Fig. 2. In these diagrams ordinates measured along the base lines c', 7, and c³, m³,
represent resistances in the external circuit, the vertical abscissae of the several
curves are measured by their respective scales, f¹ measuring electromotive force
indicated by the curves F1 and F2, q¹ representing the quantities of current in the
outer circuit indicated by the curves Q1 and Q³, and h' representing the horse-
power indicated by the curves X1 and X³, shewing the total horse-power expended
in working the machine, Y¹ and Y shewing the total horse power developed, and
Z and Z the horse power developed in the external circuit. Besides the curves
F, Q, X, Y, and Z¹, which appear in the diagram Fig. 3, there are shown in the
diagram Fig. 4 a curve M2 indicating the quantity of current through the electro-
magnet coils of the machine, and a curve H* indicating the quantity of current
through the armature coils, which is the sum of that in the outer circuit Q and
of that through the electromagnet coils M³, being the total quantity produced.
On comparing those diagrams it will be seen that while in Fig. 3 the electromotive
force F', the quantity Q1, and the horse-powers ✗¹ and Y¹ rapidly diminish as the
external resistance increases; in Fig. 4 on the other hand the electro-motive force F*
goes on increasing, rapidly at first, and afterwards more slowly as the resistance
increases, also the quantity Q and the horse-powers X³, Y", and Z undergo very

page_text: much less variation in relation to the resistance, approaching more and more to
uniformity as the external resistance becomes considerably increased.
Having thus described the nature of my Invention, and in what manner the
same is to be performed, I would have it understood that I make no general claim
to connecting the whole, or part of the electromagnet coils of a dynamo-electric or
electro-dynamic machine with the coils of the revolving armature in a circuit
branching from the external circuit, but I claim in respect of such machines,
connecting in a branch circiut complete in itself independently of the external circuit
the armature coils and the electromagnet coils, the latter having their resistance
very largely increased by a large increase of the number of their convolutions,
substantially as and for the purposes herein set forth.
In witness whereof, I, the said Charles William Siemens, have hereunto
set my hand and seal, this Third day of May, in the year of our Lord
One thousand eight hundred and eighty.
C. WILLIAM SIEMENS. (L.S.)